7
V O L U M E 2 3 , NO. 1, J A N U A R Y 1 9 5 1
T.I., and O r l o ~ a T. , Y . , Zaoodskayo Lab.. 15, 1365 (1949). (207) Veksler, R. I., Zhur. A n a l . Khim., 4, 14 (1949). (208) Veksler. R. I., Ibid., 5 , 32 (1950). (209) Vredenburg, R. M., and Ssckter, E. A , , C ~ LChem. Process Ind., 34, 119 11950). (210) Weissberger, -4., “Physical Methods of Organic Chemistry,” T’ol. I, Chaps. XXI, S S I I , Ten. York. Interscience Puh(200) Usatenko,
lishers, 1950.
(211) Welch Scientific Co., pamphlet, 1950. (212) Wiliar, H. H., and Wooten, A. L., ANIL. CHEM.,22, 670 (1950). (213) Window, E. H., and Liebhafsky, H. A , , Ibid., 21, 1338 (1949). (214) Wokes, F., and Slaughter, G., A n a l y s t , 74, 624 (1949). (215) Wollish, E. G., et nl.. ai^.^^. CHEM.,21, 1412 (1949). (216) Wrightson, F. M., Ibid.,21, 1543 (1949). (217) Zaichikova, L. B., Zooorlsbnyn Lub.. 15. 1025 11949). RECEIVED September 30, 1930.
Infrared Spectroscopy ROBERT C . GORE Stamford Research Laboratories, American Cyanamid Co., S t a m f o r d , Conn.
D
U R I F G 1950thegeneral trends in infrared spectroscopy have been similar t o those reported in the review for 1949 (120). From the spectra given in the chemical journals it appears as if a growing number of chemists are utilizing the information obtainable from them. With this wide dispersion of published spectra the need for a compound index is becoming more acute. Papers on instrument design were about the same in number as heretofore, with perhaps a slight upsurge because of the renewed interest in the spectral interval between 0.8 and 2.5 microns. Several excellent empirical qualitative studies on specific classes of compounds appeared, along with a new edition of Colthup’s useful spectra-structure correlations chart (70). Over 12,000 copies of this chart have been distributed to interested perqons. Papers on quantitative analyses of specific compounds comprise about 5,8a/, of all papers included in this review. Fundamental vibrational analyses of simpler molecules continued to be a field of major activity. Two important symposia were held. T h e one a t Ohio State University included over fifty papers on several phases of infrared spectroscopy. T h e first general discussion since 1945 of the Faraday Society on Spectroscopy and BIolecular structure, held a t the University of Cambridge, included twenty-four infrared papers. Problems in the cataloging of spectra and the use of punch card systems have received considerable attention. The general topic was discussed by Hallett (131), with specific systems described by Clark ( 6 1 ) and Shreve (285). A committee appointed at the Ohio State Symposium, headed by E. C. Creita of the Sational Bureau of Standards, has studied such systems in detail. Brode (44)has discussed nomenclature and presentation of abaorption spectra data in general. Several reviews on infrared spectroscopy appeared during the year, most of them in publications outside of the United States (37,155, 255,301,303). Coggeshall included infrared methods in 3 general review on determination of organic structure (65). BOOKS
No books devoted exclusively to infrared spectroscopy were published in 1950, but infrared chapters were included in several of the compiled books and general works on spectroscopy. In this latter group are books by Candler on “Practical Spectroscopy” ( 6 2 ) )by Johnson on “Introduction t o Molecular Spectra” (147), and by Pearse and Gaydon on “The Identification of 3Iolecular Spectra” (237). Herzberg has completely revised his classical work on “Molecular Spectra and hlolecular Structure, Volume I, Spectra of Diatomic Molecules” (137). Chapters on infrared spectroscopy in the compiled books were written by Coggeshall in Farkas’ “Physical Chemistry of Hydrocarbons,” Volume I (106); b y Jones and Dobriner in Harris and Thimann’s “Vitamins and Hormones,” Volume VI1 (132, 157); by Nielsen and Oetjen in Berl’s “Physical IIethods in Chemical Analysis,”
