AC BRIEFS Radiochemical Determination of Ionium in Uranium Fluorination Ash
Ionium (thorium-230) is determined in uranium fluorina tion ash by a carrier-free radiochemical method. Ex traction by a combination of lanthanum hydroxide and fluoride precipitations carries the ionium quantitatively. This is selectively removed with 2-thenoyltrifluoroacetone-xylene and the activity measured in a propor tional alpha counter. F. L. M O O R E , O a k Ridge National Laboratory, O a k Ridge, Tenn. Anal. Chem. 3 0 , 1 0 2 0 ( 1 9 5 8 )
Detection of Thorium and Uranium
A qualitative test for the detection of thorium and ura nium is based on their reactivity with EDTA and arsenazo as an indicator. When both are present, separation of uranium with diethyldithiocarbamate is necessary; thorium in the aqueous layer reacts to give a violet color and uranium in the organic layer gives a blue color. Fluoride, oxalate, silicate, tungstate, and vanadate inter fere in thorium detection; large amounts of phosphate interfere in the uranium test. J. S FRITZ and E. C. BRADFORD, Iowa State College, Ames, Iowa Anal. Chem. 3 0 , 1 0 2 1 ( 1 9 5 8 )
G a m m a Spectrometric and Radiochemical Analysis for Impurities in Ultrapure Silicon
Some 29 elements have been determined as impurities in ultrapure silicon using the combined techniques of gamma spectrometry and radiochemical separation with beta counting of the fractions. Impurities are classified into long-lived and short-lived elements according to the half lives produced from neutron activation. Level of determination is in parts per billion. B. A. T H O M P S O N , B. M. STRAUSE, and M. B. lEBOEUF, General Electric Co., Schenectady, Ν . Υ. Anal. Chem. 3 0 , 1 0 2 3 ( 1 9 5 8 )
Determination of Traces of Uranium w i t h 1 -(2-Pyridylazo)-2-naphthol
Trace amounts of uranium can be selectively determined by reaction with l-(2-pyridylazo)-2-naphthol at pH 10. The red colored complex formed is extracted with odichlorobenzene and the density measured at 570 m/z. Reaction proceeds in presence of complexing agents (EDTA). Phosphates and iodine interfere. Hydrogen peroxide inhibits the reaction. K. L. C H E N G
Westinghouse Electric Corp., East Pittsburgh, Pa. Anal. Chem. 3 0 , 1 0 2 7 ( 1 9 5 8 )
Highlights of the contributed articles in this issue
Complexometric Determination of Sulfate
Sulfate content of materials obtained during uranium extraction from ore is determined by complexometric titration using lead nitrate in an acid solution. The precipitate is dissolved in solution of EDTA and excess EDTA is back-titrated with zinc chloride with Eriochrome Black Τ indicator. The method is virtually free of interference. K. F. SPOREK, Eldorado Mining and Refining, Ltd., O t t a w a , Ontario, Canada Anal. Chem. 3 0 , 1 0 3 2 ( 1 9 5 8 )
Redox Behavior of Cobalt Chelates of Nitrilotriacetic Acid
Oxidation of cobalt or iron in the presence of nitrilo triacetic acid (NTA) with hydrogen peroxide produces an intense violet color; with perborate only cobalt responds; this serves as the basis for a spectrophotometric procedure. Factors affecting color formation, pH, time, temperature, and analytical application to determination of hydrogen peroxide, NTA, and other compounds are presented. K. L. CHENG, Westinghouse Electric Corp., East Pittsburgh, Pa. Anal. Chem. 3 0 , 1 0 3 5 ( 1 9 5 8 )
Determination of Nitrogen Dioxide by Gas-Solid Chromatography
Gas-solid chromatographic determination of nitrogen dioxide is possible by conversion to nitric oxide on a water-treated Molecular Sieve column. The conversion eliminates the complication of oxidation of organic partitioning liquids. Wet alumina or silica gel columns can be used. S. A. GREENE and H. PUST, Aerojet-General Corp., Azusa, Calif. Anal. Chem. 3 0 , 1 0 3 9 ( 1 9 5 8 )
Gas Chromatographic Analysis of Engine Exhaust and Atmosphere. Determination of Ci to C5 Hydro carbons
Trace amounts of C2 to Cs hydrocarbons in engine ex haust and city air are determined by a gas chromato graphic procedure. Extraction is through a trapping column of Ascarite immersed in liquid oxygen. Analysis follows elution with helium. With the thermal conduc tivity detector at high sensitivity, the limit of assay is 0.02 p.p.m., which is within the range of interest in air pollution control. F. T. EGGERTSEN and F. M. NELSEN, Shell Development C o , Emeryville, Calif. Anal. Chem. 3 0 , 1 0 4 0 ( 1 9 5 8 )
Determination of Total Fluoride Content in Uranium Tetrafluoride Using Ion Exchange Columns
Ion exchange methods are used to effect rapid separation of total fluorides in uranium tetrafluoride, uranium hexafluoride, and uranyl fluoride. The solid sample is dis solved in a mixture of sodium hydroxide and hydrogen peroxide and then passed over an ion exchange column (Amberlite IR-120). The liberated hydrofluoric acid is titrated with 0.2iV sodium hydroxide. Acids (except carbonic) cause interference; uranium oxides do not in terfere.
