ANALYTICAL CHEMISTRY
1890 Image Defects. JAMES HILLIERAND 8. G. ELLIS,RC.4 Research Division, Princeton, N. J. The detection and possible elimination of image defects due to power supply variations, stray magnetic fields, vibration, specimen drift, etc., were surveyed. Some of this information has been pubIished, but the review was desirable for many. Thermal drifting
of the specimen may be lessened by not allowing the specimen holder to cool off during specimen changes. The second Portion of this paper described the experimental procedure for adjusting the screws in a n objective pole piece compensating spacer for correcting the lens asymmetry before and during the compensation.
Southwest Regional Meeting HE Seventh Southwest Regional Meeting of the A ~ : H I CsA C ~ SOCIETY ~ ~ was~ held~ a t Aust,in, a ~ Tex., Decemher 6 t o 8, 1951. Abstracts of the papers present,ed before the .knalyticnl Section are given below. T
Application of the Venenate Method to Determination of Calcium A N D C. T. and Magnesium in Limestones. JOHXJ. BANEWICZ XENNER, Southern Methodist University, Dallas, Tex. The Diehl, Goetz, and Hach method for the determination of total hardness in water has been applied to the determination of both calrium and magnesium in limestones. The method involves the titration of aliquots of a solution prepared by dissolving a 1-gram sample in dilute hydrochloric acid, followed by adjustment of pH and dilntion to 500 ml. The magnesium end point was sharpened considerably by the addit,ion of hydrogen peroxide after filtration of the calcium oxalate. The method was tested with Bureau of Standards limestone samples. Spectrophotometric Determination of Magnesium. JVLIVS AI. KOMARY, GEORGE M. WYATT, A K D AUBREYE. HARVEY, J R . , Chemist r y Department, University of Arkansas, Fayetteville, Ark. The highly colored complex formed by magnesium and nitrosulfonaphtholaeo-1-naphthol (Eriochrome Black T) has been used a.q a basis for a new spectrophotometric method for the determination of this element. The slightly dissociat,ed, soluble, red complex forms in the p H range of 7 to 10. Schwareenbach and Biederman [Schwareenbach, G., and Biederman, IT.,X e h . Chim. Acta, 31, 678 (1948)] reported that the complex is formed by the combination of one magnesium ion with 1 mole of the reagent. The method of continuous variations, however, indicates an empirical formula of MgRz the complex a t a pH of 10.1. ’ forThe optimum conditions for the method have been determined. A procedure has been developed for avoiding interference from calcium, which also forms a red complex with the reagent. The determination of calcium with this reagent is also being investigated. Isolation and Detection of Chromium by Extraction of Perchromic Acid. PHILIP WEST, NANCY ROBERTS, AND JACK K. c . 4 R I . T O S , Louisiana State University, Baton Rouge, La.
w.
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The oxidation of chromic salts, dichromates, and chromates to the intense blue perchromic acid has served as a very sensitive means for detecting chromium. Sensitivity and selectivity are increased by extracting the colored compound with organic solvents. The authors propose the use of sodium peroxide a3 oxidant and trichloroacetic acid as a buffer to attain optimum conditions for extraction. Employing ethyl acetate as solvent, i t was found that as little as 1 microgram of chromium could be detected with very few interferences and that a solution containing a s much as 7.0 mg. of chromium could be completely extracted in a single pass. The interference of iron was obviated by complexation with phosphoric acid. Studies made on the color stability of the extract phase and upon the conformance of the system to Beer’s law establish the possibility of adapting the procedure to the colorimetric determination of chromium. Color Reactions of Aromatic Hydrocarbons with Ninhydrin in Sulfuric Acid. THOM.4S R. BLOHM,University of Texas, Houston, Tex.
