of Trace Elements in Rocks)," Ya. D. (371F) Ul'yanova. T. M . . Pavlyuchenko. M. M.. (393F) Yudelevich, I . G . , Kirgintsev, A. N.. ProRaikhbaum, Ed., Nauka, Moscow, 1972. (344F) Spektrai. Anal Geol. 1971. vid Chem. Abstr.. Ref. Zh Khim. (1972, 3 ) . (345F) Stack, V. T., Anal. Chem.. 44 (81, 32A (1972). (346F) Starshenko. V. I., Volynskaya. M . P., Lebedev. G.. U S. Nat. Tech. Inform. S e w . N73-18524, 11 pp (1972): Sci Tech. Aerosp. Rep.. 11(9), 1045 (1973) (347F) Steiner, R. L., Anderson, D. ti., Appl Spectrosc.. 26, 41 (1972). (348F) Stempel, G. D . , !bid 27, 129 (1973). (349F) Stevens, R. K., Hodgeson, J. A,, Ana/ Chem.. 45, 443A (1973) (350F) Stromatt. R . W., Report. HEDL-SL-432. 13 pp (1972): Nucl Sci. Abstr.. 27 (2). 2327 (1973) (351F) Subramaniam. P., Tamhankar. R. V., Indian J . Techno/ 10, 380 (1972). (352F) Sugimae. A,. Hasegawa, T., Bunseki Kagaku. 22, 3 (1973). (353F) Sugimae. A.. Matsuo. Y., Japan Chem. SOC, 28th Meeting. Tokyo. Preprint. p 677 (1973); A i r Pollut. Abstr , 4, 28629 (1973). (354F) Sutton, A. L.. Havens, R . G., Sainsbury, C. L., J. Res U . S . Geol Surv.. 1, 301 (1973). (355F) Szoplik, J . , Pr lnst. Mech. Precyz.. 19 ( 1 - A ) , 21 (1971). C.A.. 76, 67814f (1972). (356F) /bid.. p 27; C.A.. 76, 67857x (1972). (357F) /bid.. p 13: C.A., 76, 677021 (1972). (358F) /bid.. p 36: C.A.. 77, 42725k (1972). (359F) Takada, K., Bunseki Kagaku, 21, 1245 (1972). (360F) Takahashi. T., ibid.. p 527. (361F) Tarasevich. N. I . , Chebotarev, V. E., Zh. Anal Khim.. 28, 1023 (1973). (362F) Tarasevich, N. I . , Zheieznova, A. A,. Abdullaev, A. A,. Vestn Mosk. Unlv Khim.. 12, 593 (1971): C.A.. 76, 67731b (1972). (363F) Tarasevich, N . I . . Zlomanova, G. G., Voronkova, L. E.,ibid.. 13, 443 (1972). (364F) Tarnovskaya. A. N , Plyushch, G. V.. Vestn. Leningrad. U n i v . . Fiz.. Khim.. ( 2 ) , 149 (1971): C A.. 76, 30374m (1972). (365F) Taylor, B. L., Phillips, G.. Milner, G. W. C.. Anai. Methods Nuclear Fuel Cycle. Proc. Symp.. 1971 237 (1972). (366F) Tikhonova, 0. K.. Otmakhova, 2. I . , Chashchina. 0. V . . Zh. Anal. Khim.. 28, 1288 (1973) (367F) Tolk, A.. Van Raaphorst, J. G., Anal Methods Nuciear Fuei Cycle. Proc Symp. 1971. 175 (1972). Treytl. W. J . . Orenberg. J. B., Marich, K. (368F) W . , Saffir. A. J.. Glick. D . , Ana/. Chem . 44, 1903 (1972). (369F) Tsimbaiist. V. G . , A n d Tekhnol. Biagorod. Metai.. 310 (1971); C.A.. 77, 15975sh (1972) (370F) Tsyganok, L. P., Chuiko, V. T., Reznik. B. E.,Mazan. L. K., Stets. T. V., Zavod. Lab.. 39, 169 (1973).
(372F) (373F)
(374F) (375F)
(376F) (377F) (378F) (379F)
(380F) (381F) (382F) (383F) (384F)
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(388F) (389F) (390F)
(391F)
(392F)
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Flame Spectrometry J.
D. Winefordner'
Department of Chemistry, U n i v e r s t y of Fiords, Gaineswlle. F / a 3267 I
T. J. Vickers2 Department o f Chemistry, Florida State Unwersity. Tallahassee. Fla. 32306
This is the third fundamental review on flame spectrometry prepared by the present authors. This review covers books, chapters, and articles published in the time W o r k supported by
USAF-AFOSR-74-2574.
* W o r k supported by f u n d s f r o m PHS G r a n t R01-GM15996. 192R
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period between Xovember 1971 and October 1973. Because of the large number of articles in the area of flame spectrometry (over ZOOO), it was necessary to use a filtering process to reduce the unwieldy number to a more manageable size. The guidelines used for this review are similar t o those used in the previous review (92A). The
A P R I L 1974
James D. Wlnefordner received his BS, MS, and PHd degrees in chemistry from the University of Illinois in 1954, 1955, and 1958, respectively. His research advisor was H. V. Maimstadt. From September 1958 to September 1959, he served as a Postdoctoral Fellow at the University of Illinois. I n September 1959 he was appointed assistant professor of chemistry at the University of Florida. In September 1965 he was promoted to associate professor of chemistry, and in July 1967 he was made full professor. He is currently chairman of the Analytical Division of the Department of Chemistry. His research interests include atomic and molecular emission, absorption, and fluorescence in flames and other hot gases; molecular fluorescence and phosphorescence of species in the condensed phase; development of sensitive, selective, accurate methods of trace analysis of metals and moiecules in materials based on the above spectroscopic methods; development of sensitive, selective gas and liquid chromatographic detectors; and development of spectroscopic instrumentation for analysis. He has published about 200 scientific papers and chapters on the above topics and given nearly 100 invited talks and seminars at international and national conferences and symposia and at universities, colleges, and industries. Since being at the University of Florida, 29 of his graduate students received PhD degrees and 12 more MS degrees. He has also had 23 postdoctoral fellows work with him. He is a member of the American Chemical Society. Phi Lambda Phi, Alpha Chi Sigma, and the American Association for the Advancement of Science. He is a past member of the Advisory Board of Analytical Chemistry, is currently on the Advisory Board of Chemical Instrumentation, and is an associate member of the International Union of Pure and Applied Chemistry Committee on Spectrochemical and Other Optical Procedures for Analysis. He is also a member of the Society for Applied Spectroscopy. He is a titular member of IUPACCommission V-4. Dr. Winefordner received the 1968 Meggers Award, the 1973 Fisher Award, the 1973 Pittsburgh SAS Award, and the 1971 Sigma Xi University of Florida Research Award.
guidelines used are: (i) most papers published in the following analytical journals are reviewed-Analyst, Analytical Chemistry, Analytica Chimica Acta, Analytical Letters, Analusis, Applied Spectroscopy, Canadian Spectroscopy, Canadian Journal of Spectroscopy, Chemie Listy, Chimie Analytique (Paris), Chemia Analityczna (Warsaw), Japan Analyst, Methodes Physiques Analyse ( G A M S ) , Spectrochimica Acta, Spectroscopy Letters, Talanta, Zeitschrif fuer Analytische Chemie, Industrial Laboratory USSR, and Zhurnal Analitcheskoi Khimii; (ii) no papers published in unreviewed journals (except for reviews and bibliographies) will be considered, e.g., American Laboratory, Research and Development, Industrial Research, Laboratory Practice, Atomic Absorption Newsletter, Spectrouision, Spex Speaker, and other trade journals, journals published by instrumentation companies, and free journals primarily used for advertisement purposes; (iii) only a few selected applications from journals other than those listed in (i) will be reviewed-i.e., if the applications contain something of fundamental interest, then they will be included in this review; (iv) the majority of articles reviewed here come from the journals listed in (i) and from other journals in which fundamental and methodological aspects of flames and of flame emission, atomic absorption, and atomic fluorescence spectrometry are discussed; and (v) no articles on atomic emission from nonflame sources will be discussed, whereas essentially all articles on atomic absorption and atomic fluorescence will be discussed whatever means of atomization is used. The authors should again state, as in the previous review, that they regret the omission of articles from Perkin-Elmer’s Atomic Absorption Newsletter, but felt it was necessary under the stipulation put forth in item (ii) above. The authors also wish to apologize to any irate authors who feel we should have included their favorite paper(s); the omission may have been a result of oversight or reasonable considerations based on items (ii-v) above. This review is divided into five sections: Reviews, Books, and Bibliographies; Fundamental Studies; Atomic and Molecular Flame Emission Spectrometry (FES); Atomic Absorption Spectrometry (AAS); and Atomic Fluorescence Spectrometry (AFS). During the past two years, atomic absorption spectrometry seems to have gained renewed interest and use, as
Thomas J. Vickers is ari associate professor of chemistry at Florida State University. He received his BS Degree in chemistry from Spring Hill College in 1961 and his PhD degree from the University of Florida in 1964. He served two years in the U.S. Army at the Physical Sciences Laboratory of the Army Missile Command before joining the staff at Florida State University as an assistant professor in 1966. He was promoted to the rank of associate professor in 1971. His research interests in analytical chemistry lie chiefly in the study of spectroscopic methods of trace element analysis, including atomic emission, absorption, and fluorescence flame spectrometry, new excitation sources for spectrochemical analysis, nonflame atomization techniques, and atomization and excitation processes in flames and electrical discharges.
unusual as this may seem, and atomic fluorescence and flame emission spectrometry seem to have held their own in terms of numbers of papers. There is no doubt that atomic absorption spectrometry has the driver’s seat in terms of applications; this was evident from round tables presented at the recent fourth atomic absorption conference at Toronto and the Colloquium Spectroscopicum Internationale XVII at Florence. Perhaps, during the next two years, other atomic spectroscopic methods will be utilized more for single-element analysis, but more likely for multielement analysis. This review will be mainly concerned with the techniques and concepts of more fundamental interest to analytical chemists.