Automatic Equipment for Determination of A m i n o Acids Separated on Columns of Ion Exchange Resins
An automatic system is developed for the determination of amino acids in effluent fractions from an ion exchange chromatographic column. Advantages include reduc tion in manual labor and systematic variability in the analyses. The system's capacity of four 2-ml. fractions per hour is its chief disadvantage. Other groups of sub stances can be analyzed by this method if a common colorimetric or spectrophotometric method is available.
K. F. SPOREK, Eldorado Mining and Refining, Ltd., O t t a w a , Ontario, Canada
D. H. S I M M O N D S , Commonwealth Scientific and Industrial Research Organization, Melbourne, Australia
Anal. Chem. 3 0 , 1 0 3 0 ( 1 9 5 8 )
Anal. Chem. 3 0 , 1 0 4 3 ( 1 9 5 8 )
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BRIEFS Partition Separation of Carotenoids by Silica-Methanol Columns
Dyeing Method for Quantitative Determination of Lipicjes a n d Lipoproteins Directly on Filter Paper
Columns of silica gel treated with methanol can effec tively separate the carotenoid pigments of plant tissue into three fractions relative to their solubilities in hexane and methanol. Fractions I, II, and III contain carotene, monohydroxy carotenoids, and polyhydroxy carotenoids, respectively. A. E. PURCELL, U. S. Department of Agriculture, Weslaco, Tex. Anal. Chem. 3 0 , 1 0 4 9 ( 1 9 5 8 )
Paper chromatography of serum lipide fractions is made more accurate and rapid by a quantitative dyeing tech nique. The use of a 50% aqueous solution of diacetin saturated with Oil Red Ο dye at 2 5 ° C. results in a linear relationship between dye uptake and lipide concentra tion. Solubility of the dye in various classes of lipides is the limiting factor. K. F. TALLUTO R. R. BENERITO, and W . S. SINGLETON, U. S Depart ment of Agriculture, N e w Orleans, La. Anal. Chem. 3 0 , 1 0 5 9 ( 1 9 5 8 )
Chromatography of Esters on Florisil. as Ferric Hydroxamates
Detection
Florisil is a suitable adsorbent for the chromatographic separation of fatty esters and acetates. The material is applied to the column in benzene and bands located by streaking with hydroxylamine-ferric ion reagent. Color reaction is completed by heating with infrared lamp. R values for homologous series are recorded. F. B. O'NEAL and JACK CARLTON, Georgia Institute of Technology, Atlanta, G a . Anal. Chem. 3 0 , 1 0 5 1 ( 1 9 5 8 )
Determination of Zirconium in Titanium Using p-Bromo- or p-Chloromandelic Acid
Alloys
Zirconium content of titanium alloys can be determined by dissolving in 1 to 4 hydrochloric acid and precipitat ing the zirconium with/>-bromo- or/>-chloromandelic acid. After igniting the precipitate at 1000° C , weight of ZrOa is determined and calculated as per cent zirconium.. Range of accuracy is 0.1 to 2 %; above 2 % reprecipitation) of zirconium is necessary. R. A. PAPUCCI, F. C. Broeman and Co., Cincinnati, Ohio, and J. J. KLINGENBERG, Xavier University, Cincinnati, Ohio Anal. Chem. 3 0 , 1 0 6 2 ( 1 9 5 8 )
Use of Substitute Standards in Infrared Differential Spectrophotometry
The interference caused by impurities in the reference standard in infrared differential analysis of a compound for a specific impurity is eliminated by substituting another compound as a reference standard. This com pound must possess similar absorptive characteristics. Factors influencing selection of substitute standard are presented. W . H. WASHBURN and M . J. M A H O N E Y , Abbott Laboratories, North Chicago, III.