It has been discovered that ninhydrin in concentrated sulfuric acid gives color reactions with submilligram quantities of aromatic hydrocarbons. This is related to formaldehyde-sulfuric acid (Marquis’ reagent), but the colors obtained with ninhydrin are soluble and characteristic of the hydrocarbon, while those obtained with Marquis’ reagent are insoluble and indistinguishable from one another. I n small quantities alkanes do not give colors, but in 100-mg. quantities they do, Unsaturated hydrocarbons are intermediate in chromogenic power between alkanes and aromatics. Phenols are powerfully chromogenic. Meta-directing substituents on aromatic nuclei prevent reacfion with ninhydrin-sulfuric acid.
-1 number of miscellaneoiiv compounds of general and biological interest were tried with this reagent, and the results were reported. Some photochemical reactions were observed. The analytical use of the reagent will be limited by its nonspecifirity, hut because of its other desirable characteristics it may he yery useful when applied to selected material. Adaptation of Phenoldisulfonic Acid Method for Nitrates to Quantitative Photoelectric Colorimetric Analysis. J. M. KOMARYY, \I., J. B ~ o a c AND ~ , M. K. TESTERXLN, University of Arkansas, Fayetteville, Ark. Use is made of the phenoldisulfonic acid method heretofore applied to water analysis, where the nitrate content is estimated by visual (.olor comparison. Modification of this method has been accomplished whereby the concentration of the yellow phenoldisulfonic acid-nitrate complex may be accurately measured by means of a Nett-Summerson photoelectric colorimeter such that the lead in the sample being analyzed may be calculated with an accuracy of 1 1 % . -1bsorption spectra for the colored complex have been determined. The Klett photometer necessitates the use of a filter for wave lengths longer than that of maximum absorption. This fact probably explains the nonlinearity of the curve of optical density versus concentration. However, the resulting curve may be described very a r m rately by an equation of the form log I l l 0 = dc?
+ h’c + B
T\here the constants A , K , and B are evaluated from samples of known nitrate concentration. The optical density of the phenoldisulfonic acid-nitrate complex has been found to he constant for several hours. .halysis must be performed on only perfectly dry samples. This also includes samples containing hydrates or hydroxy compounds where they are on the borderline of being considered as hydrates. Use of Radioactive Isotopes in Determining the Efficiency of Chemical Separations. MAURICE M. VICK A N D 1.DYERL - ~ F L E U R , Louisiana State University, Baton Rouge, La.
.1 study of the chemiral separation of cations effected in the process of a new nonsulfide scheme of qualitative analysis is being made in order to determine the completeness and quality of such separations. The paper dealt with a measurement of the Completeness of precipit,ation in the removal of the fluoride group, composed of lead, magnesium, barium, strontium, and calcium by treatment with a saturated sodium fluoride solution a t a pH of approximately 5 (Zk0.1)~ The isotope dilution method of analysis has been used to follow the 1,eactions involving barium, strontium, and calcium, individually. The lead analysis remains to be run and the magnesium study has been traced by other methods due to the shortness of half-life of the radioactive magnesium isotopes. I n t,he procedure, a calculated amount of the radioactive isotope is added to the solution to be precipitated, an aliquot of the solution is ronnted, and another aliquot is treated with the precipitant. The centrifugates, washings, and dissolved precipitates are each counted separately and the completeness of precipitation is calculated. Care is taken that the geometry, matrix of residual salts in solution, and pH are comparative. The results indicate a complet,eness of precipitation well within the limits required for analysis. Spectrophotometric Studies of Empirical Formulas of Complex Ions. DELMERL. MANNING AND AUBREY E. HIRVEY. JR.,Chemistry Department, University of Arkansas, Fayetteville, Ark. Empirical formulas for three complex ions have been established. Good agreement was obtained with several different methods. Titanium(1V) and Tiron (disodium 1,2-dihydroxybenzene3,5-disulfonate monohydrate) combine in a molar ratio of 1 to 6 to form a yellow complex.
1891
V O L U M E 23, NO. 1 2 , D E C E M B E R 1 9 5 1 il formula of FeRs has been assumed for the blue complex, which i s the oxidation product of the red, iron(I1)-orthophenanthroline complex. This formula was verified. The yellow complex which forms when orthophenanthroline is added directly to iron(II1) was found to have a formula of FeXRs. It was observed that the blue complex formed by oxidation changes on standing 4 days to the yellow complex. New Polarographic Electrode
Employing Controlled
Stirring.