Volume I (25, 226); and by Brady in llellon’s “.%nalytical .It)sorption Spectroscopy” (212) INSTRUMENTATIOY
The year has seen another manufacturer of spectrometers, Grubb-Parsons in Fewcastlc-on-Tyne, announce the production of a percentage transmittance recording spectrophotometer This instrument can be made conveniently from the single-beam instrument by the substitution for the source section of a unit which includes the recorder. The Perkin-Elmer Model 21 doublebeam instrument has been described (190, 339) and its performance reported (336, 338). Several individual builders of spectrometers have described instruments with novel features. Bigay (30) reports the construction of a large aperture spectrometer useful in the ultraviolet and infrared. Bulloclr and Silverman ( 4 8 ) described a rapid scanning instrument with oscillographic presentation in the near infrared. Chapman and Torley (54)have constructed a mobile spectrometer which can be taken to the problem rather than having the problem come to it. Elliott et nl. described a lead selenide cell spectrometer (9‘7). Hales (129) tells of the installation of a double-beam instrument using a photocell amplifier. Hornig (142) has built a double-beam prism instrument with a servo slit control instead of cams. Savitzky and Halford (268) describe a double-beam instrument using phase discrimination rather than the usual attenuation of the reference beam. This latter principle is reviewed in an article by Schoen (269). Shurcliff (287)mentions a multislit double monochromator using no moving parts. An electronically determined double-beam instrument is described by Ganz and co-workers (353) Radiation sources are discussed by several authors ( $ 5 , 100, 649, 665). Prism materials are the subject of several papers. Davies (80) calls attention to the advantages of the synthetic silica over lithium fluoride in the near infrared up to 2800 cm - 1 Leconite (184, 185)has compared several prism materials, including some optical glasses. Plyler and co-workers (311, 312) have measured the refractive indexes of thallium bromide-iodide and silver chloride. Greig (123) describes a new mounting for an echelette grating. Radiation detectors and thermopiles are discussed by two authors (103, 139), while the absorptivity of certain metals is reported by another (335). >lathis et al. (204)report on the application of the lead sulfide cell to infrared spectrography. T h e infrared image converter and its use are the subject of four papers (11,13, 133,134). Infrared sensitive phosphors are discussed in three papers (12, 41, 79), while the theory of photoconductivity in infrared semiconducting films is reviewed by Ritter (666). Instrumental theory papers include the following: slit width effects (89), comatic aberration (93), slit dimensions and intensity (115),and the influence of resolution on band shape and intensity (243). Cells may be waterproofed by selenium films ( 6 ) , their thickness may be measured by a Rayleigh interferometer ( I $ 6 ) ,and they may be constructed to withstand 35 pounds per
8
ANALYTICAL CHEMISTRY
square inch (293). A sanitary seal for microcells has been devised ( 9 4 ) and a simple variable space cell constructed (337). The interesting optical properties of silicon and germanium have been discussed further in four papers (42, 43, 101, 177). Two papers offer aid In the troublesome job of calibrating prism spectrometers (%54,S20). Infrared microspectroscopy (with reflecting microscopical attachments) has been discussed by Blout ( 3 4 ) , Loofbourow (192),Mellors (213), and Wood (547). Double-beam gas analyzers for industrial use are examined by Kivenson (167). Filters for the infrared region have been described by Billings (31) and Blout (36). Polarization studies are being used by many workers as an aid in vibrational analyses and crystal structure determination. There were, however, a number of specific papers dealing with polarization (17, 164, 173). Walsh (332) and Rank ($61) have written papers dealing wholly with infrared absorption spectra a t low temperatures, although many of the workers reporting in the theoretical and molecular spectra section have utilized low temperature conditions. QUALITATIVE ANALYSIS
