Chemical Institute of Canada - Analytical Chemistry (ACS Publications)

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ANALYTICAL CHEMISTRY

1230 Colorimetric Determination of Calcium with Ammonium Purpurate. JAMES H . MOSERA N D M. B. WILLIAMS,Oregon State College, Corvallis, Ore.

A procedure has been developed for the spectrophotometric determination of calcium solutions containing 0.01 (approximately) t o 3 mg. per liter of this metal. The color reagent used was a solution of ammonium purpurate (murexide) in 70% ethanol. T h e optimum p H for t h e analysis was found t o be 11.3, a t a wave length of 506 m p for solutions not containing magnesium and 505 mp for solutions in which magnesium is present. The minimum utilizable concentration of ammonium purpurate in the various solutions is given. Possible errors due t o t h e decomposition of the dye were eliminated by measuring the absorbancies of the calcium solution containing a given amount of murexide against a calcium-free solution containing exactly t h e same given amount of the dye. A comparison of some analytical results was given. Because of the fairly rapid decomposition of murexide in neutral aqueous solutions, a study was made of various solvents, and of t h e solvents investigated: the dye was found to decompose the least in 70% alcohol. The r a t e of decomposition is less a t 4' C. than a t room temperature. It was also found t h a t t h e decomposition of murexide solutions is not affected by light or oxygen. The decomposition products of this dye have no effect on the accuracy of t h e calcium analysis.

T h e effect of various concentrations of cesium, potassium, sodium, lithium, chloride, nitrate, sulfate, magnesium, strontium, barium, iron, mercury, hafnium, and zirconium on the method was investigated. Optical and Crystallographic Properties of Levulose Hydrates. FRANCIS T . JOSES,Kestern Regional Research Laboratory, Albany, Calif. During t h e investigation of the freezing preservation of foods two crystalline hydrates of levulose have been discovered. T h e optical and crystallographic properties of both these hydrates (the dihydrate and the hemihydrate) were determined and reported. Photomicrographs were used to show the character of the crystals in comparison with anhydrous levulose. The phase relations were shown in order to indicate the conditions under which each hydrate is formed, and t h e range in which each is stable. Levulose dihydrate is orthorhombic in prismatic crystals whose melting point is 21.3' C. The refractive indices are: 01 = 1.506, fl = 1.522, and y = 1.544. T h e optical axial angle (calculated) 2E = 156' and the optical character is (f). Levulose hemihydrate is hexagonal in slender needles. T h e refractive indices are: epsilon = 1.542, omega = 1.536. T h e optical character is ( f ) .

Chemical Institute of Canada A

T THE technical sessions of t h e 35th a n n u a l conference of the

Chemical I n s t i t u t e of C a n a d a , held in X o n t r e a l , C a n a d a , J u n e 2 to 4, 1952, t h e following papers u-ere presented before t h e Analytical Chemistry Division:

Colorimetric Determination of Ruthenium with P-NitrosodimethylUniversity of aniline. IT. A. E. MCBRYDE. ~ N D ALICE FISCHEL, Toronto. An aqueous solution of p-nitrosodimethylaniline, when heated with a solution of ruthenium chloride, buffered to p H 4, produces a bottle green-colored solution. This reaction has been found satisfactory as t h e basis for a colorimetric determination of ruthenium. The colored solution is stable for several days. Maximum absorption for the colored solution occurs a t 630 m p , and a t this wave length the reagent blank shows only a very small absorption. The sensitivity of the recommended colorimetric procedure is about 0.0025 microgram per sq. cm. per 0.001 extinction; this is more t h a n twice as sensitive as t h e rubeanic acid procedure and from six t o nine times as sensitive as procedures utilizing thiourea. Interference from other platinum metals is avoided by conventional distillation procedures, and the efficacy of various receiving solutions for this operation has been eramined. -4similar colored solution is obtained with p-nitrosodiethylaniline, but the reagent solution is not so convenient to prepare or so stable. This investigation was initiated some years ago by F. E. Beamish and his students. Microdetermination of Cobalt by the 1-Nitroso-2-naphthol Method.