REVIEWS, BOOKS, AND BIBLIOGRAPHIES During the past year, an excellent new publication has become available; namely, the “Annual Reports on Analytical Spectroscopy” (26A, 27A). This report is divided into three parts: (I) Fundamentals and Instrumentation; (11) Methodology; and (III) References. It consists of a thorough review of articles in the area of analytical atomic spectroscopy during 1971 (26A) and 1972 (27A).It is written in a narrative manner, has many cross references, and contains much of the pertinent data from the various abstracted papers. The editor, D. P. Hubbard, should be commended for such a fine review. The 69 papers presented at the Third International Congress of Atomic Absorption and Atomic Fluorescence Spectrometry held in Paris, September 27-October 1, 1971, have appeared in a two-volume book (73A). The papers are divided according to Theory and Methodology; Apparatus; Atomic Fluorescence; Rocks, Soils, and Minerals; Water, Agriculture, and Related Subjects; Biology; and Metals (73A). The papers by the plenary lecturers Willis (9OA), Mavrodineanu (39A), Dawson (IOA), Robin ( S A ) , Koirtyohann (33A), Rubeska ( 6 0 A ) , DeGalan (13A), and Butler ( 9 A ) , were all published in Meth. Phys. Anal. ( G A M S ) . The third international meeting was also reviewed by Belyaev ( 4 A )and Baudin ( 3 A ) . The fourth atomic spectroscopy conference was held October 29-November 2 in Toronto. The well-planned meeting consisted of 14 papers on non-flame cells, 26 papers on theoretical aspects of atomic spectroscopy, 14 papers on the analysis of environmental materials, 21 papers
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on the analysis of clinical, biochemical, and biological materials, 13 papers on advances in instrumentation, 4 papers on the analysis of forensic materials, 5 papers on emission spectroscopy, 11 papers on flame emission spectroscopy, 5 papers on surface analysis and X-ray spectroscopy, 4 papers on applications to health science, 4 papers on accuracy, precision, and statistical treatment of data, 6 papers on analytical molecular spectroscopy, 5 papers on atomic fluorescence spectroscopy, 4 papers on the analysis of metallurgical products, 4 papers on marine and oceanographic materials, 8 papers on X-ray fluorescence spectroscopy, 3 papers on the analysis of petroleum and petroleum products, 7 papers on the analysis of non-metals, 6 papers on electron microprobe analysis and 9 papers on the analysis of geological and mining materials. The 8 plenary lecturers for the meeting consisted of A. Walsh who spoke on spectrochemical analysis of metals and especially emphasized the use of sputtering techniques; T. S. West who spoke on atomic absorption and atomic fluorescence spectrometry and particularly stressed the measurement of atoms produced in liquid solutions near electrode surfaces; V. A. Fassel who spoke on the inductively coupled plasma as an excitation source for trace multielement analyses and gave many results for real samples (one author of this review [JDW], who has been a disbeliever of the ICP for analysis of real samples, was greatly impressed-perhaps the same author [JDW] should indicate an error in the previous review (92A) where Robin was credited with a statement concerning the usefulness or lack of it for ICPs in AAS and AES-actually Robin had only made the statement for AAS not AES); C. T h . J. Alkemade who gave his usual clear, succinct presentation of some fundamentals of AAS and AFS and some of the pitfalls analysts can fall into when applying theory to experiment; J. B. Willis who spoke on sampling methods for solid samples; R. K. Skogerboe who spoke on the microwave-excited plasma as an excitation source and gave some figures of merit for the system; I. Rubeska who spoke on the long-path atomic absorption tube; and J. D. Winefordner, who spoke on atomic fluorescence spectrometry, particularly the use of the pulsed laser as an excitation source. Unfortunately, the authors of this review do not believe any of the plenary lectures, invited papers, or general papers given at this conference will be published collectively. The XVII Colloquium Spectroscopicum Internationale at Florence was also an extremely well-planned meeting with many excellent general papers and plenary lectures. All of the papers, including the plenary talks, were published in a series of three booklets available to all participants a t the Colloquium. Several atomic absorption spectroscopy books have appeared in the past two years. These include the ones by Price (51A), Welz (84A), Pinta (49A), Parker (45A), and Hoda and Hassegawa (24A). Veillon (80A) has written a handbook on commercial atomic absorption instrumentation. Other books containing either chapters on atomic absorption spectroscopy or considerable reference to atomic absorption measurements include those by Robinson, Lott, and Barnard (55A), Vickers and Winefordner (81A), Wainerdi and Uken (83A), White, Erickson, and Stevens (88A), and Slayter (69A). Books and chapters on atomic spectroscopy, but not necessarily on only atomic absorption, include ones by M. Slavin (65A) and Parsons and McElfresh (47A). Numerous journal reviews on atomic absorption spectrometry have appeared in the past two years. Probably the most comprehensive and useful one for fundamental work was written by L’vov (37A). General reviews on atomic absorption spectrometry include those by Price ( M A ) , Levine (36A),Yokoyama (94A),Elwell (16A), Welz (85A), Mohai (41A, 42A), Reynolds (53A), Ando ( I A ) , Thomas (74A), Wozniak (93A), Rousselet (58A), and Yudelevich, Shelpakova, Brusentev, and Zayakina (95A). Reviews on the application of atomic absorption spectrometry to clinical and biological materials include those by Willis (89A), Schroeder (64A),Dawson ( I I A ) ,Rousselet (59A),Bek and Sychra ( 5 A ) , Meder and Mohler (40A), and Herrmann (22A, 23A). Reviews on the application of atomic absorption spectrometry to metallurgical and geo194R
logical samples include those by Guest (19A), McFarren (%A), Parrish, Tully, and Sauve (46A), Voinovitch (82A), Britske ( 7 A ) , Fbpert (56A), Nall (43A), Kolarczykova (34A), Borgnon ( 6 A ) , Debras-Guedon, Boix, and Draignaud (12A),Varcher (78A),Jahn (30A),Rusconi (61A),and Gupta (20A).Reviews on the application of atomic absorption spectrometry to a icultural and environmental samples include those by g r e s , Girard-Devasson, Gaudet, and Spuig (21A),Saarloos (62A),Thompson (75A),Varju (79A), Hoffman (25A), Ivanov and Lerner (29A), Somers and Smith (70A), Laporte (35A), Baltes (2A), and Faithful1 (17A). Other general papers on atomic absorption spectrometry include those by Kirkbright and Johnson (31A)on the application of indirect methods of analysis in AAS, and by Tschopel (77A) on problems and methods of microanalytical element determinations. As surprising as it may seem, a paper (52A) even appeared on “how to write a paper on atomic absorption spectrometry.” Paus (48A) and S. Slavin (68A-7OA) have given extensive bibliographies of the atomic absorption and atomic spectroscopy literature, respectively. DeGalan (14A) and Rossi (57A) have reviewed flame emission spectrometry. Duffer (15A) has reviewed atomic absorption and flame emission spectrometric methods for paint analysis. Ghodsi (18A) has reviewed several physical phenomena in flame spectrometry. IUPAC (28A) Commission V-4 has developed nomenclature, symbols and units and considered their usage for spectrochemical analysis, particularly gor general emission spectrometry and for flame spectrometry. The above-mentioned reviews primarily concern atomic absorption spectrometry but in some cases also concern various aspects of atomic fluorescence and flame emission spectrometry. Several reviews, but not necessarily concerning only AAS, FES, or AFS, have also appeared and should be mentioned. These reviews include the ones by Busch and Morrison ( 8 A ) on multielement flame spectrometry, by Santini, Milano, and Pardue (63A) on rapid scanning spectroscopy, by Wilson (91A) on the performance of analytical methods, and by Tolg (76A) on the methods and problems of sample treatment, separation, and enrichment in the case of extreme trace analysis of elements. Review papers specifically on atomic fluorescence spectrometry include those by West (86A), Kirkbright and West (32A), Sychra and Kolihova ( 7 I A ) , and West and Cresser (87A).Omenetto, Fraser, and Winefordner (44A) have reviewed pulsed source atomic fluorescence spectrometry, and Svoboda, Browner, and Winefordner (72A) have reviewed the shapes of analytical growth curves in AFS, FUNDAMENTAL S T U D I E S Most of the articles referred to in this section are concerned directly with flame spectrometry. However, in a few cases, the articles do not concern flame spectrometry directly, but the authors of this review feel that they may have application in flame spectrometry and/or interest to atomic spectroscopists. Atomization in Flames and Furnaces. Kalff and Alkemade (202B) determined the dissociation energies of some alkaline earth (hydro-) oxides in CO/NO flames by means of emission spectrometry and obtained: Do(Ca0) = 3.75 eV; Do(Sr0) = 4.06 eV; Do(Ba0) = 5.30 eV; Do(Ca0H) = 4.44 eV; Do(Sr0H) = 4.38 eV; and Do(Ba0H) = 4.88 eV. Dissociation energies of 249.0 kcal/ mole for A120 and 118.6 kcal/mole for A10 were obtained by Hildenbrand (I65B) using mass spectrometry; ionization potentials of A10 and A120 were found to be 9.53 eV and 8.20 eV, respectively. Muradova and Muradova (253B) have defined the absolute concentration of Zn atoms in the gaseous phase by using atomic absorption measurements. Friswell and Jenkens (133B) used atomic absorption spectroscopy to follow the concentrations of lead and hydrogen atoms as a function of distance from the reaction zone in flat, premixed H2-02-N2 flames; in fuel-rich flames, the added lead exists mainly as Pb atoms, whereas in fuel-lean flames, the lead exists mainly as PbO which was found to have a bond dissociation energy of 382 kJ/mole. Newman and Page (259B) measured
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the intensities of the aluminum resonance doublet and of the A10 bands for aluminum added to a H2-02-N2 flame; the bond dissociation energy of A10 was found to be 601 kJ/mole. Jensen and Jones (193B), using emission spectrometry, determined the iron containing species in fuelrich, premixed atmospheric pressure laminar H2-02-N~ flames to which iron was added; the principal compound formed by iron under these conditions was found to be FeOH. Farber and Srivastava (124B) studied by mass spectrometry the reactions of tungsten and molybdenum with potassium seeded atmospheric H2 0 2 flames and found that such species as KHMo04, K2 0 0 4 , KHW04, and K2W04 were formed. Hastie (151B)using mass spectrometry, measured the reactive intermediates (species greater than 10-5 mole fraction) of atmospheric CH4-02 and c H 4 - 0 2 - N ~ flames. Rasmuson, Fassel, and Kniseley (291B) have written an extensive paper on the formation of free atoms from aerosols of metal-containing solutions introduced into C2Hz-NzO flames by: (i) inference from well-defined reactions and equilibria in cooler flames; (ii) calculations employing a thermodynamic flame model; and (iii) experimental observations of relative free atom concentrations in the flames as a function of stoichiometry and height. The calculated partial pressures of the major flame gas species and some of the minor species (radicals) were calculated as a function of the flow rate of N20-to-CzH2 (designated p ) . Predicted concentrations of Na, Mg, Ca, Fe, Li, Be, Al, W, Ti, and Si as a function of p were compared with measured free atom absorbances in an Ar-shielded C ~ H Z - N ~flame. O Rasmuson, Fassel, and Kniseley (291B) have come to the same conclusion as one of the authors of this review (JDW) did in a previous paper in which a CzHz-air flame was used, namely that the metal atomization degree can be described by equilibrium calculations. Also, the present authors state that when solute vaporization is complete, there exists a p a t which atomization is essentially complete for metals of high ionization potential and which forms compounds with dissociation energies of 7 6.5 eV and that certain metals may form carbon containing com ounds in the interconal zone. Jensen and Jones (194B), ‘& means of spectrophotometric studies, determined the gas phase Fe-containing species in fuel-rich premixed atmospheric pressure flames of H2-02-N2 to which Fe is added. The principal compound found was FeOH; the standard zero-point enthalpies for FeOH(g) and FeO(g) from Fe(s), Oz(g);and H2(g) were found to be 69 f 20 and 259 f 20 kJ mol- , respectively. Taylor, Bartels, and Crump (337B) determined the efficiency of aspiration of metal particles in oils and the efficiency of vaporization and atomization of the particles as a function of particle size, fuel-to-oxidizer ratio, and flame type; metal atomization was found to be critically dependent upon the fuel-to-air ratio in contrast to organometallic standards. Kito, Ishimaru, Kawahara, and Sakai (213B) have determined the burning rate of residual carbon particles generated from the spray combustion flame of heavy fuel oil droplets and have obtained excellent correlation with theoretical results. Human and Strasheim (179B) studied the degree of self-absorption of spectral lines emitted by a primary flame from the degree of absorption occurring when radiation of the primary flame is passed through a secondary absorption flame. Assuming a certain primary source model, theoretical analytical growth curves were calculated, and the sensitivity of absorption was found to depend greatly upon the distribution of ground state atoms in the primary flame. Using their model, results for a spectral line with no hyperfine structure (Ca 422.7 n m ) agreed quite well with results obtained from conventional AAS with a hollow cathode lamp as the primary line source. Ghodsi and Van Severen (136B) from measurements of flame temperatures of H2-air and CzHz-air flames and an empirical equation determined thermodynamic constants for the formation of several oxides in flames. These authors accounted for the effect of solution viscosity. They found that in no case could they assume that the elements and their oxides reached equilibrium within the flame gases. Coker and Ottaway (83B) and Coker, Ottaway, and Pradhan (84B) have reported on the formation of metal