Coulometric Titrations w i t h Mercury(l) and (II). Determination of Sulfide
The insolubility of mercury (II) sulfide is the basis for a sensitive coulometric titration procedure for sulfide using mercury-coated gold electrodes. The potentiometric end point is a function of the solubility of the precipitate formed. Microgram amounts of sulfide are titrated under specific conditions with an error factor of ± 0 . 2 % . E. P. PRZYBYLOWICZ and L. B. ROGERS, Massachusetts Institute of Technology, Cambridge 3 8 , Mass. Anal. Chem. 3 0 , 1 0 6 4 ( 1 9 5 8 )
Anal. Chem. 3 0 , 1 0 5 3 ( 1 9 5 8 )
Determination of Carbon Dioxide in Automotive Exhaust by Means of Infrared Filter Photometer
An interference filter photometer has been designed for measuring carbon dioxide at 4.29 microns. It has been utilized as a monitor on a gasoline engine exhaust. Photometer values are high compared to Orsat deter mination. J. L. PARSONS, J. C. NEERMAN, J. R. LIFSITZ, and F. R. BRYAN, Ford Motor C o , Dearborn, Mich. Anal. Chem. 3 0 , 1 0 5 5 ( 1 9 5 8 )
Determination of Catalyst Water by Exchange 'with Deuterium Gas
The water content of oxide catalyst is determined quan titatively by isotopic exchange of the hydrogen with gaseous deuterium at 500° C. The method compares favorably with the ignition-loss method and is non destructive for refractory oxides. Presence of volatile components does not interfere. J. K. LEE and S. W . WELLER, Houdry Process Corp., Linwood, Pa. Anal. Chem. 3 0 , 1 0 5 7 ( 1 9 5 8 )
Determination of Cysteine with Ferricyanide by Amperometric Titration with T w o Polarized Electrodes
Semimicro amounts of cysteine in buffered solution (pH 7) can be amperometrically titrated with potassium ferricyanide using two platinum electrodes. End point is reached when a direct current is produced due to unreacted ferricyanide in solution. Other common amino acids do not interfere, but samples must be pro tected from oxidation conditions. H. G. WADD1LL and GEORGE G O R I N , Oklahoma State University, Stillwater, O k l a . Anal. Chem. 3 0 , 1 0 6 9 ( 1 9 5 8 )
Polarographic Study of Cytotoxic Nitrogen Mustards
Reducibility of ethylenimonium cation at the dropping mercury electrode is the basis for a polarographic method. This ion is formed by internal cyclization of the β· chloroethyl group in aliphatic nitrogen mustards. The method is used to study the kinetics of the cyclization and to estimate ethylenimonium intermediates. ROGER MANTSA V I N O S and J. E. CHRISTIAN, Purdue University, West Lafayette, Ind. Anal. Chem. 3 0 , 1 0 7 1 ( 1 9 5 8 )
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BRIEFS Polarographic Estimation of Starch a n d Its Application in Flotation The polarographic procedure for purity determination of starches is modified for starch analysis of flotation liquors. _ Interference by copper and nickel is eliminated by precipitation with thioacetamide. Starch concentra tion must be between 5 and 4 5 0 mg, per liter. Average assay time is 15 minutes. S. C. S U N , D. L LOVE, and R. T. H O L Z M A N N , The Pennsylvania State University, University Park, Pa.