The papers listed in this section may or may not be extensive studies in qualitative analysis. True qualitative work, perhaps, includes the study of series of related compounds (such as sulfones) in order to fix empirically the frequency limits of absorption of the group under examination. Also listed here as qualitative work are those papers reporting infrared spectral studies which might be of aid to other spectroscopists in qualitative analysis. When reasonable attempts have been made to assign all frequencies, the papers are included in the theoretical and molecular section, although they may he of qualitative interest. Qualitative studies were made on the following classes of compounds or molecules: azobenzene (cis and trans) (306),benzene hexachloride ( 174), butenes and butadiene ( 7 6 ) , n-butyl group (sgo),calciferol (324),calcite (194) calcium oxide (144),calcium tartrates (183), carbohydrates (171 ), chloropentafluoroethane (16, 809), chloroethylene ( 2 9 ) , cinerolone ( 7 7 ) ) cinnamic acids ( 1 2 7 ) , clay (1), colchicine, (271 ), cotton powder (108), cresols (58,59),deuteronitrophenol (143), diamond (33))dibenzoylethylenes (172), dicarboxylic acids (295), ergostenyl side chain (166), epoxy group ( f o b ) ,esters of phosphorus oxy acids (214), ethyl acetoacetate (186), ethylene derivatives ( 1 4 , 808),fats and oils (32, 86), glasses ( 5 , 106), halogenated paraffins ( 5 6 ) ,hexabromocyclohexane (178), hydrocarbons (revien ) ( 1 6 ) , leaf alcohol ( 7 6 ) , magnesium oxide (341, 342), metallic trichloroacrylates (87), molecular complexes of diphenyl (51), neofatty acid (894), nitrous oxide (815), organic glasses (364),the 0-0 bond (181 ), parathion (92), penicillic acid ( l o r ) , penicillin (265, 328), propsrgylic alcohols and bromides (349), purines and pyrimidines ( 3 6 ) , &quartz ( 2 6 7 ) )reaction product of ethanolamine and arosilica matic aldehydes ( 7 8 ) ,retene (176),rubber (butadiene) (85), minerals (165), sulfur compounds (19, 279), terpenes (18, 846), 2-thio-oxazolidone (99), uranyl salts ( 2 7 3 ) . and vapors adsorbed on silica gel (175, 362). QUANTITATIVE ANALYSIS
The general papers in this field include one on the rapid calculation of multicomponent mixtures with punched card machines (233) and a discourse on the ratio method of analysis in spectrophotometric problems (239). This latter is primarily a visible spectroscopy paper but somewhat applicable to the infrared region. Sipple (g89) has given a derivation of the LambertBeer law on a geometrical and mathematical basis. The following specific quantitative analyses were reported: aspirin (with phenacetin, caffeine, and thenylene hydrochloride), (333,334), cinchonidine (with cinchonine, quinidine, and quinine) (a@), deuterium oxide in water ( S f O ) , the cresols (168),estradiol
( 5 3 ) , hexachlorocyclohexanes ( 179, 241 ), hydrocarbons ( 188, dsd), C1-G hydrocarbons (2961, naphtha fractions (M),octa-decanoic acids, esters, and alcohols (I84297), tert-butyl phenol8 (188), phenols, cresols, xylenols, and ethyl phenols (111), water in gaseous propane ( f l a ) ,and water in Freon-12 (24). HYDROGEN BONDING
Interest iri the spectroscopic manifestations of hydrogen bonding appears to have increased during the year. Coggeshall has written two interesting and timely papers dealing with the subject (66, 67). Batuev (IO) has proposed a “frequency-modulation theory” of the changes found in the spectrum on bonding. He also has estimated the potential barrier to proton transfer in systems (21). Ketelaar has discussed the energetics of the linkage (166). Other general papers include those by Freymann (110) and Gross (124). Studies on specific cases of bonding include that found in carboxylic acids ( 6 7 ) ,high polymers ( 6 2 ) ,phenol (195), chelate compounds (203),cellulose (24?),hindered phenols (278), and sulfur compounds (19). BIOLOGICAL