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atoins -in several analytical hydrocarbon flames. They concluded that in hydrocarbon flames, the ground state population of atoms and the mechanism of formation are both dependent upon the flame stoichiometry and the nature of the solution, and also that in the presence of interfering elements, the “interelement effects” will also depend on the same factors. These authors like Ghodsi and Van Severen (136B)assumed the flame produced metal species were not in thermodynamic equilibrium but depended upon reaction mechanisms. These results are somewhat surprising based on papers which indicated thermodynamic equilibrium reviewed in the previous review (95A). Hayhurst and Kittelson (154B) determined the H-atom concentration in H2-02-Nz flames into which alkaline earths (Ca or Sr) had been introduced. By measuring the ratio Z M + / Z ~ ~ H +where , ZM+ is the alkaline earth ion mass spectrometer ion current and I h l o ~ +is the alkaline earth monohydroxide ion mass spectrometer ion current, the H-atom concentration profile was determined. Good agreement with the CuH method for H-atom concentration was obtained by these workers. The decay of a transient atomic population above a non-flame cell has been studied by several workers, including Reeves, Patel, Molnar, and Winefordner (292B), Aldous, Mitchell, and Ryan (6B), Dagnall, Sharp, and West (98B), and Torsi and Tesari (342B). The first group (292B) studied the atom population-height profile for Ag, Cr, Cu, Fe, Mn, Ni, Pb, Sn, and Zn for both Ar and Ar-H2 atmospheres. The rate of decrease of atomic population with height was considerably less in the presence of the H2-diffusion flame and improved sensitivity and detection limits resulted. The second group ( 6 B ) developed a computer-controlled atomic absorption spectrometer to study the transient atomic population above a Delves cup, and showed that area measurements of absorbance-time profiles resulted in better precision than peak absorbance values. The third group (98B) measured transient atom populations above a Pt-loop atomizer by atomic fluorescence and atomic absorption spectrometry using photon counting and a dc amplifier. The dc system used by these authors resulted in poorer signals and distorted analytical curves as compared with the faster responding photon counting system. The final group of authors (342B) studied the influence of heating rate on analytical response for a graphite rod atomizer in atomic absorption spectrometry. With an instrumental AA system with fast response and good noise rejection, the influence of input power to the atomizer on the analytical sensitivity was studied using Cr as a probe for graphite rods of different geometrical dimensions. A theoretical model which required linear response between peak absorption and input power was developed; the authors indicated the possibility of obtaining kinetic information concerning the vaporization of atomic species from such a model. These authors also obtained a detection limit of 2 pg for Cr. Schuster (306B) has used a King furnace for vaporization and atomization of samples and electron impact for excitation of the resulting atoms. Limits of detection for Cd, Mg, Hg, and B ranged from 0.3 pg for Cd to 6 ng for B. This system was used to determine traces of elements in spectral graphite and to study the transport of material between electrodes in a high voltage spark. Surskii and Avdeenko (334B) used atomic absorption spectrometry to study the evaporation of graphite impurities and to determine the thermal dissociation of metal carbides; the heat of dissociation of aluminum carbide was found to be 327 kcal mole. Gough, Hannaford, and Walsh (140B) used catho ic sputtering as an atomizer for atomic fluorescence spectrometry. The discharge operated with a water-cooled cathode specimen and a flow-through gas control system. Linear analytical curves resulted for Cu, Mn, and Si in some iron-based alloys. The detection limits were of the order of 20 ppm, 70 ppm, and 400 ppm, respectively, and the precision was about fl%. The system should be applicable to multielement analyses. These authors also discussed some fundamental considerations for the production of atomic vapors by cathodic sputtering and the cathodic sputtering of alloys. Details of their Pyrex glow chamber were also given. Stirling and Westwood (328B) studied the dc sputtering of aluminum alloys in the pres-
d
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ence of Ar-02 gas mixtures by the use of atomic absorption and atomic emission spectrometry. Nebulization a n d Aerosol Formation. The dispersion of spray droplets in flames has been investigated by Newman and Page (260B); the ionization produced by KCl sprayed into a flame was not uniformly distributed because of the slow evaporation of the crystals and the resultant diffusion of the vapor into the flame bulk. Clampitt and Hieftje (79B) used a discrete droplet generator to measure the rates of desolvation for isolated droplets of water, methanol, isopropanol, carbon tetrachloride, and cyclohexane in an air-acetylene flame. Comparison of the measured droplet desolvation rates to those predicted by existing theories indicated that droplet desolvation was controlled primarily by thermal means which depended upon thermal properties and composition of both the droplet and the flame. The predicted model portrayed droplet evaporation to be controlled by conduction of heat to the droplet surface through the flame and through a film of solvent vapor surrounding the droplet. Omenetto, Hart, and Winefordner (272B) studied scattered light in both turbulent and laminar flames using both line and continuum sources of excitation. The wavelength dependence, the angular distribution, and the polarization characteristics of the scattered light were studied, and only for laminar flames did the wavelength dependence of the scattered light approach the A - 4 Rayleigh dependence. Also, contrary to the predictions of the theory for Rayleigh scattering, the scattering was not symmetrical about 90". In atomic fluorescence spectrometry with continuum excitation sources, the relative scattering to fluorescence signals can be greatly reduced by crossed-polarizers. Cheng, Frohligher, and Corn (71B) formed an effective means of stabilizing an aerosol by means of a fluidized bed of Teflon beads. Yalamov and Metelkin (365B) derived an equation for the velocity of aerosol droplets. Johnson and Smith (198B) developed a simple method of determining the absolute amount of metal salt added to the flame in the form of a spray; their method utilized both steam nucleation and hot water scrubbing to remove the salt aerosol from a gas stream. Souilliart, Mermet, and Robin (320B) described an ultrasonic nebulizer for flame emission work. Kelly and Sengers (205B) developed an extensive kinetic theory for the mass flux of a liquid droplet surrounded by its pure vapor. Krier and Wronkiewicz (218B) experimentally studied the development of the flame zone surrounding spherical hydrocarbon fuel droplets burning in air. These authors compared their data to existing quasisteady theories which predicted mass-burning rates and flame zone locations as a function of droplet size and found that only during part of the droplet lifetime did the quasisteady theories predict the observed mass-burning rates and that no theories predicted the correct flame standoff distances. By means of a simple heat mass transfer analysis, the authors showed that the D2-law was not necessarily a good test of the correctness of the burning rate equation as derived in the past, and so a new mass-burning rate relation was derived. Pleskach (284B) studied the evaporation rate of phosphate containing aerosol particles in flames. The ignition of flammable atmospheres by small amounts of metal vapor and particles was studied by Tolson (341B); discharges between electrodes of some low melting point metals resulted in ignition of flammable gases at much lower arc energies than with other metals. Jagoda and Weinberg (191B)discussed a device to initiate electrically-augmented flames. Fells, Fletcher, and Wilson (127B) have studied the voltage needed to initiate an electrically augmented propane-air flame between a copper anode and a pointed graphite or tungsten cathode; the minimum initiation voltage occurred a t the stoichiometric propane-air ratio, Le., at the highest flame temperature, and decreased with increasing gas velocity. Lucquin and Antonik (234B) studied the multistage ignition of hydrocarbon combustion. Bradley (46B) studied the "atomization" of liquids by high velocity gases. Williams (361B) has reviewed the combustion of liquid fuels. Flame Structure. Mizutani and Kakajima (247B, 248B) determined the burning characteristics of fuel 196R
vapor-drop-air systems using an inverted-cone-flameburner apparatus and using a cylindrical combustion vessel. A small amount of kerosene drops added to a propane-air mixture intensified the burning process, accelerating the burning velocity and the fuel-to-air ratio. Pittam and Pilcher (283B) determined the heats of combustion of the gaseous alkanes, C1 to C4 at 25 "C and 1 atm pressure using a flame calorimeter. Basevich, Kogarko, and Furman (27B) studied the mechanism of the combustion of methane and measured the concentrations of the 0, OH, and H radicals by ESR as well as stable flame gas products by gas chromatography in an atomic flame of methane. The concentrations of the reaction products of CHI as well as the products of oxidation of Hz, HzCO, and CO in comparison with the experimental values were calculated with an error corresponding to the accuracy of the reaction rate constants. Jones, Becker, and Heinsohn (197B) developed a computer-simulated model of an opposed jet cH4-02-N~ diffusion flame which included a realistic set of chemical reactions and realistic transport properties. The predicted concentration and temperature profiles agreed well with experimental results. When an electric field was imposed on the flame, the concentration and temperature profiles were predicted to shift slightly toward the cathode. Andrews and Bradley (13B) have given an excellent critical review of the different experimental methods for measurement of burning velocity. This review is concerned primarily with the maximum burning velocity of CH4-air mixtures which was listed as 45 f 2 cm/sec at 1 atm and 298 "K. Andrews and Bradley (14B) also determined in a separate paper, using the bomb hot wire and corrected density ratio methods, the variation in burning velocity with equivalence ratio for CH4-air mixtures at 1-atm pressure; the influence of pressure and unburnt gas temperature upon burning velocity are also discussed. Andrews and Bradley (15B) used the double kernel method of measuring burning velocities of CHc-air and Hz-air mixtures over a wide range of mixtures; the results were in good agreement with the nozzle burner, Schlieren angle, particle track method of measuring burning veldcities. Peschel and Fetting (279B) studied the laminar burning velocities of CH4-02 mixtures and demonstrated that the flame pressure method of determining flame velocities was not accurate. Data and Reed (105B) performed detailed flame structure studies to analyze the stabilizing region of a fuel-rich CH4-air flame with and without vitiation of the secondary combustion air; detailed temperature, burning velocity, and composition measurements were given, and heat release rate distributions and species fluxes were derived from these measurements. Datta, Hayward, and Reed (104B) also studied the flame structure of the stabilizing region of a near stoichiometric laminar burner CH4-air flame. Detailed temperature, velocity, and composition measurements were given covering a 2-dimensional stabilizing region as well as heat release rate distributions. The lack of intermixing of ambient air with the flame gases was strong evidence in support of the flame-stretch theory of blow-off. Gunther and Janisch (144B) measured by means of the particle track method, the burning velocity in a flat flame front of CHd-air, Hz-air, and CO-air mixtures at an initial .temperature of 293 O K and 1-atm pressure; the burning velocit y of a fuel-oxidant system varied with mixture composition, temperature, and pressure. Gunther and Janisch (144B) warned the reader that the experimental data could be affected by curvature of the flame front, heat losses to the burner and parallel to the flame front, or intermixing of the mixture with the surrounding atmosphere. McCormack, Scheller, Mueller, and Tisher (240B) used normal and Schlieren photographs to determine the propagation of combustion in vortex rings formed of premixed propane-air or propane-oxygen flames. Lovachev (2338) described the mechanism of flame extinction induced by convection. Bledjian (38B) described a more general formulation of the time-dependent approach to compute the speed of plane, laminar, cylindrical, and spherical flames (hydrazine and ozone decomposition flames). He also gave a means of obtaining minimum ignition energies of flam-