PAUL ARTHUR,R . F. h‘kxES8, J. KOMYATHY, AND H . VAUGHN, Oklahoma Agricultural and Mechanical College, Stillwater, Okla. A new electrode which makes use of the controlled stirring obtained when a stationary electrode is inserted upward into the lower end of a rapidly revolving stirring tube was designed by Arthur and Maness in 1949. With electrode tubes 1.7 to 3.5 mm. in inside diameter filled with mercury and a t a stirring speed of 600 r.p.m., excellent polarograms with no oscillations, very large diffusion currents, and even less residual current than is obtained with the conventional D.M.E. are obtained. Various modifications, including use of an amalgamated platinum collar just inside the upper end of the electrode tube to prevent “creeping” of the solution, and stirring of t,he soliition by means of a solid glass rod insei ted into the upper end of the electmde tube were described.
Polarographic Study of the Kinetics of Ionic Recombination and DELAHAY A X D THOMAS Comparison with Onsager’s Theory. PAUL J. .LDAMS, Louisiana State University, Baton Rouge, La. .\n equation for the rate constant of processes involving the recombination of two univalent ions is derived from Onsager’s theory of ionic recombination. The temperature coefficient of the rate constant is essentially the same as for a diffusion process. The theoretical results were compared with polarographic data for the recombination of pyruvate and hydrogen ions. The dependence of the rate constant on ionic strength was studied experimentally, and the results were analyzed on the basis of the Debye-Hockel theory. Finally, the influenre of the rate of the electrode process in polarographic studies of ionic recombination was disrussed quantitatively.
N. Polarography of Salicylic Acid. CECILH. HALEA N D XLRGIE HALE, Southwestern Analytical Chemicals, Austin, Tex. H;ilic.ylic acid has been found to be reducible a t the dropping mercury electrode to give one well-formed wave. The half-wave potential is - 2.4 volts m. the saturated calomel electrode in 0.1 .M tetrabutylammonium or methyltributylammonium hydroxide. Studies have been made of the effects of temperature, p H , concentration, and presence of more easily reduced ions on the diffusion current and half-wave potential. At constant temperature, the diffusion current is propoi.tiona1 to the concentration of salicylate over the range investigated. 0.001 M to 0.01 .If. The diffusion current increases 270 per degree centigrade rise in temperature. Polarography of Acid Halides in Anhydrous Acetone. PACL oss, Oklahoma Agricultural and Mechanical As a part, of a study of special techniques required and the polarographic behavior of common substances in various anhydrous organic solvents, several acid halides were studied in anhydrous acetone eaturated with lithiumchloride as carrier. The M 2 ’ 3 t 1 ’ 5 was 2.11 when measured at 30’ C. a t - 1.50 volts versus a reference electrode whirh was analogous to the S.C.E. except that anhydrous acetone saturated with lithium chloride was used as the electrolyte. Tests showed this reference electrode to be constant and reversible within f0.001 volt. Certain special techniques were developed. Acetyl, propionyl, butyryl, isovaleryl, @-phenyl propionyl, and benzoyl chlorides and acetyl and propionyl bromide gave Dllz values of -1.30, -1.28, -1.27, -1.28, -1.27, -1.10, -1.21, and -1.28 volts versus the acetone-saturated calomel electrode.