Many papers of biological interest are to be found in other sections of this review, for it is difficult t o have strict rules of classification. The two classes of compound studied most frequently during the year are those related to cancer and to proteins. In the first class are papers on the detection of ethylenic double bonds in steroids (166, 169, 160), keto steroids, and steroid esters (167, 158), polynuclear hydrocarbons (234), derivatives of stilbene (309), and a-tocopheryl hydroquinone (264). The papers related to protein structure include amino acids (180), the peptide link (187), synthetic polypeptides ( 9 5 ) , proteins (219), agenized protein (284), and insulin (96). POLYMERS
Bryant et al. (46) discussed polymerized nuclear-methylated styrenes, Ellis (114)near infrared pleochroism in polyvinyl alcohol, and Nochel (220) spectral changes with crystallization in neoprene. RE4CTIONS AND COMBUSTIO\
A relation between characteristic frequency and chemical reactivity was proposed by Anantakrishnan (4). Silverman et al. ( 4 7 )reported on infrared emission from carbon monoxide-oxygen explosions. Duchesne (84)has discussed the role of molecular vibrations in chemical reactivity, while Rolfhard and Parker (346) describe a new technique for spectroscopic examination of flames at normal pressures. ASTROPHYSICAL
These papers include studies on heavy water (HDO) in the solar spectrum (56), carbon dioxide (117, 119, 149), new solar lines (118, 197), solar spectroscopy with a Cashman cell (198), nitrous oxide (199), OH emission bands ( d f O ) , the polar aurora ( % # I ) , water vapor (250),the emission of the night sky (263),and an improved map of the solar spectrum between 9 and log ( 2 7 4 ) . INDUCED HOMOPOL4R ABSORPTION
During the year considerable interest has been aroused by the discovery that homopolar diatomic molecules may be made t o absorb in the infrared region. Papers discussing this phenomenon caused by condensation or pressure may be of interest (74, 163, 217, 290, 325, 348). ABSORPTIOh INTEh SITIES
This classification has been included in this review because of the increasing interest in the measurement of intensities useful in
V O L U M E 23, NO. 1, J A N U A R Y I951 the study of bond electric moments. Papers dealing primarily with intensity measurements include the following: the C-H link (69), theory ( 73),hydrocarbons (109), carbon dioxide (161),preseure broadening effects (169, 207, 326), cyanogen and cyanogen chloride (%SO), benzene (286), ozone (844), and water vapor (350, 351). A review summarizing some of the theory was written by Vincent (827). THEORETICAL AND MOLECULAR
These papers are again divided into two classes. The first, the theoretical class, contains the more general papers, while the second, the molecular class, contains papers dealing primarily with specific molecules. There is necessarily some overlapping of the two classes. The theoretical papers include studies on crystals (40, 81, 98, 141), rotation in the solid state (SQ),the angle-angle interaction in pyriniidal molecules (50), the validity and application of the molecular orbital method (71 ), complete sets and redundancies in vibrational Coordinates ( 8 2 ) , characteristic vibrations (121), calculation of refractive index from absorption data ( f a $ ) , energy levels and thermodynamic properties of the internal rotator (fSO), the plane symmetrical XZYzXz molecule (136),bond energies and bond lengths (191), reflection and transmission formulas for a film on a backing plate (206),axially symmetric molecules (225), emission from diatomic gases (258),the methyl mass in determining force constants (275), bond energy, dissociation energy, and the force constant (SOO), the force constant