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mable mixtures based on multireaction kinetics and estimated a n appreciable decrease in burning velocity when the flame radius became of the same order as the flame thickness. Basu and Bhaduri (28B) studied a possible mechanism of turbulent flame production and have shown that as a flame became more turbulent (higher Reynolds number), the flame front became wrinkled, and then for even more turbulent conditions, the formation of homogeneous pockets on the flame front occurred. At very high flow rates, the flame front disintegrated. Otsuka and Niioka (273B) used a counter-flow burner to stabilize onedimensional diffusion flames of large size. A one-dimensional diffusion flame, produced by placing a porous plate a t the burner outlet, had a concentration and temperature variation in only one direction. From temperature measurements by the deflection method, the transition point, where the stretch rate suddenly changed, also resulted in a sudden change in temperature, and the most stable diffusion flame was stabilized for those conditions resulting in the maximum temperature. Mizutani (2463) showed that for turbulent combustion, the flame velocity increased greatly compared to less turbulent combustion. The turbulent flame velocity was determined precisely over a wide range of conditions by combining a semiempirical relation representing turbulence amplification by a flame. Britske, Sukach, and Saveleva (51B)studied the structure and physical properties of flames. McCreath, Roett, and Chigier (24IB) described an inexpensive technique for measurement of velocities and size of particles in flames. The method consisted of superimposing two photographs separated by a variable time interval. Newman and Page (260B) measured the flame velocity of H2-02-N2 flames containing KC1 solution droplets; these authors showed that for a gas velocity of 17 m/ sec, a particle of radius 1 x 10-6 m would adjust to the gas velocity in less than 2 cm, whereas a particle of radius 1 x 10-5 m would not adjust to the gas velocity until 2 5 cm above the burner top. Therefore, measurements of gas rise velocities with large particles of magnesia or alumina could result in overestimates of the flame gas velocity especially in the lower half of the flame. Knapton, Stobie, and Krier (2I4B) investigated burning rates of fuel-air mixtures (J-P-4 fuel) at high pressures (2000-4000 psi); they found that a wide variation in burning velocity resulted with maximum burning velocities occurring at minimum fuel-air mixing times. Strauss and Scott (330B) measured detonation wave speeds and pressures for H2-02 and H2-NO mixtures a t initial pressure up to 40 atm. Bowser and Weinberg (45B) and Jaggers, Bowser, and Weinberg (190B) studied the effect of electric fields on the burning velocity of CH4-air flames and concluded that the effects of dc and rf fields parallel to the direction of flame propagation do not produce any appreciable changes in the burning velocity. Ponizko and Rozlovskii (286B) determined the limits of flame quenching. Morrison and Scheller (250B) studied the effect of burning velocity inhibitors on the ignition of hydrocarbon-02N z flame mixtures; 20 additives including SnC14, GeC14, SiC14, cc14, SiC13H, PC13, AsC13, TiC14, CH31, CH3Br, CH3C1, CHBF, CHBr3, Br2, Cl2 BBr3, Cr02C12, POC13, and Fe(C0)5 were studied. The SnC14 and GeC14 additives increased the ignition temperature of propane-air systems, whereas Sic14 did not affect the ignition temperature and ccl4 lowered it. The other additives also either increased the ignition temperature of CH4-air or propaneair systems, decreased it or had little effect on it. Possible mechanisms for the experimental results were given. Spalding, Stephenson, and Taylor (321B) used a calculation procedure for prediction of the flame speeds of onedimensional unsteady laminar flames. Aldous, Bailey, and Rankin (4B)measured the burning velocity of premixed C2H2-N20 flames and studied the influence of burner design on burning velocity. These authors discussed the analytical use of burners for the C2H2-K2O flame and indicated the tradeoffs needed between a cool burner with small orifices to minimize flashback US. the transport efficiency of aerosol into the flame. By means of stainless steel capillary burners, it was possible to overcome most of the disadvantages of slot burners for C ~ H Z - N ~flames. O Woodward and Drew (363B) de-
scribed a flame quenching device with non-parallel walls for measuring accurate quenching distance data. Ewins (122B) studied the stabilization of flames at multiple cylindrical posts. Sriramulu, Gupta, and Heitland (322B) studied some peculiarities of flames stabilized in pulsating streams; the pulsations introduced into the fuel-air mixture always shortened the recirculation zone, measured by introduction of NaCl into the zones (photographic measurement of the entire flame region near the burner top). Conolly and Davies (87B) studied convective heat transfer from flames and had some success in relating the forced convective heat transfer from high temperature flames to the thermophysical properties of their combustion products. Gray, Gray, and Kirwain (142B) have written an extremely interesting article on the application of combustion theory to biological systems; the systematic application of combustion theory to problems of bioenergetics is a fieId which has hardly been exploited. In both combustion and living systems, there is a balance between the generation and loss of heat and only when these two quantities are equal, is it possible for a steady state to exist. For certain critical conditions including hypothermia, hyperthermia, and hibernation, the steady state is not achieved. The existence of the body temperature for optimum stability from the combustion theory viewpoint and the distribution of temperature in self-heating tissues were also discussed as was the parallel between flame propagation and nerve impulse, both having a characteristic velocity and a non-linear positive feedback process. Fissan (131B) discussed the thermal state of an open stoichiometric premixed CH4-02 flame by measuring the OH emission. By measurement of the population distributions in several planes of the flame for the rotational energy levels of the three vibrational levels of the 22: state of OH, the population distributions were characterized by a population temperature. The rotational temperature of the u' = 2 vibrational level deviated from all other population temperatures as well as temperatures measured by the emission-absorption method using either the 306.4-nm OH bandhead or the Na 589.0-nm line. Holmstedt (169B) determined the upper limit of flammability of H2 in air, 02, and 02-inert gas mixtures at pressures between 0.97 and 29 atm using two cylindrical bombs. Crittenden and Long (95B) measured the concentrations of all identifiable stable species ranging from hydrogen to polycyclic aromatic hydrocarbons for fuel-rich premixed flat flames of acetylene and ethylene. Chomiak (77B) measured transient local chemiluminescence in combustion regions and determined the flame structure of flames produced from homogeneous air-fuel mixtures of high Reynolds numbers; chemi-ionization was also measured. The basis of chemiluminescence measurements in flame structure studies was: since the rate of production of excited molecules was proportional to the rate of chemical reaction and since the radiation emitted was spontaneous and occurred after a very short relaxation time, it could be assumed that the local chemiluminescence intensity was proportional to the mass rate of chemical reaction a t the point considered, especially for a homogeneous mixture of constant composition, temperature, and pressure. Feugier (129B) and Park and Appleton (276B) determined soot oxidation rates in laminar hydrocarbon flames by means of an optical method and by means of shock tube measurements, respectively. Cotton, Friswell, and Jenkins (93B) examined the mechanism of soot removal by metallic additives (40 metals) in a propane diffusion flame; the mechanism for the alkaline earth metals involved a homogeneous, gas-phase reaction with flame gases to produce hydroxyl radicals which rapidly removed soot or soot precursors. However, other metals probably involved other mechanisms. Uhlherr and Walsh (347B) studied currents produced in dc electrical discharges in seeded- and unseeded-propaneair-flames. Radiational Excitation a n d Radiational or Non-Radiational Deactivation i n Flames. Hollander, Lijnse, Franken, Jansen, and Zeegers (l67B) and Hollander,
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Lijnse, Jansen, and Franken (168B)studied the quenching of excited strontium atoms in HZ flames and in CO-Nz0, CO-02-Ar, and Hz-Oz-CO2-Nz flames, respectively. By measuring the quantum yield of Sr (460.7 nm) line in flames as a function of gas composition and temperature, the quenching cross-sections for various flame gas species were determined. The cross-sections for HzO and OZ appeared to be anomalously high. Lijnse (226B) and Lijnse and Van der Maas (228B) determined the temperature dependence of the quenching of the Na-D doublet by Nz molecules and by Hz and 0 2 molecules, respectively. Lijnse and Elsenaar (227B) studied the temperature dependence of the quenching cross-sections of the Na-D doublet by Nz and HzO molecules in H2-0z-N2-Ar flames having temperatures ranging from 1500 to 2500 “K; the Nz and HzO .cross-sections were independent of flame temperature and were found to be 22 x 1 0 - l S m2 and 2.2 x 10-’6 m2, respectively. Lijnse, Zeegers, and Alkemade (2298) measured cross-sections for quenching and doublet mixing of R b ( 5 2 P 3 / ~ , ~ doublet /2) by Nz, 0 2 , H2! and HzO. The quenching cross-sections decreased with increase in flame temperature. Browner and Winefordner (55B) studied the temperature effect of pressure broadening on several indium lines. No reasons could be given for the observed variation of collision half-width with temperature; similar effects for Fe and S n were also observed. Bleekrode and Van Benthem (39B) studied the resonance fluorescence of Mg vapor in the presence of various gases and estimated quenching cross-sections from Stern-Vollmer plots. Fisher and Smith (130B) determined the cross-sections for quenching of electronically-excited alkali atoms by Nz and found that the cross-section was insensitive to the vibrational level of the Nz molecule and to relative translational energy within the framework of the ionic intermediate quenching model, and so the discrepancy between measured cross-sections of high temperature flames and low temperature fluorescence measurements remained unresolved. Time resolved atomic absorption spectrometric measurements have been used by Husain and Littler (182B) and by Husain, Kirsch, and Wiesenfeld (180B) to determine the collisional quenching of electronically-excited P b and N species, respectively. The atomic species were generated by pulsed irradiation of lead tetraethyl and nitrous oxide. Heidner and Husain (158B) and Heidner, Husain, and Wiesenfeld (I60B) have used time-resolved atomic absorption spectroscopy in the vacuum UV to study the collisional quenching of excited 0 atoms by Hz, Dz, NO, NO2, N20, CHI, and C3O2. Time-resolved resonance fluorescence was used by Strain, McLean, and Donovan (329B) to determine the quenching rate of excited iodine atoms by C3Hs and CD4. Chenier and Lombardi (72B) used the Hanle effect of the 228.8-nm Cd resonance fluorescence line of Cd atoms sprayed into an atmospheric flame to determine the magnetic depolarization of atomic fluorescence. Chiu (73B) has derived the multipole-multipole quenching cross sections for collision between excited atoms and molecules. The results of a quantum mechanical formulation of resonance fluorescence was given by Carrington (66B). Colver and Weinberg (85B) studied quenching of magnetically rotated augmented flames and plasma jets in mixtures containing CH4, D2, and Nz. Lapp, Goldman, and Penney (224B) observed laser Raman from flames; they obtained Raman data for Nz, 0 2 , and HzO vapor in Hz-Air and H2-02 flames. The resulting ground state and upper state vibrational levels showed great asymmetrical broadening. Searles and Djeu (307B) made gain measurements of the CO-P-Branch in a CzH2-02 flame. Benard, Benson, and Walker (32B) developed an NzO pure chemical cw flame laser. Veillon and Park (352B) described the direct analysis of mercury isotopes by atomic fluorescence spectroscopy. For elements with moderate mass and/or nuclear volume effects, as in Hg, and with pure isotope sources available, it was possible to measure the concentrations of the individual isotopes. Gawlik, Gawlik, and Kucal (135B) studied the forward scattering of resonance radiation by Na vapor in a magnetic field. 198R
