INDUSTRIAL AND ENGINEERING CHEMISTRY
8
methods differ considerably. The Raman effect has a definite advantage over infrared spectroscopy in being able to study materials in water solutions; but in the general organic field the infrared method is by far the more practicable. Important disadvantages of the Raman method are: (1) the necessity of refining each sample to remove ever-present traces of impurities which fluoresce, masking the spectra; (2) the long exposure times and general difficulty of producing spectra suitable to be microphotometered; and (3) the insensitivity of the method to compounds in small concentrations. Advantages of analysis b y means of infrared spectroscopy include the following: The amount of sample required is very small; no preliminary refinement of the sample is needed; and the method is sensitive to small concentrations, is accurately quantitative, and requires a very short time for a complete analysis.
Acknowledgment The writer is indebted to J. D. Hanawalt for many valuGildart for very able assistance able suggestions and to L’ in the laboratory.
Vol. 13, No. 1
Literature Cited Barnes, R. B., Bonner, L. G., and Condon, E. U.,J. Chem. Phys., 4, 772 (1936). Coblenta, W. W.,“Investigations of Infrared Spectra”, Pub. 35, Carnegie Institution of Washington, 1905. Dennison, D. M., Rev. Modern Phys., 3, 280 (1931). Gershinowita, H., and Wilson, E. B., J. Chem. Phys., 6 , 197
(1938). Gildart, L. W., and Wright, Norman, to be published in Rev. Sci. Instruments. Hanawalt, J. D., and Rinn, H. W., IXD. ENO.CEEM.,Anal. Ed., 8,244 (1936). Hanawalt, J. D., Rinn, H. W., and Frevel, L. K., Ibid., 10,457 (1938). Lecomte, Jean, “Le spectre infrarouge”, Paris, Presses Universitaires de France, 1928. McAlister, E. D., Phys. Rev., 49, 704 (1936). Pfund, A. H., Rev. Sci. Instruments, 8,417(1937). Pfund, A. H., Science, 90, 326 (1939). Schaefer, C.,and Matossi, F., “Das Ultrarote Spektrum”, Berlin, Julius Springer, 1930. (13) Strong, J., and Randall, H. M., Rev. Sci. Instruments, 2, 586 (1931). PRESENTED before t h e Division of Industrial and Engineering Chemistry a t the 100th Meeting of the American Chemical Society, Detroit. Mich.
Rapid Determination of Antimony, Tin, and Bismuth SILVE KALL3IANN
AND
FRANK PRISTERA, Walker and Whyte, Inc., 4.09 Pearl St., New York, N. Y.
New short methods for the accurate determination of antimony, tin, and bismuth in metals, alloys, and ores are described. Antimony, tin, and bismuth are coprecipitated with manganese dioxide formed by the reaction of manganese ion and potassium permanganate in hot dilute nitric or sulfuric acid solution. For the determination of antimony, tin, or both, the manganese dioxide precipitate is fumed with sulfuric acid, potassium hydrogen sulfate, and ammonium sulfate. To determine antimony the solution is diluted with sulfur dioxide water, boiled dow-n with hydrochloric acid, diluted, and titrated with potassium permanganate or potassium
B
L U M E N T H A L ( I ) devised the coprecipitation of antimony with manganese dioxide by the reaction of manganous ion and potassium permanganate in hot dilute nitric or sulfuric acid solution. He states that tin and bismuth are also quantitatively precipitated, whereas arsenic comes down incompletely, and lead and copper are precipitated only in traces. Blumenthal confines the application of his method to the determination of antimony in copper. The authors have elaborated a considerably shorter method by omitting the removal of certain contaminations of the manganese dioxide precipitate. Many useful and time-saving applications are possible, facilitating considerably the determination of antimony, tin, and bismuth in various metals, alloys, and ores. DETERMINATION OF ANTIMONY.A reliable and a t the same time fast determination of antimony in blister copper has been investigated by the authors. The methods of Jungfer (16) and Hampe (16), who remove the copper as cuprous iodide and thiocyanate, respectively, are very lengthy, involved, and too expensive for routine work. The method proposed by Evan (Q),who separates the copper with sodium hypophosphite, has the same disadvantages. The
bromate. Tin is determined by reducing with nickel and hydrochloric acid the solution containing the fumed manganese dioxide precipitate, or the solution that remains after the titration of the antimony, and finally titrating with standard iodine solution. For the determination of bismuth the manganese dioxide precipitate is dissolved in dilute nitric acid and hydrogen peroxide. The bismuth is separated with the help of zinc oxide, w-hich precipitates the bismuth as basic nitrate. This in turn is dissolved in nitric acid, from which the bismuth is finally precipitated and weighed as bismuth oxychloride.