Dielectric Constant Measurement for Continuous Determination
of Toluene. B. W. THOMAS,F. J . FEAGIN, A N D G. W. TTILSOS, Humble Oil and Refining Co., Baytown and Houston, Tex. high frequency dielectric constant instrument has been built for measurement of toluene in four different hydrocarbon streams once per hour. Laboratory analyses of the stream samples weie employed for calibration of the analyzer in the 0 to 100% toluene range. The system consists of a crystal controlled oscillator, a variable frequency oscillator containing a capacitance sample cell, a beat frequency meter, and circular chart recorder. Sample temperature in the capacitance cell is maintained constant and switdhing of streams is accomplished through use of solenoid valves and a cycle
timer. Accuracy of the measurement is =k 1% toluene throughout the range. Analysis of a Mixture of Hydroxy Acids. TONYOSTROFFA N D OGDEN BLINE,Southern Methodist University, Dallas, Tex. The problem consisted in the spectroscopic analysis of a threecomponent mixture of hydroxy aromatic acids with overlapping absorption bands. The usual method involving the use of extinction coefficients was applied but was unsatisfactory because of the failure of two components to follow Beer’s law. The method of Vaughn and Stearn was applied to the mixture. This method consists in preparing a reference chart based on the difference in optical density a t specified wave lengths. The chart is in the shape of a triangle with each corner representing the optical density of a pure component a t a definite concentration. The optical density readings used to obtain the points in the triangle were made on prepared mixtures. The composition of a solution of the three acids can then be found by plotting its difference in optical densities on the chart. Determination of Lead by Centrifugation of Lead Sulfate. R I C H ~ R D J A M E S T. JONES, OTTO L. wILLB.ANKS, . U i D c. T. KEXNER, Southern Methodist University, Dallas, Tex.
c. J.ARN.AGIN,
A rapid method for determination of lead by centrifugation of lead sulfate was proposed. Factors which affect t,he particle size, uniformity, and solubility of the precipitate and thus the apparent centrifuged density must be kept constant. These include the concentrat,ion of nitric acid, the concentration of sulfuric acid, the concentration of lead, the temperature of precipitation, and the time and rate of centrifugation. The method is accurate to &0.5% of the amount present for lead percentages of 50 to 100 on a 1-gram sample and is suggested as a control method. The effects of variations in the various factors which affect the apparent centrifuged density of lend sulfate have been determined. Spectrographic Determination of Palladium, Platinum, Iridium, and Rhodium. Porous Cup Technique. GILBERTH. AYREJ A N D EUGENE W.BERQ,The University of Texas, Austin, Tex.
h direct spectrographic method for the simultaneous determination of palladium, platinum, iridium, and rhodium in solution has been developed, utilizing a high voltage spark source and the porous cup electrode technique. The platinum metal chlorides were used in hydrochloric acid solution. Cobalt(I1) was added as the internal standard, and the intensity ratios Pd 3242.7/Co 3354.4, P t 2830.3/Co 3354.4, I r 3220.7/Co3354.4, and Rh 3323.1/Co 3354.4 were calculated. These line pairs gave normal spectrographic working curves. An average relative analysis error of 2.8% was found for samples with widely varying ratios of the platinum metals. The method is rapid and specific. The method has been applied in a study of the separat,ion of palladium from the other platinum metals by precipitation with dimethylglyoxime, and will be used in further investigations of the sharpness of separations of the other platinum metals by precipitation procedures. Measurement of Chlorine Residual in Water When Nitrogen Trichloride Is Present. C. H. CONNELL,G. C. GAEKE,JR., A. L. WALKER,JR.,AND IVYJONESMATHER,Department of Preventive Medicine and Public Health, University of Texas Medical Branch, Galveston, Tex. Nitrogen trichloride, frequently formed in chlorination of water, sewage, and industrial wastes, is not quantitatively measured by analytical procedures commonly used for chlorine residuals. A sulfite modification of the standard iodometric procedure has been developed which measures the total of nitrogen trichloride along with other forms of available chlorine. Sulfite reduces nitrogen trichloride quantitat,ively to ammonia and chloride, whereas reduction by iodide and arsenite, the reducing’agents commonly used in iodometric methods for chlorine, is only 70 t o 80% complete. A satisfactorily stable sulfite solution is prepared in p H 4.0 acetate buffer solution containing 2 to 5% isopropyl alcohol as the principal oxidation inhibitor. The steps of procedure then for chlorine residual measurement are: 1. -4ddition to a sample of a measured-volume-excess of a sulfite solution of convenient strength. 2. Addition of a measured-volume-excess of iodine solution of convenient strengt,h. 3. Acidification of the sample to pH 3.0 to 3.5 and titration of the excess iodine with standard thiosulfate solution. 4. Simultaneously (or within 30 minutes) assaying the strength of the sulfite solution by applying the above three steps of procedure to a water blank.