W. E. NICHOL.

.Ifaster, accurate method for determining traces of cobalt is needed. Of older methods, t h e o-nitrosocresol method is apparently favored on this continent. I t is not short and as t h e cobalt complex has maximum absorption in the near ultraviolet, t h e use of a spectrophotometer is almost essential. I n contrast, the 1-nitroso-2-naphthol method can be used with ordinary colorimeters. E. Paulais in 1946 outlined a method using 1-nitroso-2-naphthol. His chief interference, ferric iron, is not removed but complexed with phosphate. Two precipitations of cobalt, the first of which takes 24 hours, removal of complexes of copper, nickel, and ferrous iron on a column of alumina, etc., make t h e process long. T h e author's studies show t h a t removal of the bulk of the iron in acid medium before t h e addition of 1-nitroso-2-naphthol makes one precipitation of cobalt sufficient. These operations require about 2 hours. A hydrochloric acid wash of the carbon tetrachloride extract eliminates complexes of other metals. When using a spectrophotometer the method has the same order of accuracy as the o-nitrosocresol method. I t is more rapid, necessary reagents are more quickly prepared, t h e complexing reagent is more stable, and the blank is more constant t h a n in the o-nitrosocresol method. Tables of comparative determinations by both methods were given.

A Micromolecular Still.

R. P. 9. SIMS.

d micromolecular still has been developed in which one drop oi'a sample of polymerized oil can be separated quantitatively into fractions and the molecular weight of the fractions determined simultaneously. The distilland, dispersed finely on a glass wool pad, i3 suspended from the end of a quartz spiral in the longitudinal axis of a n internal heating coil. T h e course of the distillation, which is conducted a t a pressure of mm., is followed by measuring with a cathetometer the changes in the extension of the quartz spiral. I n this apparatus, monomeric, dimeric, and trimeric methyl esters of f a t t y acids and monomeric and dimeric triglycerides have been distilled. Through prior calibration with pure materials, the molecular weight of the material can be estimated from the temperature a t which the distillation is taking place. While this still has been used principally with oils and fatty esters, it has been used successfully w-ith other series of compounds. Quantitative Organic Analysis via Functional Groups. S. SIGGIA, General Aniline & Film Corp. ilppiicability of this type of analysis to the needs of t h e organic analyst. Fundamental principles involved in choosing reactions to be used for the analyses and how these principles are applied. Problems t h a t can arise when using a certain reaction and how these problems are overcome or circumvented : Reaction completeness. Equilibrium. Solvent and titration problems (discussion of nonaqueous titrations). Interferences: (1) avoiding separation of components, (2) separating components (distillation, extraction, precipitation. dialysis, electrodialysis, chromatographic absorption, electrophoresis). Identification techniques using quantitatire functional group analysis. Routine Control Analyses for Sulfur Content of Heavy Hydrocarbons. S . ,4.S H E P P ~ R D . The need for a more rapid method than ASTM D 129-50 for t h e routine determination of sulfur in heavy hydrocarbons led t o t h e application of the Dietert high temperacure sulfur determinator, which w-as originally designed for t h e routine testing of sulfur in iron and steel samples. I n the method devised, sulfur is quantitatively oxidized t o sulfur dioxide from a boat placed in a high temperature furnace (2400" F.) in a stream of oxygen. T h e sulfur dioxide product is quantitatively absorbed in an ASTM lamp sulfur absorber containing hydrochloric acid-starch-iodide solution and directly titrated R7ith stoichiometric potassium iodate solution to a permanent blue end point. Alundum combustion boat lining is used to cover the sample and use of a filter plug in the combustion tube is eliminated. Sulfur may be determined with an accuracy a t least comparable to t h a t obtained by ASTM D 129-50 on a wide variety of heavy hydrocarbons including furnace fuel, diesel fuel, bunker fuel, lubricating oil, additive concentrates, t a r , and crude oil, without interference from most common elements. A single determination may be completed in 12 minutes and over 30 samples have been run by one operator in an 8-hour day.