matrix (S05), developments in the theory of secular equations ( S f S ) , valence force coordinates in systems with nonideal angles ( S 1 5 ) , moments of inertia in molecules with internal rotation ( S I @ , the cubic secular equation (818 ) , oscillator contributions to thermodynamic functions (Sf 9 ) , general valence-force displacement coordinates (321 ), and the determination of thermodynamic data (531 ). The molecular studies on individual molecules include papers on the follorving: hydrogen sulfide ( 2 , 9,231 ), hydrogen persulfide (343),diborane (7), substituted ethanes (64, 170,218, 221, 229, 8882, 698), ethylene ( 8 ) ,halogenated and substituted ethylene (26, 827, 228, 291 I 314), solid hydrocarbons a t low temperature ( 9 ) , propane and deuteropropane (200), ozone (10, 126), sulfoxides and sulfones (19),sulfur monoxide (148),acetylene (22), dimethyl diacetylene (6S), and deutero halogenated acetylene (259), fluorine monoxide (27), sulfur (28), aldehydes and ketones (38),tetrahydropyran and p-dioxane (49), perfluorocyclobutane (60, 91), perfluoropropane (go),vinyl chloride, fluoride, vinylidene fluoride, and glyoxal ( 6 8 ) , borine carbonyl (72), ammonia and arsine (85), tartrate ion (88),methane (140),halogenated and deuteroniethane (104, 201, ,“05,211, 255, 946, 2$8,253), methyl chloroform (162), methyl fluoroform (125), hydrogen peroxide (1I S , 304), benzene (145, 208), and substituted benzene (116), nonnietallic hydrides (135), the HD molecule (138), carbonyl chlorofluoride (25O), nitrosyl halides (1.52, 34.5), carbon monofluoride (151), isothiocyanic acid (1,53,ass),isocyanlc acid (154), aluminum hydride ion (188), cyclo-octatetraene ( 189, 2/76), iodine pentafluoride and heptafluoride (IQS),ammonia and hydrogen chloride in the far infrared (100 to 600 microns) (196), allene (216), halogen acids including isotopes (222,X U ) , ammonium nitrate, thallous nitrate, plumbous nitrate (283, 224), ammonium halides (328, S29), diatomic hydrides (344,d?6), thiabutane (25’.5w),nitrous oxide (8257,658,26f ), cyanogen chloride v i t h isotopic carbon (230,260), tetramethyllead (278), iron carbonyls (%77), spiropentane (,%“(I), tertbutyl halides (680), isopropyl halides (281), methyl chlorosilanes (ass), cyclopropane (288), nitroparaffins (292), perfluoroparaffins (299), the carboxyl group (SOT), methanethiol (Sob’), paraffin hydrocarbons (317), monodeuterotoluenes (32S), and urea (830). LITERATURE CITED ( 1 ) Adler, H. H., Bray, E. E., Stevens, K. P., Hunt, J. M., Keller,
W. D., Pickett, E. E., and Kerr, P. F., Am. Petroleum Inst., New York, Project 49, Preliminary Rept. 8 , 1950.
9 ( 2 ) Allen, H. C., Jr., Cross, P. C., and King, G. W., J . Chenk. Phys. 18,1412 (1950) (3) Allen, H. C., Jr., Cross, P. C., and Wilson, M. K., Ibid., 18, 691 (1950). (4) Anantakrishnan, S.V., Proc. I n d i a n Acad. Sci., 30A, 23 (1949). ( 5 ) Anderson, S., J . Am. Ceram. SOC.,33, 45 (1950). (6) Anderson, S., Anderson, W. J., and Krakowski, M., Rev. Sei., Instrzsments, 21, 574 (1950). (7) Anderson, W. E., and Barker, E. F., J . Chem. Phys., 18, 698 (1950). (8) Arnett, R. L., and Crawford, B. L., Jr., Ibid., 18, 118 (1950). (9) Axford, D. W. E., and Rank, D. H., Ib,I.,P h y s . Rev., 77, 150 (1950). (218) Miaushima, S., and Morino, Y.. J . Chenz. P h y s . , 18, 1516 (1950). (219) Miaushima, S., Simanouchi, T., and Tsuboi, M., Satzare, 166, 406 (1950). (220) Rlochel, W.E., and Hall, hl. B., J . Am. Cheni. Soc., 71, 4082 (1949). (221) hlorino, Y., Mizushima, S.,Kuratani, K., and Katayama, M., J . Chem. P h y s . , 18,754 (1950). (222) NaudB, S. hl., and Verleger, H., Proc. Phys. Soc. ( L o n d o n ) , A63,470 (1950). (223) Xewman, R., and Halford, R. S., J . Chem. P h u s . , 18, 1276 (1950). (224) Ihid., p. 1291. (225) Nielsen, H. H., Phys. Rev., 78, 415 (1950). (226) Nielsen, H. H., and Oetjen, R. A., “Physical hfethods in Chemical Analysis,” Berl, W. G., ed., pp. 333-404, New York. Academic Press. 1950.