1892
A N A L Y T I C A L CHEMISTRY
The precision of the procedure is of the same order as for the standard iodometric method, equal to that of the standard o-tolidine procedure for residuals as low as 1 p.p.m. and better than that of the o-tolidine method for residuals above 5 p.p.m. For samples containing no nitrogen trichloride but other forms of available chlorine, the procedure checks closely results obtained by iodometric and o-tolidine methods. For samples containing chlorine residual only in the form of nitrogen trichloride, the procedure gives results approximately 25% higher than results obtained by iodometric and o-tolidine methods. On this basis, it is possible to estimate the amount of nitrogen trichloride in samples containing, in addition, other forms of available chlorine.
proved by a comparison of the epectral curve of the product with that of chloroplatinous acid. The standard methods for the spectrophotometric determination of the stoichiometry of complexes gave some information, but the results were insufficient for exact determination. The method of Vosburg and Cooper indicated an initial reaction between 1 mole of platinum(1V) and 1 mole of tin(I1) to yield a relatively uncolored product, presumably platinum(II), and further interaction with from 3 to 5 moles of tin to give the colored species. Similar results were obtained using platinum(I1) and tin(II), and it was again found impossible to differentiate between the three po8sible complexes. The method of Molland did not indicate a definite complex: Depending on the wave length a t which it was measured, a ratio of tin to platinum of from 3 to 16 was found. This indicated that a t least two colored species were formed. A study of the distribution between aqueous and organic phases yielded more positive results. The higher alcohols were found to give more complete extraction and more stable solutions than the ethers and esters originally recommended in analytical procedures. Khen the extraction is performed with capryl alcohol, 3 moles of tin(I1) are extracted with each mole of platinum(I1). Equilibrium measurements in the presence of varying amounts of excess tin(I1) indicate possible further reaction in the aqueous phase to form a complex containing 4 moles of tin for each mole of platinum. At optimum tin concentration (approximately 0.04 molar in the aqueous phase), the platinum distribution ratio i s approximat.ely 20,000 t o 1.
Chloroform Extraction of Copper(I1) and Nickel(I1) Salicylaldoximate. J. B. MaRTIN AND S. H. SIMONSEN, University of Texas, Austin, Tex. The chloroform extraction of copper(I1) and nickel(I1) salicylaldoximates was studied quantitatively, and the extractability constants, K , evaluated. The distribution of salicylaldoxime between chloroform and aqueous solutions was determined by shaking standard solutions of the reagent in chloroform with various buffers of pH range 1.0 to 11.0. The concentration of the salicylaldoxime was determined spectrophotometrically in the chloroform layer after equilibrium had been attained. The distribution of copper(I1) and of nickel(I1) salicylaldoximates was determined in a similar fashion, and the extractibility constants were found to be 9.3 =t 0.5 and 3.3 =k 0.5 X 10-8, respectively. Because of the widely differing values of the constants, the separation of Cu(I1) and Ni(I1) by chloroform extraction of the salicylaldoximates is possible by control of the acidity of the solutions. The separation of copper(I1) and nickel(I1) and the spectrophotometric determination of the copper was tested by analysis of National Bureau of Standards, Standard Sample 85a, wrought aluminum alloy (2.48% copper and 0.417, nickel). The relative error for a triplicate series of determinations was 0.8% and the average deviation (absolute) was 0.03%. Composition of the Basic Ferric Formate Precipitate. NELSON A. LLOYD,MCGEEA. DUFF, AND C. T. KENNER,Southern hlethodist University, Dallas, Tex. The basic ferric formate precipitate is composed of two distinct aubutances, one amorphous and the other crystalline. The major portion of the precipitate