V O L U M E 2 4 , NO. 7, J U L Y 1 9 5 2

1231

Some Examples of Combined Analysis by M a s s Spectrometry and gation into t h e composition of t h e strong phosphoric acids-acids Infrared Spectrometry in the Petrochemical Field. H. V. FULLERTON, containing more t h a n 72,4% by weight of PnOa-has been comG. S. TURNER,AND J. D . SANDS. menced. A metaphosphate glass has shown a n interesting chromatographic Complex petrochemical streams can be analyzed by applying both pattern. infrared and mass spectrometry t o samples prepared by low-temperature distillation or chemical isolation procedures. Three special analyses were described which illustrate the potentialities of such combined methods in multicomponent analysis. T h e first example is a complete analysis of the product stream from a butene dehydrogenation reactor. Hydrogen, carbon monoxide, carbon dioxide, and 17 hydrocarbon components were determined by T THE 3ith ordinary meeting of the Physical M e t h o d s G r o u p mass spectrometry. The distribution of butene isomers was deterof t h e Society of Public Analysts a n d O t h e r Analytical mined by infrared spectrometry after low-temperature fractionation. Cheniists, held M a y 16 at University College, Swaneea, E n g l a n d , T h e method is now being developed for routine use in evaluating catalyst performance. the follon-ing papers were presented. T h e second example is a survey for allenes and a-acetylenes in butadiene monomer recovered from a butadiene-styrene copolyTheory of Ion Exchange. C. W. DAVIES. merization process. Prior t o combined analysis, distillation was used T h e “strong” ion exchange resins are porous polyelectrolytes cont o concentrate individual allenes, and t h e silver acetylide method taining ions which exchange rapidly with ions of the same sign in an was used to isolate the total a-acetylenes. added solution. B y using a column procedure such exchanges may T h e third example is a study of all detectable impurities in a rebe made quantitative. There are also “weak” exchangers, which corered isoprene stream. Three distillation fractions --ere analyzed, absorb acid or alkali, and other special types are being developed. also a sample from which conjugated diolefins were removed by T h e kinds of exchanger nom commercially available were briefly maleic anhydride scrubbing. Sixteen hydrocarbons and chlorinated described, and their characteristics and physical chemistry outlined. organics were detected in concentrations of over 0.05 mole 70,and T h e best-known uses of exchange resins are for deionization t o give upper limits of concentration Tvere established for over 30 other comwater of much lower electrolyte content t h a n distilled water, and t h e ponents. separation of closely similar substances-e.g. rare earths, amino acids. I n this field they have t h e selectivity of other chromatographic abImportance of Analytical Control in the Manufacture of Vitamin sorbents combined with a higher capacity. T h e factors exploited in Products. J. A. CAMPBELL. such separation were summarized. Other uses of interest in analysis include quantitative exchange .k systematic survey of \.itamin products manufactured or dis(sodium by hydrogen), followed by titration; separation of intertrihuted in Canada has been undertaken hy t h e Vitamin and h-utrifering ions (calcium and phosphate) : collection and concentration of tion Laboratory of t h e Food and Drug Divisions to determine how trace constituents: absorption of gases; separation of large from closely they conform to label claim. All vitamin products of each small ions by a “molecular sieve” effect; and separation of electrolytes manufacturer have been analyzed for t h e vitamins claimed on t h e from nonelectrolytes. label. Results obtained to date indicate t h a t there are striking differences Some Newer Applications and Techniques of Cation and Anion between the potency of products manufactured under the supervision Exchange Resins in Chemical Analysis. G. H . OSBORS. of a control laboratory and those which are produced where no analytical control facilities are available. D a t a on individual vitamins conT h e present state of knowledge regarding t h e use of ion exchange tained in t h e preparations indicate t h a t there are particular problems resins in analysis was briefly reviewed and details were given of many which may be encountered in certain types of products. new applications which had been developed in recent months in the T h e d a t a emphasize t h a t t h e only effective means of controlling t h e laboratories of t h e author b u t which had not yet appeared in print. potency of vitamin products is by analysis of the final product before it is released for sale and a t intervals during its normal shelf life. Determination of Individual Rare Earths by Radioactivation Using Ion Exchange Separation. F. W. CORNISH. Polarographic Determination of Aluminum. R . P. GRAHAM AND J. .a. PAGE. T h e method consists of comparing t h e neutron-induced radioactivi t y of t h e rare earths in a sample with t h a t of standards, t h e activity T h e direct polarographic determination of aluminum is rendered of both arising from t h e same total neutron bombardment in t h e difficult by its relatively high discharge potential, by t h e problem of Harwell pile. After irradiation t h e sample is dissolved and after addihydrogen discharge, and by other factors. These problems were distion of carrier t h e rare earths are separated as a group-e.g., by precu5hed and means of coping with the difficulties were considered. cipitation as hydroxide, fluoride. and oxalate. T h e separation of the A procedure for the direct polarographic determination of aluminum individual rare earths is then carried out using a 115 X 0.6 em. column u-ah debcribed which involves a supporting electrolyte of magnesium of Zeokarb 225 with 0.23 -11 citrate as elutrient a t 100’ C. T h e chloride and sodium sulfate a t a controlled p H . T h e successful apcourse of t h e separation is followed by studying t h e radioactivity of plication of the method to t h e analysis of zinc-base die-casting alloys t h e eluate as a function of volume. Individual rare earths show up as was demonstrated. T h e method should be adaptable t o a wide variety peaks on a recorder chart and t h e activity of suitable portions of t h e of hubstances. collected fractions can be compared with t h a t of known weights of t h e corresponding standard. Identification is confirmed by decay Filter Paper Chromatography of Condensed Phosphates and Phosand energy measurements. phoric Acid. d.E. R . FTESTMAN. A. E. SCOTT, A N D JOAN T. PEDLEY.