Omenetto and Winefordner (271B)have given a systematic nomenclature for the types of atomic fluorescence transitions; the need for this nomenclature arose from the use of a laser excitation source which will excite more types of atomic fluorescence. R a t e Dependent Studies. Kelly and Padley (206B) measured collisional ionization cross-sections of gaseous metal atoms in Hz-02-inert gas flames of temperatures 2000-2800 OK by means of optical and electrostatic probe measurements; the cross-sections were between 10 and 145 nm2and showed no correlation with corresponding optical quenching cross-sections of the first excited states of M. Preist (287B) discussed semiquantitatively the ionization M* A+ + e M*’, where A is an atom process A and M* and M*’ are different excited states of a molecule; this mechanism is the major ionization process in flames. Hayhurst and Kittelson (153B) determined ionization potentials of CaOH (6.11 eV) and SrOH (5.69 eV) in H2-02-Nz atmospheric laminar flames having temperatures in the range of 2080-2570 OK; the ions were measured by mass spectrometry (155B). The most abundant ions for the alkaline earths were always found to be MOH+; mechanisms for their production were given. Nesterko and Taran (258B) studied the temperature deendence of the ion recombination coefficient in hydrocaron flames. Ashton and Hayhurst (16B)studied the kinetics of collisional ionization of alkali metals and recombination of electrons with alkali metal atoms in flames. Saito (301B) measured microwave reflection from the rear side of the detonation wave in an equimolar CzH2-02 mixture a t low pressure and determined the electron density and collision frequency at the reflection fronts; the ion-electron recombination rate constant was determined from the electron density and the dc probe current profile. Miller (245B), using flame ion mass spectrometry, microwave cavity resonance, an electrostatic probe, and absorption spectrometry, studied the formation of Cr-containing ions in fuel-rich atmospheric Hz-02-Nz flames seeded with K ; electron affinities of HCr03 (229 kJ/mole) and CrO3 (390 kJ/mole) were determined. Bradley, Jesch, and Sheppard (48B) gave a semitheoretical, quantitative treatment of the interrelationship between extra-equilibrium excitation of some species and elevation of electron temperature above the gas temperature in some hydrocarbon-air flames; it was found that the electron temperatures, via gaining of energy by electrons from reaction zone species in extra equilibrium excitation, could be elevated by some 100’s but not by 1000’s of degrees as a consequence of collisions of the second kind, possibly with vibrationally-warm OH. Bradley and Ibrahim (47B) correlated electrostatic probe theories and measurements in flame plasmas. Fowler and Priest (134B) measured ionization rates and cross-sections of alkali metals in atmospheric CO-OZ-N~ and Hz-OZ-N~ flames; the authors agreed with the Hollander model; namely, that ionization of the alkali metal occurred from a state near the ionization continuum by collision with an excited gas species, here nitrogen. Hayhurst and Telford (157B) measured the rate of ionization of alkali metal atoms in H2-02-N~ flames using a quadrupole mass spectrometer (155B) to determine the concentrations of the ionic species; the ionization cross-sections were found to be in the range 2.5 f 1.1 x 10-16 m2, and the excitation mechanism is assumed to involve the “ladder-climbing” model of Hollander. Several flame ionization studies, specifically performed to obtain a greater understanding of the flame ionization gas chromatographic detector, have direct application to flame spectrometry. These studies include: those by Blades (36B) concerning the mechanisms of ion formation, the equal per carbon response, the collection of ions, and the origin of carrier gas effects; by Blades (37B) concerning the response of the flame ionization detector to fluoro-alkanes; by Bolton and McWilliam (40B) concerning an analysis of the current shape from a flame ionization detector when used to detect the current due to burning spherical aerosol particles, and by Aue and Hill (19B) concerning the operation of a flame ionization gas chromatographic detector by reversing the gas flows and using it for metal detection, e . g . , ferrocene, tetraethyllead, and tetraethyltin. Blades (36B) reviewed the evi-
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dence for the C H - 0 mechanism and gave a special mechanism for nitriles; additional mechanisms were given which accounted for the ion formation from C2H2. Equal per carbon response was a result of complete conversion of the organic molecule to CH3 prior to entry into the oxidative zone. Ion-molecule reactions in flames previously published were of little use for the flames ionization detector. Bolton and McWilliam (40B)described the burning of an aerosol when controlled by inward diffusion of oxygen; the ionization produced by the burning changed the conductivity of the flame, and so there was a timedependence resistance. A differential equation for the current pulse was given; the expressions were general and applied to the burning of an aerosol when controlled by surface area. Dixon-Lewis and coworkers (107B, 112B, 113B) studied the structure of a rich H2-02-N2 flat flame a t 93 Torr, of rich H2-02-Nz flames a t atmospheric pressure, and of the overall reactions of heavy water, deuterium, and carbon dioxide added to some fuel-rich atmospheric H2-02-N2 flames. Burning velocities were measured and compared with values computed on the basis of a previously-given mechanism.' Rate constants for formation of the flame gas radicals were given. Cox, Jones, and Weinberg (94B) measured heat transfer from rotating arc augmented flames and plasma jets. The heat transfer coefficient was found to be directly proportional to tan 8, where % is the ratio of the swirl velocity to the axial velocity and was related to mass flow, temperature, and angular velocity of the gas but independent of temperature stratification and turbulence. The proportionality constant was constant for any gas but increased with increase of heat of reaction and dissociation. Chappell, Cooper, Smith, and Dillon (70B), using the methods of kinetic theory, described the radiational profiles of spectral lines emitted from atoms immersed in a gas of perturbing particles. Husain and coworkers (1B, 2B, 158B, 159B, 181B, 183B) used time-resolved atomic absorption spectrometry for kinetic studies of electronically-excited lead atoms (181B, 183B), for kinetic studies of electronically-excited oxygen atoms (158B, 159B). and for kinetic studies of electronically-excited phosphorous atoms ( I B , 2B). The atomic species were generated by pulsed photolytic initiation. Rate constants for collisional and quenching deactivation of the excited atomic species with various molecules, including inert gas atoms, C02, CO, H2, 0 2 , N2, NO, N20, CH4, CzH4, CZHZ,CFI, SF6, Pb(C2Hb)4, etc., are given. The results are discussed in terms of the effects of spin and orbital symmetry in the collision intermediate. Clyne and coworkers (31B, 80B, 81B) used atomic resonance fluorescence spectroscopy to determine the rate constants for rapid bimolecular reactions of 0 2 NO2, C1 + ClNO, and Br C1NO (80B) and for C1 BrC1, C1 Br2, C1 + IC1, Br IBr, and Br IC1 (81B) and to study the kinetics of formation and quenching of excited Br (31B). In the first two studies, rate constants for the designated reactions were given, and in the latter paper, quenching cross-sections for excited Br by He, Hz, N2, CO, SF6, and Brz were given. Horie and Frazier (172B) determined the rate of recombination of Br atoms with HBr as a third body in a steady, laminar, low pressure HZ-Br2 flame; a Br atom detector consisting of a pair of Ni-wire coils in a Wheatstone bridge was developed and combined with a microsampling method to determine the Br atom concentration. Schenck, Hilborn, and Metcalf (304B) studied time-resolved fluorescence from Ba and Ca excited by a pulsed tunable dye laser. The effect of NO on the recombination of H atoms in fuel-rich propane-OZ-Nz flames was studied by Smith (319B);the mechanism put forth by the author involved NO a molecular the formation of HNO from H species M, the reaction of HNO with H to give H2 and NO, and the reaction of HNO with OH to give HzO and NO. Rate constants were given. The kinetics of NO formation in propane air flames and in premixed Hz flames was studied by Shahed and Newhall (310B) and by Takagi, Fujii, and Ogasawara (336B) and Homer and Sutton (171B). Shahed and Newhall (310B) using spectroscopic methods measured the rate of formation of NO in high
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pressure combustion processes with propane-air and H2air mixtures; the results indicated that most of the NO formation occurred in the post-flame combustion gases. Takagi, Fujii, and Ogasawara (336B) determined the concentrations of CO and NO from a propane-air premixed flat burner flame, and they concluded that the formation and stabilization of NO in stoichiometric and fuel-lean flames could be predicted by two reactions: 0 + Nz = NO N; and N + 0 2 = NO 0. For fuel-rich flames, very rapid NO formation was observed in the reaction zone; these results could not be explained by the above reactions in the post reaction zone. Homer and Sutton (171B) obtained profiles of NO concentration in atmospheric pressure, premixed, H2-02-N2 flames with flame sampling and gave a mathematical model describing the chemistry of the burnt gas region. Results showed that most of the NO was formed early in the flame as a result of 0-atom concentration overshoot. Durie, Johnson, and Smith (118B) determined the mechanism of the S02-catalyzed recombination of excess H atoms in the burnt gas of isothermal propane-02-N2 flames at 2110 OK. Kallend (203B) also studied the effect of SO2 on the kinetics of radical recombination but for premixed fuel-rich H2-02-Nz flames (temperature range of 1600-2115 OK), both mechanisms involved an equilibrium in which HSOz was formed. Burdett and Hayhurst (6%) studied the kinetics of formation of chloride ions in C1-, atmospheric pressure flames via HC1 + e - = H rather than via slower three-body processes. Hayhurst and Telford (156B) determined the kinetics and heats of reactions of H H OH = H 3 0 + + e - in the reaction zone of hydrocarbon-containing flames (2000-2450 OK). The mechanism of production of electronically-excited BaO uia reaction of Ba 0 2 was studied by a diffusion flame technique by Obenauf, Hsu, and Palmer (265B). Pomart (285B) discussed the mechanism of combustion of a H2-02-N~ flame. Broadening of Spectral Lines. Wagenaar and DeGalan (355B) determined the atomic line profiles of 18 atomic transitions of 9 elements (Al, Ca, Cr, Ga, In, K, Mn, Mo, Ti) emitted by hollow cathode lamps and by a C2H2-N20 flame by means of a Fabry-Perot interferometer. The contribution of self-absorption to the profile widths was estimated and the appreciable influence of hyperfine structure to the profiles was considered. For 13 transitions having known hyperfine structure, the experimental curves were compared with computer-simulated spectra to calculate the collisional broadening of flame lines. Flame lines were significantly shifted to the red and collisional broadening in the flame was comparable with Doppler broadening a -0.5 to 1.5). Kirkbright and coworkers (9B, 210B, 211B) determined the absorption half widths for the 422.7-nm Ca line in Hz-NZ and H2-Ar diffusion flames using a continuum source and a piezo-electrically scanned Fabry-Perot interferometer (a 0.89-1.25 and collisional cross-sections -34 to 54 x 10-16 m2), the emission line widths for Ca 422.7 nm in CnHz-air and C?H2-N20 flames, with and without flame shielding, and inert gas separation using a Fabry-Perot interferometer, and corrected for self-absorption by extrapolating to zero added Ca (a -0.43-0 93 and collisional half widths -22-30 x m2), and the absorption line widths for Ca 422.7 nm in CzHz-air and C ~ H Z - N Z O with , and without flame shielding, using channeled spectra produced with a continuum source and with correction for self-absorption (a -0.46 in CzHz-air to 0.72 in CzHz-NzO and collisional half widths of 31-40 X m2). Kirkbright and coworkers (9B, 21OB, 211B) corrected for instrumental broadening as well as self-absorption in all studies. Veillon and Merchant (351B) described a stable, piezoelectrically scanning Fabry-Perot interferometer in conjunction with a conventional grating monochromator to obtain an overall spectral bandwidth of 0.0013 nm and a continuum source flame system for absorption measurements in the range 320-360 nm. Results for Cu and Ag indicated similar sensitivities as obtained with conventional line sources. Hannaford (147B) measured the hyperfine structure of Au hollow cathode lines by means of a conventional Fabry-Perot interferometric system. For Au 312.3- and
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479.3-nm lines, unresolved hyperfine structure contributed directly to the broadening of the measured profiles. For the Au 242.8- and 267.6-nm resonance lines, the presence of hyperfine structure effectively reduced the peak absorption coefficient which had the same effect as a large Doppler width. The large ejection velocities of the sputtered gold atoms did not contribute significantly to the emission Doppler widths a t the Ar-pressures normally used in hollow cathode lamps. Kielkopf (209B) described a new approximation to the Voigt function with application to spectral line profile analysis. Meredith (243B) also gave a new method for the direct measurement of spectral line strengths and widths which minimized the major errors in line profile studies; namely, the 100% transmittance uncertainty and instrumental broadening. By means of correction curves obtained from passing an idealized spectrometer slit function over assumed profiles, errors in the absorption profiles could be minimized. Ya'akobi (364B) showed that line broadening due to absorption of radiation was unlikely. Berman (34B) considered the speed dependence of the collisional width and line shift parameters and has derived an expression for the line profile accounting for the speed dependence. Tvorogov and Fomin (346B) considered the problem of the spectral line shape in the far wings of the absorption band. Hess (161B) considered the shape of well-resolved spectral lines for emission, absorption, and scattering phenomena in gases by a kinetic equation approach; a spectral function was derived which reduced to a Doppler profile and collisionally broadened Lorentzian line a t low and high densities, respectively; and which described Dicke narrowing at intermediate frequencies. Kucerovsky, Brannen, Rumbold, and Sargent (219B) used a Voigt profile to analyze the absorption spectrum of a gas measured with laser spectrometry; this paper was then criticized by May (239B), especially with regard to the validity of the Voigt profile application. Spectral Characteristics and Temperatures of Flames. Reif, Fassel, and Kniseley (293B) have given a critical review of the basic theoretical principles of temperature measurement of completely uniform flames by the line reversal, emission-absorption, slope, and two-line spectroscopic techniques. A major portion of the review concerns the extension of the basic theory to the temperatures of more realistic non-isothermal, non-homogeneous flames. The measured temperatures were shown to depend upon: (i) the measurement method employed; (ii) the energy of the quantum states involved in the line producing transition(s); (iii) the particular temperature gradient in the flame; (iv) the particular concentration gradient of the thermometric species. Measured flame temperatures did not represent either the average or the u'eighted average flame temperature but rather corresponded to an apparent temperature that described the ratio of the total number of species in the relevant quantum states measured by the spectrometer. Omenetto, Benetti, and Rossi (268B) described a unique means of flame temperature measurements based on atomic fluorescence of thallium with a continuum source of excitation. By measuring the ratio of fluorescence signals due to Stokes direct line fluorescence and anti-Stokes direct line fluorescence and by accounting for the relative efficiencies of the optical system and for the irradiance ratio of the source at the two excitation wavelengths, the flame temperature was calculated. The experimental results for CZHZ-N~O,CzHz-air, and H2-air flames agreed well with other spectroscopic methods of flame temperature measurement. Omenetto, Browner, Winefordner, Rossi, and Benetti (269B) described a color temperature atomic fluorescence method for flame temperature measurements; this work was based on the previous paper (268B). In this method, it was necessary only to measure the color temperature of the blackbody source and the same ratio of fluorescence signals described above to determine the flame temperature. The results of this method were found to be quite reliable as long as the intermediate level had an energy of 21 eV. Experimental results compared well with those obtained by the line reversal method for H2-02-Ar flames. Browner and Winefordner ( 5 4 B ) also described a method, similar to one de200R