11 (227) Nielsen. J. R., and Claassen, H. H., J . C h m . Phys., 18, 485 (1950). (228) Ibid., p. 812. (229) Nielsen, J. R., Claassen, H. H.. and Smith, D. C., Ihid,, 18, 1471 (1950). (230) Nixon, E. R., and Cross, P. C., Ibid.. 18, 1316 (1950). (231) Noble, R. H., and Nielsen, H. H., Ibid., 18, 667 (1950). (232) O’Neal, AI. J., Jr., ANAL.CHEM.,22, 991 (1950). (233) Opler, A., Ibid., 22, 558 (1950). (234) Orr, S.. and Thompson, H. W.,J . Chem. Soc., 1950, 218. (235) Pace, E. L., J . Chem. P h y s . , 18, 881 (1950). (236) Pauncz, R., Acta Univ. Szeged., Chem. et Phys., 2, 178 (1949). (237) Pearse, R. W. B., and Gaydon, A. G., “Identification of Molecular Spectra,” London, Chapman and Hall, 1949. (238) Penner, S. S.,J . Applied Phys., 21, 685 (1950). (239) Perry, J . d.,Sutherland, R. G., and Hadden, N.. .ix\I.. C H E Y . , 22,1122 (1950). (240) Petrie, TV., P h y s . Rev. 77, 720 (1950). (241) Pirlot, G., B u l l . soc. chim. Bdg., 59, 5 (1950). (242) Ibid., p. 327. (243) Ibid., p. 352. (244) Platt, J . R., J . Chem. P h y s . , 18, 932 (1950). (245) Pliva, .J., and Sorm. F., Collection Czechoslov. Chem. Coinmima., 14,274 (1949). (246) Plyler, E. K., and Lamb, hl. .i., .J. Resenrch Nntl. Bur. Standards, 45,204 (1950). (247) Plyler, E. K., and Rowen, J . IT., Ibid., 44, 313 (1950). (248) Pluler, E. K., Smith, M’. H., and .4cquista N., Ibid.. 44. 503 (1950). (249) Prime, H. A . , Research, 3, 51 (1950). (250) Prudhomme, A , Bnn. Geophus., 5, 236 (1941)). (251) Rank, D. H., and Axford, D. W.E., .I. Chem. Phys., 17, 1339 (1949). (252) Rank, D. H., Shull, E. R., and Axford, D. W.E., Ibid., 18, 392 (1950). (253) Rank, D. H., Shull, E. R., and Pace, E. L.. Ibid., 18, 885 (1950). (254) Rao, K. N., Ibid., 18, 213 (1950). (255) Rasmussen, R. S.,Fortschr. Cheni. Org. Naturstofle, 5, 331 f 1 R48). - ~ , I--
(256) Reid, C., J . Chem. Phys., 18, 1512 (1950). (257) Rhodes, K. B., and Bell, E. E., Phys. Rev., 76, 1273 (1949). (258) Rhodes, K . B., and Bell, E. E., V i r g i n i a .J. Sci. [NS],1, 227 (1950). (259) Richardson, W.S., and Goldstein, .J. H., J . Chern. Phys., 18, 1314 (1950). (260) Richardson, W. S.,and Wilson, E. H., Jr., Ibid.. 18, 155 (1950). (261) I b i d . , p. 694. (262) Ritter, E. S., ,Ccience, 111, 685 (1950). (263) Rodionov, 9. F., and Pavlova, E. N.,Doklndy A L a d . Y a u k S.S.S.R., 65,831 (1949). (264) Rosenkranta, Harris, and Mlhorat, .4. T., J . A m . Chem. SOC., 72,3304 (1950). (265) Rupert. C. S.,and Strong, J., J . Optical Sor. d i n . , 40, 455 (1950). (266) Saksena, B. D., and Narain, H., Nature, 165, 793 (1950). (267) Saksena, B. D., and Narain, H., Proc. Indian A d . Sci., A30, 128 (1949). (268) Saviteky, A , , and Halford, R. S., Rev. Sci. Instruments, 21, 203 (1950). (269) Schoen, J., Arch. tech. Messen, 170, 725 (1950). (270) Scott,, D. W.,Finke, H. L., Hubbard, W. N., hIcCullough, J. P., Gross, 54. E., Williamson, K. D., Waddington, G., and Huffman, H. AI., J . Am. Chem. Sac., 72, 4664 (1950). (271) Scott, G. P., and Tarbell, D. S., Ibid., 72, 240 (1950). (272) Sears, W.C., and Kitchen, L. J., Ibid., 