Evaluation of Inert Gas Fusion Method for Rapid Determination of O x y g e n in Steel Modification of the inert gas fusion method gives a rapid and simple procedure for determination of oxygen in steel. The method shows g o o d agreement with the vac uum fusion method. Assay time per sample is 7 min utes. J. I. PETERSON, F. A. MELNICK, and J. E. STEERS, Jr., Jones & Laughlin Steel Corp., Pittsburgh 3 0 , Pa. Anal. Chem. 3 0 , 1 0 8 6 ( 1 9 5 8 )
Anal. Chem. 3 0 , 1 0 7 4 ( 1 9 5 8 )
Condensed Direct Current Arc Excitation for Spectrochemical Analysis of Plant Materials An arc excitation spectrochemical technique permits simultaneous quantitative determination of Ca, M g , P, Fe, Β, Μη, and Cu in plant tissue, from one established set of standard concentration curves. Plant ash in acidic solution is impregnated into powdered graphite held in a cratered electrode—the electrode is dried and excited by means of a condensed direct current arc. Repro ducibility is excellent. H. E. BRAUN, Ontario Agricultural College, Guelph, Ontario, C a n a d a Anal. Chem. 3 0 , 1 0 7 6 ( 1 9 5 8 )
Evaluating Concentrations of Spectrally Absorbing Vapors in Dynamic Systems. Spectrophotometric Techniques and Equipment Use of trace amounts of ammonia in air has been evalu ated as a fumigant to prevent decay in food during ship ment and storage. T o design a balanced system, initial concentration of ammonia, absorption by various foods and fiberboard, and magnitude of the residue were studied. The ultraviolet spectrophotometric technique employed is applicable to any fumigant or vapor that absorbs in the U V region. F. A. GUNTHER, R. C. BLINN, and M. J. KOLBEZEN, University of California Citrus Experiment Station, Riverside, Calif., C. W . W I L S O N , Sunkist Growers, Inc., Ontario, Calif., and R. A. C O N K I N , Monsanto Chemical Co., St. Louis, Mo. Anal. Chem. 3 0 , 1 0 8 9 ( 1 9 5 8 )
Estimation of Tartronate in Tissues A method is devised for the spectrophotometric deter mination of tartronate in plant and animal tissue. De carboxylation of tartronic acid with sulfuric acid gives glycolic acid, which reacts with Eegriwe's reagent and the absorbance characteristics between 500 and 560 m/n are recorded and compared to a standard spectrum. L. G . W E S S O N , Massachusetts Institute of Technology, Cambridge, Mass. Anal. Chem. 3 0 , 1 0 8 0 ( 1 9 5 8 )
Potentiometric Titration of Free A m i n e and A m i n e Carbonate in Carbonated Monoethanolamine Solutions Free and carbonated amines in carbonated mono ethanolamine solutions are determined potentiomettically by double end point titration with hydrochloric acid. End points occur at p H 7 and 4. Titration time is 15 minutes; accuracy within 2 %. Y I - C H U N G C H A N G , U. S. Department of the Interior, Morgantown, W . Va. Anal. Chem. 3 0 , 1 0 9 5 ( 1 9 5 8 )
Mass Isotope Dilution Assay for Gibberellic Acid An isotopic dilution method is developed for the deter mination of gibberellic acid in fermentation beers. A specially prepared deuteriogibberellic acid is the tracer used. Infrared technique is employed to determine per cent deuterium in aqueous isolate. Accuracy is within ± 4 % . Reproducibility is good. B. H. ARISON, O . C. SPETH, and N . R. TRENNER, Merck Sharp &. Dohme Research Laboratories, Rahway, N . J. Anal. Chem. 3 0 , 1 0 8 3 ( 1 9 5 8 )
Estimation of Serum Phospholipide and Total Phosphorus Using Chloric Acid A new reagent is developed to determine phospholipides and total phosphorus in blood serum. Chloric acid di gestion liberates phosphorus which reacts with sodium molybdate. This complex is reduced with hydrazine sulfate to give a blue color. Density measurements are read at 655 and 8 3 0 πιμ. J. F. G O O D W I N , ROGER THIBERT, DAISY M c C A N N , and A. J. BOYLE, W a y n e State University, Detroit, Mich. Anal. Chem. 3 0 , 1 0 9 7 ( 1 9 5 8 )