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scribed earlier by L'vov, for determination of flame temperatures by measuring the ratio of absorption fractions of two lines of T1, In, or Ga or any other metal having spectral lines with different lower energy levels but similar wavelengths. A continuum source was used, and for the analytical flames of Hz-02-Ar, CzH2-air, and CZHZ-N~O, the In lines of 410.2 and 451.1 nm. The measured flame temperatures for the cooler flames agreed to within 20 "K of the line reversal values and for the hotter flame agreed to within 35 OK with the 2-line method. Bazakutsa and Sobolenko (29B)described the use of the line reversal method to measure flame temperatures of colored flames. Terao and Tatsumi (338B) briefly discussed a possible means of flame temperature determination using a laser. Babaev, Glazunov, and Tsys (21B) used a tunable laser to measure neutral gas temperature, vibrational level populations. and probabilities of transitions via the gain or absorption coefficients of individual vibrational-rotational levels of the various branches of the vibrational transitions in a molecular system. A COZ laser was used in these studies, and the pertinent equations were derived. Preobrazhenskii and Yudelevich (288B) described a pyrometric method for studying high temperature flames; this method was based on the application of Kirchhoffs law. Suckewer (331B) described the measurement of temperature by recording the absolute line emission intensity as a function of plasma optical thickness; the basic equation was derived and the experimental setup consisting of 2 mirrors was described. Usher and Campbell (348B) devloped a new method to determine the temperature profile of an optically-thin plasma; the method was an extension of the brightness-emissivity method. Numano (264B) compared the theoretical reversal temperatures determined by either narrow or broad slits; the temperatures obtained with broad slits were almost independent of the optical thickness of the gas. DeGroot and Jack (109B) compared the methods of Bartels and Kruithof for measuring plasma temperatures of selfabsorbed spectral lines. Bartels' method consisted of measuring the line emission of an inhomogeneous gas and for a rotationally symmetric plasma in local thermodynamic equilibrium; the radial temperature profile was found by measuring the spectral intensity maximum of a non-resonant self-reversed line. Kruithof's method consisted of measurement of both the emission and absorption in the wing of a spectral emission line and required more extensive handling of experimental data than the Bartels' method, but it did give more physical meaning. Wesselink, DeMooy, and VanGemert (359B) used a modified Bartels' method to determine the temperature of a high pressure optically-thick gas discharge. Greenwood (143B) described the types of errors resulting in the line reversal and Kurlbaum methods due t o reflection of gas radiation by the ribbon filament lamp. Mermet and Robin (2448) discussed the Abel inversion to obtain local flame temperatures; expressions for the Abel inversion and results were given. Kalff and Alkemade (201B) gave the characteristics (flame temperatures-2680-2860 OK-as determined by the line reversal method, concentrations of H and OH radicals as determined by the LiOH/Li method, burning velocities-30-75 cm/sec-as determined from the height of the combustion cones. the absolute intensities of the quasi-continuum emission of the burnt gases, and the electron concentrations-109-101'J cm- 3-measured with the HF resonance method) of premixed laminar atmospheric CO-NzO flames. Stephens (325B) designed an 02-shielded CzHz-air burner for analytical atomic absorption spectrometry and evaluated the characteristics of such a flame. The chemical-reducing properties and temperature were higher than for a CzHz-air flame but lower than for a CzHz-NzO flame. The burning velocity of the 02-shielded flame did not differ greatly from the C~Hz-airflame, and so the risk of flashback was not great. Also, the background was much less than the CzHz-NzO flame. The analytical sensitivity, however, was similar to the CzHz-air flame for several elements and significantly poorer than the CzH2-NzO flame for elements forming stable monoxides. Stephens and West (326B) also evaluated some low pres-
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sure flames for analytical purposes; these flames appeared to be of little analytical use despite their low backgrounds. Aldous, Browner, Clark, Dagnall, and West (5B) used Schlieren and shadow techniques to study flame processes. Shadowgrams were simpler to obtain and gave considerable information concerning optimal signals and signal noise in atomic absorption, emission, and fluorescence spectrometry. For example, the beneficial effect on the signal noise due to the use of a Nz-separation was evident from a shadowgram. Kogelschatz and Schneider (215B) used Schlieren methods to study high current, pulsed arcs and also described a new formalism for a n Abel inversion. Mossholder, Fassel, and Kniseley (251B) studied the spectrometric and analytical applications of premixed H2-02 flames. Fourteen elements were studied; despite the high maximum temperature of 2950 "K, the premixed H2-02 flame offered few advantages as a cell for atomic absorption spectrometry. The resulting atomic absorption limits of detection for the 14 elements were generally infe'rior to those obtained in C2H2-N20 and CZHz-air flames and serious solute vaporization interferences were observed in the relatively cool, very fuel-rich flame needed to obtain adequate atomization of elements forming stable monoxides. For several elements, emission limits of detection were similar to those obtained by the CzH2-NzO flame, and this was a result of the lower noise level in the premixed H2-02 flame. But for elements forming stable monoxides, the C ~ H Z - N ~flame O was superior in detection power to the premixed H2-02 flame. By assuming a thermodynamic model, the degrees of metal monoxide formation for Na, Fe, Be, and Ti were estimated. The flame was not recommended for future analytical studies. Chevaleyre, Matray, and Janin (76B) determined the theoretical maximum temperature of an HZS-FZ flame to be 3469 "K and obtained good experimental agreement via rotational temperatures of the 1-0 and 3-0 bands of HF. Chevaleyre and Janin (75B) also measured the temperatures of a diffusion flame of CH4-Fz by means of the 1-0 and 3-0 bands of the vibration rotation system of H F and the 0-1 band of the zZ-zZ+ system of CN. Chevaleyre and Janin (74B) made intensity measurements of the rotational lines of the 1-0 band of the H F vibration-rotation system to determine the temperature of a H2-F2 flame; good agreement with experimental values was obtained. Cros, Bouvier, and Chevaleyre (96B) measured the flame temperature of a CzNz-NO flame, obtaining a maximum measured temperature of 4750 "K. Zabryanskii and Grebenshchikov (368B) studied the temperature of combustion for hydrocarbons. Vovelle and Delbourgo (354B) made temperature and concentration profiles of flames of ethyl ether-air. Malet (235B) studied sodium flame temperatures to confirm the mechanisms suggested for the combustion model and for the formation of oxides for each flame type. Silla and Dougherty (313B) compared single- and double-probe measurements of electron temperatures in CO-02 flames containing either ethane or NaCl a t a pressure of 49 m m Hg; the single-probe measurements were found to be as reliable as the double probe ones. Fissan and Pfender (132B) described a modification of the cooled-radiation probe method which included a second probe for measurement of temperature and concentration distributions of combustion gases. Brule, Michaud, and Barassin (57B) used double-probe measurements of electron temperatures for low pressure diffusion flames and critically evaluated the method of determining the electron temperature from the double-probe current voltage characteristic. The volume between the probes was used for emission and absorption measurements. If the volume between the probes was small, homogeneous conditions could be assumed. The experimental results for a premixed Na-seeded propane-air flame showed that the system could be used for spectrometric temperature and concentration measurements. Bratzel and Chakrabarti (50B) used the Browner and Winefordner (54B) method of temperature measurement to determine the temperature of the atomic vapor produced by a non-flame carbon rod atomizer. With an Ar sheath gas, the highest gas temperature was 2770 "K for
Ga and 2080 OK for In, and so thermal equilibrium did not exist in the atomic vapor. Ashton and Hayhurst (I7B, I8B), with the point source technique for measuring gas phase diffusion coefficients, measured diffusion coefficients for NO (17B) and for Li, K, Rb, and Cs (18B) in Hz-02-Nz flames in the temperature range of 1920-2520 OK. The air afterglow emission was used to monitor the NO emission, and the atomic emission of the alkali metals was monitored. For NO and for the alkali metals, interacti'ons with principal flame species were accounted for with a Lennard-Jones function or a purely repulsive inverse power potential function (in the case of NO). West, Tassel, and Kniseley (360B) accounted for enhancements of refractory metal emission and absorption by a variety of concomitants in Ar shielded CzH2-NzO flames supported on slot burners by means of lateral diffusion of the analyte atoms, ions, and molecules. Thus, the analyte concentration actually increased at the flame center and decreased on the flame edges because of the presence of some concomitants. The proposed mechanism to explain the diffusion interference phenomenon was: the concomitant delayed the atomization of spray droplets or solid particles, thus shortening the time available for lateral diffusion in the flame by analyte species before they reached the observation zone; the analyte-free atoms or molecules were thus concentrated in the center of the flame and diluted a t the flame edges. Vander Hurk, Hollander, and Alkemade (349B) measured the ratio of band to atomic line emission for alkaline earth elements in 2 flames of the same temperature but different composition to determine the alkaline earth species existing in CZHz-air, CO-N2-02, CO-NzO, and Hz-air flames. In all of these flames, the Ca and Sr bands were due to the monohydroxide, whereas the Ba bands were due to both the monoxide and the monohydroxide. Singh and Mohan (314B, 315B) observed the molecular emission spectrum of BaF and CaF in a high temperature vacuum graphite furnace, and Monjazeb and Mohan (249B) observed the thermal emission spectra of CrS and MnS in a similar furnace. Becker and Schurgens (30B) measured the emission spectrum of Mo(CO)6 H and M O ( C O )+ ~ N atomic flames. Radziemski, Steinhaus, and Engleman (290B) determined high resolution atomic absorption spectra of uranium by the flash-photolysis and flash-discharge methods. Roux, Effanton, and D'Incan (298B) measured absolute R-line radiances in the 2-0, 3-1, 4-2, 5-3 vibration-rotation bands of CO with a high resolution IR grill spectrometer, a blackbody source, and a C2H2-02 flame. Comeford (86B) measured the spectral energy distribution from radiant sources used in standard tests of inflammability. Carstens, Brashear, Eslinger, and Gruen (67B) have written an extensive paper correlating gaseous atomic spectra and the absorption spectra of atoms isolated by noble gas matrices; a set of tables is given including the intensities of all experimentally observed gaseous absorption transitions involving the atomic ground state for 64 elements. Homann and MacLean (I70B) studied the CC12F2-F2 flame a t low pressure; they measured concentration profiles of species in the reaction zone by a molecular beam sampling method. Yarin (366B) studied the aerodynamics of laminar diffusion flames. Zaitsev and Tverdokhlebova (369B) studied the decomposition of a plasma in a CzHz-02 flame a t very low pressures. Murray and Sergeant (23%) examined for four stoichiometric values, the luminosity of propane-air flames enclosed in a furnace by measuring the CO, CO2, 0 2 , and hydrocarbon concentrations, the temperature, the total radiation, and the radiation in the 4.3-4.5 p m region as a function of height above the burner. The luminous radiation was spectral in nature. Bulewicz and Padley (62B) critically examined the flame chemistry of neutral S n in Hz-02-N2 flames in the temperature region of 1800-2500 OK. The predominant neutral species was SnO, although some SnOH existed. The dissociation energy of SnOH was found to be D o (Sn - OH) 5 355 mJ/mole, and the likely mechanism of formation of SnOH which involved catalysis of Sn by H and OH radical recombination was discussed. Dougherty, McEwan, and Phillips (114B) measured the intensities of emission bands of Con, NOz, and IO after the addition of NO, 12, CzNz, and LiBr to CO-02-N2