Society of Public Analysts

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T h e study of t h e condensed phosphates and their corresponding arids has been handicapped t o d a t e by lack of adequate analytical methods. T h e chemical similarity of these compounds along with their tendency t,o revert t o t h e stable orthophosphate configuration makes them very difficult t o separate and identify. Filter paper chromatography has been used t o effect a separation and identification of t h e orthophosphate ( P O 3 ---, pyrophosphate (P207)---, triphosphate (PsOio)----- , trimetaphosphate (POa)--and tetrametaphosphate (Po3)---- anions. Since the sodium salts of t h e condensed phosphoric acids have been the most extensively studied, they h a r e been used in this investigation. Good qualitative results have been obtained and a quantitative method is being developed. T h e existence of t h e tetraphosphate anion (PaOlr)------, a subject of contention in t h e literature, has been confirmed, and a sample of sodium tetraphosphate prepared by hydrolysis of sodium tetrametaphosphate followed by a chromatographic separation using a cellulose column. Certain properties of sodium tetraphosphate have been investigated. T h e hydration of phosphoric anhydride has been followed chromatographically and the intermediate stages identified. An investi-

American Society for Testing Materials. Annual Meeting. Hotel Statler, New York, N. Y., June 23 t o 27 International Congress on Analytical Chemistry. Oxford, England, September 4 t o 9 Sixth Annual Symposium on Modern Methods of Analytical Chemistry. Louisiana State Cniversity, Baton Rouge, La., February 2 t o 6, 1953 Sixth Annual Summer Symposium. Rensselaer Polytechnic Institute, Troy, N. Y.. June 1953