Rapid Estimation of Hydrofluoric Acid in Red Fuming Nitric Acid The spontaneous current of electrolysis of dilute nitric acid between an aluminum anode and a platinum cathode serves as the basis for the determination of hydrofluoric acid in red fuming nitric acid. Amount of 0.6% (v./v.) can be rapidly and accurately determined with no inter ference from reagent impurities. The method indicates wide applicability. Β. Β. BAKER, Southern Research Institute, Birmingham, Ala. Anal. Chem. 3 0 , 1 0 8 5 ( 1 9 5 8 )
The Rouy Method for Photoelectric Polarimetry A highly sensitive polarimeter can be made from a photo electric colorimeter by using adapters with two sets of polaroids. Each set has the same fixed angle but opposite in sign and has the phase angle greater than 45°. The theory, apparatus, and experimental data of the con version are considered. BENJAMIN CARROLL, H. B. TILLEM, and E. S. FREEMAN, Rutgers, The State University, Newark, N. J. Anal. Chem. 3 0 , 1 0 9 9 ( 1 9 5 8 )
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BRIEFS Identification of Sodium Phosphates with an X - R a y Focusing Camera
Greater resolution and increased definition of the x-ray powder diffraction lines are obtained using a Guiniertype focusing camera. Focusing camera patterns for 60 well characterized sodium phosphates have been re corded. D. E. C. CORBRIDGE and F. R. TROMANS, Albright & Wilson (Mfg.), Ltd., Oldbury, Birmingham, England Anal. Chem. 3 0 , 1 1 0 1 ( 1 9 5 8 )
Determination of Fluoride Ion by Turbidimetric Titration
A turbidimetric titration procedure is developed for determining milligram quantities of fluoride in solution. Calcium chloride is the preferred titrant, but thorium ni trate can be used. The method is based on the lightabsorbing and scattering properties of the formed pre cipitate. Sulfate, phosphate, oxalate, tartrate, aluminum, iron, lead, magnesium, and hydroxyl ions interfere. W . W . BRANDT and A. A. DUSWALT, Jr., Purdue University, Lafayette, Ind. Anal. Chem. 3 0 , 1 1 2 0 ( 1 9 5 8 )
Chelometric Titrations Using an Azoarsonic Acid Indicator
Azoarsonic acid is a suitable indicator for chelometric titration of raw earths and yttrium with EDTA. Opti mum pH range for direct titration is 5.0 to 6.5. Use of masking agents prevents interference of metal ions. Calcium, magnesium, and thorium can be titrated by varying the pH. J. S. FRITZ, R. T. OLIVER, and D. J. PIETRZYK, Iowa State College, Ames, Iowa
Determination of Small Amounts of Arsenic in Selenium
Arsenic, an impurity in rectifier grade selenium, is determined quantitatively by precipitation of selenium with sulfur dioxide and complexing of the arsenic with a molybdate-hydrazine reagent. The blue color formed absorbs at 808 mji; 2 γ of arsenic may be determined. Phosphorus and certain oxidizing agents interfere. J. F. REED, Westinghouse Research Laboratories, Pittsburgh 3 5 , Pa.
Anal. Chem. 3 0 , 1 1 1 1 ( 1 9 5 8 )
Determination of Acids and Basic Nitrogen Compounds in Petroleum Products
Acids and weakly basic nitrogen compounds in petro leum products are determined by nonaqueous titration using a color-indicator system. Acids, particularly where acid number is less than 0.1, are titrated with sodium hydroxide using />naphthalbenzoin indicator. Basic compounds are titrated with perchloric acid using methyl violet. A special flask permitting sharp visual color end points is useful in titrating oils of dark color. IRA KUKIN, Gulf Research & Development Co., Pittsburgh, Pa.