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flames. Addition of NO produces a large decrease in 0atom concentration. Measurement of resonance Li absorption indicated that LiO was the major Li-compound formed in 02-rich flames. Dissociation energies of NaOz and LiOz were estimated to be 234 and 222 kJ/mole, respectively. Mularz and Yuen (2528) determined the radiative properties (absorption cross-sections) of aluminum oxide particles a t high temperatures (1920-2610 "K). Bouriannes (41B) studied experimentally the combustion of A1 in OZ-Ar-Nz-air mixtures. Alkemade, Hooymayers, Lijnse, and Vierbergen (IOB) measured the Na and K emission noise power spectrum in a premixed H2-02-N2 flame and found low frequency noise peaks below 100 Hz and a minimum noise a t 3000 Hz . Hadeishi and McLaughlin (146B) developed a new type of atomic absorption spectrometer. in which trace mercury was measured, based on hyperfine structure lines in a magnetic field; the device could detect Hg at a level of 0.04 part per billion. Stirling and Westwood (327B) used atomic absorption spectroscopy to detect the atoms sputtered from Ni and Fe cathodes in glow discharges of Ar; the observed spatial distribution of sputtered atoms differed from that predicted by diffusion theory and indicated that some sputtered material was ejected from the cathode a s molecules or groups of atoms, and a relationship describing the deposition rate of sputtered atoms was given. Fazekas and Mezey (126B) measured the concentration of metal atoms in a metal atom beam by atomic absorption spectroscopy. Muradova and Muradova (254B) determined the absolute concentration of Zn atoms in the gas phase (571-717 "K) by atomic absorption spectroscopy. Harvey and Jessen (150B) used absorption spectroscopy to measure methyl radical, CH3, concentrations in low pressure CH4-02, &He-02, C3H8-02, C2H4-02, and CzHz-02 flames; the CH3 concentrations were similar in all the hydrocarbon flames studied. Jones and Padley (196B) used emission spectroscopy to determine CH3 and CH2 radicals in low pressure CzHz-02 flames; both of these radicals were formed in one-step processes via reaction of 0 and OH, respectively, with CzH2. Edwards and Balakrishnan (119B) used a non-gray, non-linear analysis of radiant heat transfer in a turbulent molecular gas to characterize the turbulence and radiation-molecular conduction ratio and optical depth. Rozlovskii (299B) has given an intensity relationship for a stationary flare above a burning liquid, and Triche (345B) has given a n expression for the intensity of emission as a function of temperature and atomic concentration for an explosive discharge. Laser Studies of Atoms. Omenetto and Winefordner (271B) have given a systematic nomenclature for atomic fluorescence transitions which is useful for describing laser excited fluorescence. Piepmeier (281B, 282B) in two fine articles derived rate equations to estimate the monochromatic laser power densities ( - 100 kW/cm2) needed to effectively saturate an excited atom population in typical flame gases (Z3000 "K) and to describe the influence of non-quenching collisions upon saturated resonance fluorescence. Piepmeier (281B) predicted a lack of sensitivity of fluorescence signal to variation of laser power output and to quenching. Also, Piepmeier (2828) predicted that non-quenching collisions which change the Doppler shift of a n excited atom would decrease the laser energy density needed to cause a given degree of saturation. Omenetto, Benetti, Hart, Winefordner, and Alkemade (267B) came to similar conclusions for a quasicontinuum laser source; they also predicted the independence of the fluorescence signal with laser intensity and with quenching collisions as long as near saturation was approached. Omenetto, Hart, Benetti, and Winefordner (270B) predicted the influence of source irradiance of high intensity as well as low intensity sources upon the shape of atomic fluorescence analytical curves; they showed that the range of linearity of analytical curves could be greatly extended a t the high concentrations of analyte with high intensity sources. Kuhl and Marowsky (220B) measured sodium concentrations down to 0.003 ng/cm3 using a tunable flashlamp pumped dye laser. Kuhl, Marowsky, Kunts202R
mann, and Schmidt (221B) described a simple and reliable flashlamp-pum ed tunable dye laser with spectral narrowing (to 0.005 spectral bandwidth) to increase the spectral irradiance of the dye laser by 2000 times. The laser was used to excite Na. Kuhl and Spitschan (222B) used a frequency doubled dye laser to excite the atomic fluorescence of Mg, Ni, and P b (limits of detection in a laminar premixed CzHz-air flame were 0.0003, 0.1, and 0.03 ppm); these workers observed saturation effects for Mg. Konjevic and Konjevic (216B) detected the absorption by 2 x 10-'3 g/ml of Na in natural gas-air flame by placing the flame in the cavity of a flashlamp-pumped dye laser. Trash, von Weyssenhoff, and Shirk (3438) have detected absorption from transient molecules, BaO, CuH, and HCO in CpHs-air flame placed in the cavity of a flashlamp-pumped dye laser. Keller, Zalewski, and Peterson (204B) have detected the absorption spectrum of Eu(N03)3 in a solution placed in the cavity of a flashlamp-pumped dye laser. Jennings and Keller (192B) have detected 2 pg/cm3 of Na by atomic fluorescence excited by a flashlamp-pumped tunable dye laser. Kishi and Okuda (212B) observed 2-'photon ionization of alkali metal vapors with a ruby laser. Isaev, Kazaryan, and Petrasch (187B) studied the properties and conditions for the occurrence of pulsed lasing of the T1-535.0 nm line in a T1 I vapor a t 370-390 OK; pulsed inversion of the T1 line occurred due to molecular dissociation by electron collisions resulting in population of the 72S1/2 level. Duong, Jacquinot, Liberman, Picque, Pinard, and Vialle (117B) observed the hyperfine splitting of the 2P1,2 and 'P3/2 states of Na by atomic absorption with a cw tunable dye laser. Johnson, Capelle, and Broida (200B) observed the laser excited atomic fluorescence and radiative lifetimes of A10, and Jackson (189B) observed the laser excited fluorescence of CN radicals. Penner, Sulzmann, and Chen (278B) used tunable laser derivative spectroscopy for spectral line profile measurements. Sulzmann, Lowder, and Penner (332B) have given estimates of detection limits for combustion intermediates and products with line center absorption and derivative spectroscopy using tunable dye lasers; detection limits 2-3 orders of magnitude smaller than by correlation spectroscopy were obtained. By irradiation with a ruby laser, either free-running or &-switched, Zhuravle, Zelikson, and Petrov (370B) observed the excitation of appreciable electrical signals in a free-burning alcohol-air flame. Buger, Sadie, and Malan (59B) investigated the light emission of a C2Hz-02 flame in the laser cavity; the stimulated emission in the fundamental band of CO was partially absorbed by the HzO found in the reaction resulting in low total output. Degiorgio and Lastovka (108B) have given a quantitative treatment of the statistical errors in intensity correlation spectroscopy, and McIlrath and Carlsten (242B) have given the equations of motion of the density matrix of a two-level atom in the presence of a n intense multimode radiation field of a multimode laser. General Interference Studies. Riandey (294B) reviewed some of the unsolved interference problems and mechanisms in flame spectrometry. Roos (296B) considered the releasing effect of "IC1 on Cr in a CzHZ-air flame; he suggested a mechanism proceeding uia a distillation, similar to the "carrier distillation" effect in arc emission. Kornblum and DeGalan (217B) investigated the influence of excess cesium upon the atomic line intensities or absorbances of 20 elements, with ionization potentials of ' 2 V , in a C2Hz-NzO flame; true degrees of ionization were derived from the intensity increase upon addition of Cs if corrections for incomplete atomization were made and if no molecular ions are formed. Bulewicz and Padley (61B) considered catalytic effects as possible interferences in flame spectrometry; they suggested that the interfering metal may act through catalysis of the recombination of excess free radical concentration leading to a significant change in the population of analyte tied up as compounds. Haraguichi, Shiraishi, and Fuwa (149B), using molecular absorption, studied the recombination reaction between In and C1 in a CzHz-air flame; the formation of InCl explained the interference of HC104 in the determination of In by atomic absorption spectrometry. Barsukov, Bukreev, and Grigor'ev (258, 26B) have given a theoretical calcula-
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tion to account for the interference of “ 0 3 on the intensity of emission of Na atoms in a flame. Thomas and Pickering (340B) discussed the role of solution equilibria in atomic absorption spectrometry with CzHz-air and CZHZ-NZO flames; the elements studied included Ta, Nb, Ti, Y, V, W, and Ni and species shown to influence the atomic absorption results included HF, H3P04, HzS04, Ca2+, K + , Ala+, Fe, Mn, and EDTA and ammonium acetate. Analytical Figures of Merit. Averbukh and Yagnyatinskaya (20B) studied factors limiting sensitivity of atomic absorption spectrometry, including non-selective absorption and light scattering by particles and inhomogeneities in the flame. Yudelevich, Shelpakova, Brusentsev, and Zayakina (367B) applied the analysis of variance to chemicospectrographic, flame emission, and atomic absorption spectrometry for the analysis of trace impurities in order to assess the reliability of the procedures. Erkovich, Raikhbaum, and Malykh (121B) discussed the factors affecting accuracy and sensitivity (analytical curve slope) in the atomic absorption analysis of solutions; the most important factors being gas rise velocity and solution flow rate. Fal’kova, Livshits, Slavn’yi, and Bol’shakova (123B) discussed the accuracy of semiquantitative spectral analysis and the means of grouping results to obtain estimates of the errors. H. Kaiser (200’B) has given an excellent account of the definitions of selectivity, specificity, and sensitivity of multicomponent analytical methods. Watts (357B) discussed some of the systematic errors in atomic and molecular absorption spectrometry. Guzeev, Naiorov, and Nedier (145B) compared theoretical detection limits of atomic absorption and atomic fluorescence methods. Parsons and McElfresh (277B) also compared theoretical and experimental detection limits in atomic absorption spectrometry with the CzHz-air and CzHz-NzO flames; relatively good agreement between theory and experiment was found. Roos (297B) expressed the variation in standard deviation with transmittance for a large number of elements in terms of four-component error functions, each one characteristic of one (or more) possible source of noise associated with measurement of transmittance (or absorbance). The major noise component in all cases was related to the dynamic nature of the flame. The smallest relative error, for most elements, occurred a t an absorbance between -0.35 and -0.61. Broekaert (52B) calculated detection limits in spectrographic analysis. Currie (97B) has written a fine article on the limit of precision in nuclear and analytical chemistry which is applicable to flame spectrometry. He proved that the precision is not indefinitely improved as the signal level was increased if additional sources of random error, other than counting error, were important. Some other studies of possible interest to flame spectroscopists include: the accurate determination of absorption line frequencies using simple least square convolution techniques by Johnson and Harmony ( I 9 9 B ) ;the error in absorption measurements caused by the presence of nonmonochromatic light by Agterdenbos and Vink ( 3 B ) ;the estimation of precision for the method of standard additions by Larsen, Hartmann, and Wagner (225B);the calculation of a complex chemical equilibrium in an ideal gaseous system by Vonka and Holub (353B); the use of a sophisticated desk calculator for construction of atomic absorption analytical curves and estimation of unknown concentrations by Butler, Jackson, and Kroger (65B);and the use of ratio matching, a statistical aid for discovering generic relationships between samples. High Frequency Sources of Excitation. Browner, Patel, Glenn, Rietta, and Winefordner (53B) described a novel means of increasing the intensity and stability of electrodeless discharge lamps (EDLs) operated a t microwave frequencies; the device consisted of simply thermostating the EDL by flowing heated air. The coupling device was an A-antenna. Ball (22B) has described convective heating of EDLs in a y4-wave cavity. Alger, Dagnall, Silvester, and West (8B) described a switched resistor modulation of EDLs. Dagnall and Silvester (IOIB) evaluated an attenuator between the magnetron and cavity t o increase EDL intensity stability. Dagnall, Silvester, and West (103B) also used electronic modulation of EDLs; the optimal frequency of modulation was a 20-kHz square wave, and modulation was achieved