is amorphous, reddish in color, and insoluble in benzene. A minor portion of the precipitate is crystalline and soluble in benzene, from which it may be crystallized by evaporation of solvent. Slides showing the prmence of amorphous and crystalline material together were presented. The basic ferric acetate precipitate is composed of crystalline and amorphous substances also. Fusion Method for Microscopic Identification of Inorganic Ions. P H I L I P Jy. WEST A N D LlWRENCE GRANATELLI, Louisiana State University, Baton Rouge, La. This investigation was initiated in order to determine whether the fusion of inorganic salts with 8-quinolinol could be employed for the microscopical detection of the inorganic ions in these salts. By fusing inorganic salts with 8-quinolinol on a microscope hot stage the following ions may be identified by studying the color, niorphology, and certain optical properties of the addition and chelate salts thus formed: nitrate, chloride, sulfate, copper, zinc, uranyl, calcium, chromium, and magnesium. Bubble formation occurring in the temperature range 100’ to llOo is indicative of the presence of water of crystallization in the inorganic salt. The technique described is of special interest because it permits, in many cases, the simultaneous identification of cation, anion, and water of crystallization in a given inorganic salt. The melting point of the inorganic salt examined need not be approached before characteristic crystals of the chelate or addition products are formed. Interaction of Platinum(1V) and Tin(I1) Chlorides. GILBERTH. -XYRES AND ALBERTS.MEYER,JR.,The University of Texas, Austin, Tex. During the development of a spectrophotometric method for the determination of platinum by the reaction between platinum(1V) and tin(I1) chloride, it was observed that the properties of the colored product formed were not compatible with previously proposed explanations. The observations that the colored species passes rapidly through semipermeable membranes, extracts rapidly into organic solvents, and oxidizes to colorless solutions on exposure to the atmosphere are not in agreement with the original suggestion that the color is due to a protected metal colloid. And the more recent suggeation that the color is due to chloroplatinous acid is easily dis-
Society for Applied Spectroscopy T h e Society for Applied Gpect’roscopy will meet January 8, 1952, for informal dinner a t Towa’s, 118th Fulton S t . , S e w Tork, A-. Y. T h e regular nirrting will be held at 8 P.M. a t t,lie Socony-Vacuum Training C’ciit rr, 63 Park Row, New Torli. E. J. Serfass, Lehigh L-niver+ity. will speak on “Surface Analysis with the Photoelectric Sprc*tronwtrr.’’
Symposium on Molecular Structure ’l’lie Symposium on ~ I o l r c ~ ~Structure l~rr and Spectroscopy M 111 Iw held a t t h e Department of Phvsics and Astronomy, Ohio *tate Vniversity, Colunihus, Ohio, from June 9 to 13, 1952. There n ill be discussions of the inteiprrtation of molecular spectro-topic d a t a as well as method* foi obtaining such data. O t h r r vssions n-ill be devotrd to phacr\ o f spectroscopy of cumen t interest Information m a y be obtained from Harald H. Nielsen, DeImrtment of Physics arid Astronomy. Ohio State Universiti-, Columbus 10, Ohio.
1
Fifth Annual Symposium on Modern Methods of Analytical Chemistry. Louisiana State Cniversity, Baton Rouge, La., January 28 t 3 31, 1952 American Society for Testing Materials. Committee D-2 oil Petroleum Products and I~ubrirants,Washington. D. C.. February 3 to 8, 1952 Symposium on Analyses Relating to Manufacture of Butadiene. Office of Rubber Reserve and Technical Committee H of ASTJI D-2. Washington, D. C., Februar!. 1952 Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy. William Penn Hotel, Pittsburgh, Pa.. March 5 to 7 , 1952 Symposium on Molecular Structure and Spectroscopy. Ohio State University, Columbus, Ohio, June 9 to 13, 1952 Fifth Annual Summer Symposium. Michigan State College. East Lansing, Mich., June 20 and 21, 1952 International Congress on Analytical Chemistry. Oxford. .England, September 4 to 9. 1952