Anal. Chem. 3 0 , 1 1 2 2 ( 1 9 5 8 )
Determination of Titanium in Presence of Niobium by Differential Spectrophotometry
Titanium-hydrogen peroxide complex is the basis for a spectrophotometric method for determination of tita nium in ilmenites. When niobium content is greater than 5 %, a correction factor must be applied; this is separately determined in sulfuric acid solution. Large quantities of iron interfere. R. A. GUEDES de CARVALHO, Bombarda, 1 9 9 , Porto, Portugal
Laboratories
KUDI,
Rua
Miguel
Anal. Chem. 3 0 , 1 1 2 4 ( 1 9 5 8 )
Anal. Chem. 3 0 , 1 1 1 4 ( 1 9 5 8 )
Determination of Trivalent Chromium in the Presence of Chromate
Trace amounts of trivalent chromium (0 to 0.5 p.p.m.) can be accurately determined in water containing 300 p.p.m. chromate. Chromium (III) is precipitated with ammonium hydroxide, using ΑΙ203·Η^Ο as a carrier and then oxidized to chromate with bromine water. Color developed with diphenylcarbazide is measured at 540 ηΐμ. R / W . CLINE, R. E. S I M M O N S , and W . R. ROSSMASSLER, Union Carbide Nuclear Co., Paducah Plant, Paducah, Ky.
Fixation of Atmospheric Carbonyl Compounds by Sodium Bisulfite
A method for determining atmospheric formaldehyde has been improved by cooling the impingers, containing 1 % sodium bisulfite, in ice water to provide a more effi cient trapping system. The aldehyde-bisulfite complex is titrated with standard iodine solution. Other alde hydes and ketones have been determined in air at con centrations between 0.3 and 0.5 p.p.m. K. W . W I L S O N , University of California, Los Angeles 2 4 , Calif. Anal. Chem. 3 0 , 1 1 2 7 ( 1 9 5 8 )
Anal. Chem. 3 0 , 1 1 1 7 ( 1 9 5 8 )
Detection of Polynuclear Hydrocarbons and Phenols with Benzal and Piperonal Chlorides Determination of Silanol with Grignard Reagent
A gasometric method for the determination of the silanol groups employs a Grignard reagent, methylmagnesium iodide in dibutyl ether. The reaction proceeds rapidly at room temperature under an atmosphere of methane. Hydrolysis products from silicone resins and other com plex silanols have been analyzed.
Aromatic hydrocarbons and phenols are determined by a rapid, sensitive method using benzal or piperonal chloride in trifluoroacetic acid to form a diarylmethane dye. A large number of compounds studied indicate that absorption characteristics are dependent upon the nature of substitution groups. Applications are found in air pollution, petroleum, and cancer chemistry fields.
F. O . GUENTHER, General Electric Research Laboratory, The Knolls, Schenectady, Ν. Υ.
EUGENE SAWICKI, ROBERT MILLER, T H O M A S STANLEY, and T H O M A S HAUSER, U. S. Public Health Service, Cincinnati 2 6 , Ohio
Anal. Chem. 3 0 , 1 1 1 8 ( 1 9 5 8 )
Anal. Chem. 3 0 , 1 1 3 0 ( 1 9 5 8 )
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BRIEFS Determination of Aromatic Nitro Compounds
A direct analytical procedure specific for aromatic nitro compounds is based on the reduction of nitro group to primary amine by thiourea dioxide (TUO) in alkaline solution. Diazotization with Chicago acid produces a red color. Excess reductant is destroyed by heating at 50° C. The method is applicable to determination of nitrobenzene and derivatives in urine. W . B. KONIECKI and A. L. LINCH, E. I. du Pont d e Nemours & Co., Inc., Penns G r o v e , N. J. A n a l . Chem. 3 0 , 1 1 3 4 ( 1 9 5 8 )
Spectrophotometrie Determination of Phosphorus in Polyethylene Terephthalate
A semimicro and a micromethod for determination of phosphorus in polyethylene terephthalate is developed. Oxidation is carried out in sulfuric acid-nitric acid solution with perchloric acid (in micromethod the nitric acid is eliminated). A complex formed with ammonium molybdate is reduced with hydrazine to form a heteropoly blue color absorbing at 830 ηΐμ. Arsenic and ger manium interfere. GEORGE TELEP a n d ROBERT EHRLICH, E. I. du Pont d e Nemours & Co., Inc., Kinston, N. C. A n a l . Chem. 3 0 , 1 1 4 6 ( 1 9 5 8 )
Specific Detection of Nitrogen through Pyrolytic Oxidation in Organic Spot Test Analysis Determination of Iodoform by Photooxidation
Iodoform can be quantitatively determined by photooxidation in sunlight. The liberated iodine reacts with a known amount of sodium thiosulfate in solution. At completion the excess thiosulfate is titrated with standard iodine. Acetone can be determined by first being con verted to iodoform. The necessity of sunlight is an inherent disadvantage.