by adding the modulation waveform to the reference of the stabilizing element in the microwave power supply. Schrenk, Valente, and Smith (305B)used a special tuning stub system for optimal operation of microwave-excited EDLs; the stub arrangement was used to balance load impedance with the output impedance of the microwave generator and the characteristic impedance of the coaxial cable. Kikuchi (208B) described a 35-GHz vacuum UV/ EDL, and Den Besten and Tracy (11IB) described a simple Ftf-excited EDL system. Gleason and Pertel (137B) gave a detailed procedure for preparation of EDLs to obtain long-lived, stable lamps. Brandenberger (49B) gave circuit details on a regulated microwave power supply for operating EDLs; simple circuits were used to improve line regulation and filtering. Smith (318B) described an improved microwave power source for EDLs; stabilization of light output rather than just magnetron output was achieved and a controllable modulator system was also described which allowed all modes of operation from cw to variable level pulse modulation to be applied to the microwave energy fed to the EDL. Phillips (280B) has described a means of modulation of EDLs a t frequencies of the order of 100 kHz. Stanley (323B) discussed a simple means of igniting EDLs with a photographic flashgun. Cooke, Dagnall, and West (88B) have considered line broadening in microwave excited EDLs for the more volatile elements of P, S, I, Se, Zn, Cd, and Hg and also discussed the beneficial and detrimental effects of line broadening in atomic absorption and atomic fluorescence measurements. Dagnall, Silvester, and West (102B) have given five new methods of preparation of EDLs of alkali and alkaline earth metals; the most successful method involved a discharge in flowing Ar a t 1 atm-a small amount of the element or its halide being suspended in the discharge stream. Unfortunately such a “flowing” source is short-lived, but it could be recharged readily. Microwave excitation of hollow cathode lamps was not found to be beneficial. Clack and Stanley (78B) described a reliable means of preparing alkali spectral lamps. Browner and Winefordner (56B) have carried out an extensive study of the optimization of EDLs for analytical atomic spectrometry. These workers indicated the need for temperature control of microwave excited EDLs and the advantages of the A-antenna over the Y4- and Y4-wave cavities as coupling devices for atomic absorption and atomic fluorescence studies. They also showed that the skin effect as well as a homogeneous plasma was present in EDLs, and that the probable mechanism of excitation was uia electron collisions. Busch and Vickers (64B) also performed measurements of spectral properties from a low pressure microwave excited Ar plasma, and they felt the excitation process was controlled by the concentration and energy of electrons in the high energy group, the concentration and energy of electrons in the low energy group, and the concentration of metastable Ar. Chakrabarti, Hoffman, Lichtin, and Sachs (69B) observed the 388.4-nm emission of binary mixtures containing Hg vapor and various other gases as He, Ne, Ar, Xe, Kr, Hz, CO, Nz, and CH4. Boggs, Sheppard, and Clark (60B) considered the effects of 2450-MHz microwave energy on human blood coagulation processes. No significant changes in platelet count, coagulation time, or clot strength occurred with microwave power densities up to 380 mW/cm2 for exposure times as long as 24 hr. Stanley, Bentley, and Denton (324B) studied the microwave radiation levels from the C-antenna, the tapered cavity, and the Evenson cavity; they observed radiation levels exceeding the present national safety standards. The reflection of microwave from or concentration of microwaves a t surfaces could cause excessively high energy levels. Thus, antennas and cavities should be properly shielded and checked for radiation levels. Hollow Cathode Lamps. Cordos and Malmstadt (89B, 91B) described a programmable power supply circuit for operation of hollow cathode lamps (HCL) in an intermittent current-regulated high intensity mode ( 8 9 8 ) and the characteristics of HCLs operated in this manner (91B). The output radiance was 140-200 times greater during the on-time than the maximal radiance in the dc mode, and the short- and long-term drifts are typically 0.08% and
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less than 0.27’0, respectively. The lamps had long lifetimes when operated in the intermittent mode. Holder, Lim, Maddux, and Hieftje (166B) have given a circuit to electronically-modulate the HCL current; the system increased reliability and resulted in a n adjustable degree of modulation, a greater frequency range, and the possibility of different modulation waveforms a s compared to mechanical choppers. Lloyd and Lowe (230B) described a gating technique for selective modulation of resonance lines from HCLs, by incorporating the gating within a synchronous detection system rather than using a switching device prior to amplification; unwanted signals were removed without the introduction of extraneous signals by the gating device. Dowd (116B) described a programmable power supply (up to 100 mA a t 400 V) for operation of HCLs. Berezin and Sten’gach (33B) described a spectral method of measuring the residence time of atoms in a hollow cathode; the residence time of atoms in hollow cathodes was about 2 msec which was about 10 times greater than the residence time of atoms in arcs. Witting (362B) measured electrical and optical characteristics of a dc hollow cathode with indirectly heated thermionic cathodes in Ar a t a few Torr. Van der Sijde (350B) measured the temperatures of atoms, ions, and electrons for a low pressure, magnetically-confined, hollow cathode Ar arc discharge in the 10-80 A region; population densities of the excited levels were mainly determined by the excitation cross-section functions for the levels concerned. Boshnyak, Zhiglinskii, Kund, and Khlopina (42B) investigated the electrical and optical characteristics of a discharge in a cooled hollow cathode. Novikov (263B) discussed the possibility of controlling the hollow cathode effect and extending its operating pressure to lower pressures by using a direct ionization source. Gorbunova and Semenova (139B) considered the intake and radiation of atoms in a hot hollow cathode discharge; atom-atom collisions play a major role in populating close-lying energy levels in non-equilibrium discharges. Gorbunova (138B) also studied the effects of metals and their compounds on the current-voltage characteristics in an uncooled hollow cathode discharge; an increase in propagation of metal powder (in the cathode) near its melting point always resulted in an increase in intensity of emission and a decrease in discharge electrical conductivity. Carstens, Kozlowski, and Gruen (68B) described a versatile hollow cathode source of atoms or molecules for matrix isolation studies of high temperature species; a dc discharge within the hollow cathode, sustained by flowing noble gas, sputtered atoms of the cathode metal from the surface producing a dilute mixture which was deposited a t low temperatures for subsequent absorption studies. Semenova, Kukhanova, and Tedorovich (308B) studied the increase in intensities of atomic lines due to the effects of resonance and recombination processes of Cu, Ag, and Au vapors in a high current (0.05-1.2 A) hollow cathode discharge. Rudnevskii, Maksimov, Shabanova, and Lazareva (300B) and Sen, Das, and Gupta (309B) studied the effects of magnetic fields on hollow cathode discharges; whatever the direction of the magnetic field with respect to the axis of the hollow cathode, a slight increase in emission intensity resulted as the magnetic field increased. Pacheva and Zhechev (274B) also studied the effect of a magnetic field upon a hollow cathode discharge. Mark, Lindinger, Howorka, Egger, Varney, and Pahl (238B) described a simple bakeable hollow cathode device for exploring the negative glow plasma. Mark (237B) studied by mass spectrometry the neutral species in the negative glow of a cylindrical hollow cathode discharge in Nz. Howorka, Lindinger, and Pahl (177B) used an ion sampling technique to study the ion content in the negative glow plasma of a cylindrical hollow cathode. Smith and Plumb (317B) appraised the use of a single Langmuir probe for the study of afterglow plasmas. Naoulo and Pham-Tu-Manh (257B) studied dense columns in hollow cathode discharges. Lorente Arcas (232B) developed a model for the hollow cathode discharge to explain the observed over-pressure phenomenon as being due to an electron pressure. Detection Devices. Jonas and Alon (195B) investigated the voltage dependence of the signal-to-noise ratio, SNR, a t low light intensities for the box-and-grid and venetian204R
blind type of photomultipliers used for both photon counting and dc modes of detection. The SNR was quite constant for both tube types with dc detection for increasing voltages, but with photon counting and the box-andgrid photomultiplier, SNR improved with increasing voltage. Santini (302B) and Ingle and Crouch (186B) exchanged some comments on the signal-to-noise ratio characteristics of photomultipliers and photodiode detection systems. The basis of the exchange concerned the relative merits of the two systems. Hamstra and Wendland (148B) measured the noise and frequency response (0.1-10000 Hz) of a silicon photodiode-operational amplifier combination; photodiodes operated photovoltaically were free of l/f noise in the dark and had a n optimum bias for maximal SNR. Keyes and Kingston (207B) have written a fine review on photon detectors. Barbanel (24B) discussed signal detection and discrimination in the presence of several classes of non-additive noise for analog image processing. Thiry (339B) evaluated the cathode quantum efficiency of several photomultipliers and photographic emulsions using a He-Ne laser. Birenbaum and Scar1 (35B) evaluated the cathode quantum efficiency (5.5%) and the photon counting efficiency (3.3%) of a n RCA-C3100F photomultiplier. Robinson, Williams, and Lewis (295B) evaluated the cathode quantum efficiency of an RCA-C3100E photomultiplier (7% a t 600 nm) by using a n incident light method. Budde and Kelly (58B) measured the variations in spectral sensitivity of the RCA-6217 and RCA-5819 photomultipliers a t low temperatures. The non-linear response of photomultipliers was studied by Sauerbrey (303B);non-linearities were caused by space charges between the cathode and first dynode and between the final dynodes. By avoiding fatigue by pulsed operation, the range of linearity extended as compared to d c operation. Sloman (316B) and Land (223B) exchanged comments on the region of linear operation of photomultipliers. Fenster, LeBlanc, Taylor, and Johns (128B) studied the linearity and fatigue in photomultipliers; when linearity was not achieved, a simple method could be applied to correct for the non-linearity. Davies (106B) discussed a method for reduction of dark current in uncooled photomultipliers; by using scrupulous care and making all connections to the pins of the photomultiplier and encapsulating the base in a silicone rubber potting compound, the dark current can often be reduced by lO3--i.e., often more than in a normally-operated, but cooled, photomultiplier. Shardamand (311B) described a compact photomultiplier housing which was cooled by flowing liquid nitrogen cooled helium through a series of coils which envelop the photocathode portion of the tube. Ellison and Wilkinson (120B) described the operation of a 1P28 photomultiplier a t high currents (up to 50 mA). Shaw, Grant, and Gunter (312B) described a total reflection system to provide optical enhancement of commercial photomultiplier tubes. Oh’bayashi (266B) studied the autocorrelation of dark pulses of the R374, R524, and R649 photomultipliers of the Hamamatsu TV Co., Ltd. Collins (231B) described a circuit which provided a suitable variable phase 100 Hz reference signal for a lock-in amplifier when a calibration source is used. Boumans, Rumphorst, Willemsen, and DeBoer ( 4 4 B ) have tested planar silicon photodiode arrays as detection devices for multichannel emission spectrometry. The noise level was completely determined by the preamplifier used. A linear response over 3 orders of magnitude resulted and a spectral resolution equivalent to that obtained with a scanning spectrometer with a photomultiplier resulted. The most serious disadvantage and greatest limitation to use of these devices for emission spectrometry was the significantly poorer (100-500 times) SNR than for photomultipliers. Boumans and Brouwer (43B) also described a one-dimensional array of 20 phototransistors as a device to measure intensities of closely-spaced spectral lines on the focal plane of a spectrometer; the system was used to detect 0.1 ppm of Ba in the presence of 2000 ppm of Ca by flame emission spectrometry. Horlick and Codding (175B) described the characteristics and uses of a commercial self-scanning linear silicon photodiode array as a spectral detector; the array consisted of 256 photodiodes per 0.25 inch. The diode array coupled to a spectrometer should allow such operations as time-averaging of repetitive
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Table I. Applications of Flame Atomic Emission Matrix
Element
Flame
Other comments
CIH,/N?O
Geological materia 1s P b metal Ceramics Blood serum Alkali metals
C2Hi,air C3H8/air H,/N*O CzH,/air
Na, Ca K K
Yttrium oxide Wine Dil. HF
C2H2,/air
Rb, Cs
Geological materials Granites I n presence of Ca Zr and ZiIcaloy-2 Rocks, minerals & biochemicals Complex niobates I n presence of PO,J-, so