71, 4110 (1949). (273) Sevchenko, 9.N., and Stepanov, B. I., J . E s p t l . Theoret. P h y s . , U.R. S. R., 19, 1113 (1949). (274) Shaw, J. H., Chapman, R. M., and Howard, J. X . , Phys. Rev., 79, 1017 (1950). (275) Sheline, R. K., J . Chem. Pliys., 18, 602 (1950). (276) Ibid., p. 927. (277) Sheline, R. K., and Pitaer, K. S.,,J. Am. Chem. S O C . , 72, 1107 (1950). (278) Sheline, R. K., and Pitzer, K. S., J . Chem. Phys., 18, 595 (1950). (279) Sheppard, N., T r a n s . Faradny Soc., 46, 429 (1950). (280) Ihid., p. 527. (281) Ibid.,p., 533. (282) Sheppard, N., and Szasa, G. J., J . Chem. P h y s . , 18, 145 (1950). (283) Shimanouchi, T., Tsuchiya, I., and hlikawa, Y., Ibid.,18, 1306 (1950). (284) Short, L. X., and Thompson, H. W., Nature, 166, 514 (1950). (285) Shreve, 0. D., and Heether, bl. R., ASAX,. CHEY.,22, 836 (1950). (286) Shreve, 0. D.. Knight, H. 13.. and Swern, D., I b i d . , 22, 1261 (1950).
12
ANALYTICAL CHEMISTRY
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UItraviolet Absorption Spectrophotometry E. J. ROSENBAUM, Sun OiI Co., Norwood, Pa.
F
ROM a survey of the literature on ultraviolet absorption spec-
trophotometry published during the past year, several trends can be identified. There s e e m to be a growing interest in the determination of inorganic compounds by this method. An increasing number of spectra have been obtained %-ith the Cary recording spectrophotometer which, u p to the present,, has had only a very brief description in the literature (Sf). The rate a t which spectra are being published continues to be high, b u t only a minor fraction of these spectra are applied to analytical problems, the major interest being usually in a correlation of spectra with molecular structure. Little has appeared on instrumental or apparatus development. Papera by Kinsey (22) and by Shugar (So') deal with the problem of using the Beckman quartz spectrophotometer for the analysis of very small samples. Microcuvettes and methods for positioning them are described. A review on microsp ec-
troscopy by Loofbourow (23) includes a description of methods of obtaining ultraviolet absorption spectra of minute samples. Bastisn, Weberling, and Palilla (1) discuss the use in spectrophotometric analysis of a reference solution which contains the absorbing component of interest. They illustrate the advantagee of this differential method, b u t point out t h a t i t requires wider slits than would otherwise be necessary and t h a t in some case8 the resulting loss of resolving power and increase in stray radiation might be a handicap. An interesting variation of the usual procedure for multicomponent quantitative analysis is presented by Perry, Sutherland, and Hadden (52). I n setting u p their calibration they use measurements on solutions of the individual components whose concentrations are not known, the only requirement being t h a t the absorbances (optical densities) fall within the optimum range of 0.4 to 1.0. I n addition, measurements on one mixture of known composition must be used. The