Any nitrogenous compound, volatile or nonvolatile, can be detected by pyrolytic oxidation using manganese dioxide or manganic oxide. Nitrous acid vapor formed reacts with a spot of Griess' reagent on filter paper, giving a pink to red color. FRITZ FEIGL and J. R. AMARAL, Ministerio da Janeiro, Brazil
Agricuttura, Rio de
Anal. Chem. 3 0 , 1 1 4 8 ( 1 9 5 8 )
SAMEER BOSE, Mahakoshal M a h a v i d y a l a y a , J a b a l p u r , India A n a l . Chem. 3 0 , 1 1 3 7 ( 1 9 5 8 )
Simple Microtitrimetric Constant-pH Method for Accurate Enzyme Assays
Enzyme activity can be rapidly and accurately determined by using a microtitrimetric-pH procedure. The increase or decrease in the number of acid groups in the enzymesubstrate system is the basis for the method. Aerobic and anaerobic glycolysis can also be studied. No special or expensive apparatus is necessary. Dithizone Method for Determination of Lead in Monazite
The determination of lead in monazite is made more ac curate and specific by blocking the interference of tho rium and rare earth metals with sodium citrate and po tassium cyanide. Iron is reduced with sulfurous acid. The lead is extracted with dithizone in carbon tetra chloride and absorption measured at 520 mjt. R. A. POWELL a n d C. A. KINSER, U. S. G e o l o g i c a l Survey, Washington 2 5 , D. C. A n a l . Chem. 3 0 , 11 3 9 ( 1 9 5 8 )
MARTIN SCHWARTZ and T. C. MYERS, University o f Illinois College o f Medicine, Chicago, III. A n a l . Chem. 3 0 , 1 1 5 0 ( 1 9 5 8 )
Determination of Mercury in Organic Compounds. Micro and Semimicromethod
The mercury content of organomercurials can be easily determined by combustion of the material in an oxygenfilled flask (Schôniger method) and dissolution of the mercury in nitric acid. The mercury is amperometrically titrated with EDTA at pH 7.5. Presence of chloride ion causes interference. B. C. S O U T H W O R T H , J. H. HODECKER, and K. D. FLEISCHER, SterlingW i n t h r o p Research Institute, Rensselaer, Ν. Υ. A n a l . Chem. 3 0 , 1 1 5 2 ( 1 9 5 8 )
Spectrophotometrie Determination of Chloride in Sweat and Serum with Diphenylcarbazone
Chloride content of sweat and serum is determined by a rapid spectrophotometrie procedure using a mercurydiphenylcarbazone complex. Effect of pH and tempera ture of reaction and stability of the color complex is investigated. Limit of assay is 16 p.p.m. with an ac curacy to ± 2 % . Bromide, cyanide, iodide, and thiocyanate interfere. J. L. GERLACH a n d R. G . FRAZIER, State University o f I o w a , Iowa City, Sowa A n a l . Chem. 3 0 , 1 1 4 2 ( 1 9 5 8 )
Cobalt Determination in Soils and Rocks with 2-Nitroso-1 -naphthol
Trace amounts of cobalt (0 to 10 y) in soils and rocks can be determined colorimetrically by direct reaction with 2-nitroso-l-naphthol. The red colored complex formed is specifically extractable with isoamyl acetate. No pre liminary separation of interfering metals is necessary. Density is measured at 530 rmt. L. J. CLARK, U. S. Department o f Agriculture, Beltsville, M d . A n a l . Chem. 3 0 , 1 1 5 3 ( 1 9 5 8 )
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