coprecipitation of antimony oxide with metastannic acid, as described by Scott (25),is applicable only in the presence of large amounts of tin and is unreliable when iron is present, as stated by Classen (6). The method involving the principle of coprecipitating antimony with ferric hydroxide, advocated by Brownson ( d ) , is too controversial to be considered a good standard method. Blumenthal’s method ( I ) , though unquestionably correct, as confirmed by Park and Lewis (22), and having many advantages over any of the methods mentioned above, is too lengthy for routine work. [Brownson’s method is criticized adversely by Blumenthal (1, g), who claims that antimony comes down only incompletely, and favorably by Boehm and Raetsch (S).] This paper presents a very accurate method, so rapid that it requires no more than 3 to 4 hours as compared to about 7 hours by Blumenthal’s method and more than one day by other methods. It has been successfully applied to various ores, making it possible to perform a n antimony determination in ores in about 5 hours, whereas any of the established standard methods for the determination of antimony in ores takes more than one day. DETERMINATION OF TIN. The authors show that determination of tin with the aid of the manganese dioxide coprecipi-
January 15, 1941
ANALYTICAL EDITION
tation is very useful, particularly when small amounts of tin must be separated from large quantities of copper, lead or silver which would either interfere or render a proper determination more difficult. A tin determination in blister copper takes about 4 hours and a simultaneous determination of tin and antimony requires about 5 hours. DETERhfINATION OF BISMUTH.I n separating bismuth from copper, lead, silver, and other impurities the authors have made use of the manganese dioxide coprecipitation. Where it is customary and advisable to scorify a certain amount of the sample [Craig ( 8 ) advocates scorification for the separation of bismuth from antimony and other impurities], the manganese dioxide precipitate is contaminated by only small amounts of lead. I n such cases the final procedure for the determination of bismuth as bismuth oxychloride has been considerably shortened by the authors by eliminating the customary sulfide, carbonate, and basic nitrate separations and substituting a new separation of bismuth from lead and manganese which is based upon the fact that zinc oxide precipitates bismuth as basic nitrate while lead and manganese stay in solution. The final bismuth oxychloride precipitate can be obtained in less than 6 hours.
Preparation and Solution of Sample I n dissolving the sample the following facts were kept in mind : The coprecipitation of antimony, tin, and bismuth Jvith manganese dioxide is best performed in nitric acid solution. A sulfuric acid solution was used by the authors for the determination of antimony and tin when previous decomposition of the sample with aqua regia was required and when the sample was free from or low in lead. The acidity is very important for the precipitation of the bismuth, because it should not exceed 0.07 N-that is, 1.5 ml. of concentrated nitric acid in 300 ml. of solution-otherwise precipitation of bismuth will be incomplete. The acidity may be as high as 0.5 iV without running the risk of losing antimony or tin. BULLION A N D ALLOYS OF COPPER, SILVER,LEAD,AXD ZISC. An adequate amount of the metal was dissolved in nitric acid, disregarding any undissolved oxides of antimony or tin. The solution was warmed t o expel any oxides of nitrogen and the acidity was adjusted. ORESAND CONCENTRATES. To determine antimony and tin in ores and concentrates, and bismuth in high-grade bismut'h ores, an adequate amount of bhe sample was fused with sodium peroxide in a nickel crucible. The fusion was leached with water and acidified with nitric acid. A little hydrogen peroxide was added if the solution did not become clear at this stage. Any silica or undissolved oxides of antimony or tin were disregarded. The excess of hydrogen peroxide was expelled and the acidity adjusted. To determine bismuth in low-grade bismuth ores (bismuth below 1 per cent), 2.5- to 5-gram portions of the sample were scorified with 65 grams of test lead. When t'he amount of bismuth was very low 2 to 4 of the lead buttons, which weighed about 25 grams, were combined, scorified again to about 25 grams, flattened, and dissolved in dilute nitric acid. The acidity was adjusted to 0.07 N .
Experimental Procedure To about 300 ml. of the carefully adjusted nitric or sulfuric acid solution containing not more than 300 mg. of antimony, tin, or bismuth, 5 ml. of about 5 per cent manganese sulfate solution were added. [In the presence of considerable amounts of lead and always for the determination of bismuth, instead of manganese sulfate a manganese nitrate solution of corresponding strength was used.] The solution was heated to boiling and 5 ml. of about 1 N potassium permanganate were added with the aid of a pipet. After boiling for about 3 minutes, 3 ml. more of the potassium permanganate solution were added. The solution was allowed t o simmer for 3 more minutes and then was filtered through a quick-running filter paper and washed twice with hot water. The filtrate was transferred into the original beaker, and
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3 ml. of 5 per cent manganese sulfate solution were added. The solution was brought to a boil, and the precipitation of manganese dioxide was repeated with 3 ml. of 1 N potassium permanganate solution. After boiling for about 3 minutes, the precipitate was filtered through the original paper and washed 8 to 10 times with hot water. DETERMINATION OF ASTIJIONY. The beaker was wiped with a small piece of paper moistened with sulfur dioxide water, This, together with the manganese dioxide precipitate and the filter paper, was placed in a 500-ml. Erlenmeyer flask, to which were added 3 grams of ammonium sulfate, 1 gram of potassium hydrogen sulfate, and 25 ml. of concentrated sulfuric acid. The precipitate was fumed on a hot plate, first cautiously and then lyith the full heat, until all the carbon was oxidized and the faint pink color of the manganese sulfate prevailed. This operation was performed very rapidly because of the oxidizing effect of the manganese dioxide. A little solid ammonium persulfate was added and the fuming continued over a bare flame for about 2 more minutes. After the solution had cooled, 75 ml. of sulfur dioxide water and 100 ml. of concentrated hydrochloric acid were added, and the solution was boiled down to about 85 ml. Sext, 200 ml. of cold water were added and the solution was cooled to below 15" C. and finally titrated with 0.1 N or weaker potassium permanganate solution. To carry out the tit,ration with potassium bromate, 120 ml. inst'ead of 100 ml. of concentrated hydrochloric acid were added, and the solution was boiled down t o about 100 ml., diluted with 100 ml. of hot water, and titrated using met,hyl orange as indicator.
+ 4KMn04 + 16H2SOa = 5Sbr(S04), + 2K2S04 + 4?.InSo4 + 16H20 3SbC1, + I
