Analvsis of Indium Allovs J
J
CHARLES W. HOPKINS Metals Research Laboratory, Carnegie Institute of Technology, Pittsburgh, Penna.
I
X' THE course of investigations conducted in the Metals Research Laboratory on binary indium alloys, it became necessary t o do considerable quantitative analyses in order to determine the percentages of the constituents present. As this work required the greatest accuracy consistent with a reasonable time factor per analysis, a thorough investigation of the methods available was conducted. A careful literature research revealed that very few accurate methods for analysis of indium alloys had been reported. Laboratory tests soon showed which of these could be depended upon t o give usable results. As i t was desired, in many cases, to have a fairly rapid means of determining the purified indium solution, a combination of several methods was worked out. I n general, the methods of alloy analysis reported by Moser and Siegmann (9) were found entirely satisfactory and could be utilized to prepare the indium solutions for the potentiometric titration method of Bray and Kirschman ( I ) , by means of which a rapid and reasonably accurate determination of indium could be obtained. Analyses of indium-lead, indium-zinc (8, 9), and indiumaluminum (9) alloys were accurate to 0.1 to 0.2 per cent, this degree of accuracy being highly reproducible. I n the case of indium-tin alloys, however, no usable method was found which could reproduce results to better than 1 per cent. All available procedures were investigated and several original ones tested b y the author, but as yet a high degree of accuracy for indium-tin determinations has not been found. The suggested separations of Nizhnik (IO)and Erametes (4), however, seem to offer the best methods for laboratory use. One of the greatest sources of error encountered in indium alloy analyses was that due to iron, particularly so where titration with potassium ferrocyanide was used (1, 6). Moser's (9) method for the removal of iron from indium solutions has proved entirely adequate and rapid, though the equally efficient procedures of Mathers (7) and Prichard (8) may be employed. Because of the increased interest in indium and indium alloys, i t is hoped that the methods outlined here will be of value to workers in this field.
Table I lists results of some typical analyses. INDIUM-ZINC ALLOYS. Dissolve a 0.1- ram sample of alloy in 25 cc. of concentrated hydrochloric acid dilute to 50 cc., and neutralize with concentrated ammonium hydroxide. Add 10 cc. of dioxygen solution and after a few minutes run in sufficient 10 per cent potassium cyanate to make it alkaline to methyl orange (yellow). Heat to boilin , iilter and wash coagulated indium hydroxide immediately. %ave d t r a t e and washings for zinc determination. Dissolve indium hydroxide in 15 cc. of 0.5 N hydrochloric acid and dilute to approximately 150 cc. For the best iron separation adjust to 0.03 N in hydrochloric acid, and then run in hydrogen sulfide while the solution is hot (90" (2.). Filter off ferrous sulfide and wash precipitate several times with ammonium sulfide soiution. Collect filtrate and washings, heat to remove excess hydro en sulfide, and then evaporate down to a small volume. Add hyfrochloric acid to dissolve indium sulfide precipitate, and dilute to 150 cc. Heat to about 60" C. and add 1 to 1 ammonium hydroxide to precipitate indium hydroxide. To determine gravimetrically, ignite indium hydroxide to indium oxide and weigh. For potentiometric titration with potassium ferrocyanide (1) dissolve indium hydroxide in 20 cc. of 0.1 N hydrochloric acid and dilute to 250 cc. To determine the zinc, collect filtrate and washings from the indium-zinc separation and add 10 cc. of hydrochloric acid. Place the solution on a hot plate and allow to boil until evaporated down approximately 50 per cent. Now remove it, dilute to 100 cc. with distilled water and precipitate zinc hydroxide with 1 to 1 ammonium hydroxide. Ignite zinc hydroxide and weigh as zinc oxide. INDIUM-ALUMINUM ALLOYS. Dissolve 0.1-gram sample in 1 to 1 hydrochloric acid, dilute to about 50 cc., and neutralize with ammonium carbonate after adding 2 grams of sulfosalicylic acid. Make the solution neutral to methyl orange and acidify with acetic acid (just slightly acid). The volume of the solution at this point should be between 125 and 150 cc. Run in hydrogen sulfide, filter off indium sulfide precipitate, and wash it, being careful to save all the filtrate and washings for the aluminum determination. Now dissolve indium sulfide precipitate in dilute hydrochloric acid, and dilute so as to adjust acidity to 0.03 N . Run hydro en sulfide into hot solution (90' C.) to precipitate ferrous sJfide, which is filtered off and washed with ammonium sulfide solution. Evaporate filtrate and washings containing indium down nearly to dryness on a hot plate and then add 10 cc. of 1 N hydrochloric acid to dissolve the indium sulfide. After solution is complete, add 50 cc. of distilled water and precipitate indium hydroxide with concentrated ammonium hydroxide, Filter off this precipitate, wash,
Procedures
TABLEI. TYPICAL ANALYSES
INDIUM-LEAD ALLoYa. Dissolve a 0.1-gram sample of alloy in 20 cc. of aqua regia, and salt out the major portion of the lead with absolute alcohol in an ice-salt bath. Filter off lead chloride, wash with 1 to 1 hydrochloric acid plus alcohol solution, and save for subsequent lead determination. Now collect filtrate and washings, evaporate to dryness, and dissolve residue in 10 cc. of 0.5 N hydrochloric acid. Dilute solution to 100 cc., run in hydrogen sulfide, and filter off lead sulfide. Wash with ammonium sulfide solution and add precipitate to lead chloride residue. Adjust acidity to 0.03 N with hydrochloric acid, heat to boiling, and run in hydrogen sulfide to precipitate iron sulfide. Filter and wash, collect filtrate and washings, and evaporate solution until all hydrogen sulfide is removed. Dissolve any precipitate with hydrochloric acid, then heat again. Precipitate indium hydroxide with concentrated ammonium hydroxide. To determine gravimetrically merely ignite indium hydroxide and weigh as indium trioxide. If the potentiometric titration with potassium ferrocyanide is used ( I ) , dissolve the indium hydroxide in 20 cc. of 0.1 N hydrochloric acid and dilute the solution to 250 cc. for titration. To determine lead in the alloy, convert lead sulfide to lead chloride, add to the first precipitate of lead chloride, and dissolve the entire amount in hot water. Add saturated potassium chromate solution to precipitate lead chromate which is dried and weighed as such.
Analysis
Sample Gram
Indium Present Gram
Lead Present Grana
Indium Found Gram
Lead Found Gram
A
0.1000 0.1000 0,1000 0,1000 0.1000 0,1000
0.0960 0,0960 0,0960 0,0798 0,0798 0,0798
0.0040 0.0040 0.0040 0.0202 0.0202 0.0202
0.09595 0.09597 0.09693 0,07975 0,07977 0,07977
0.0041 0,0039 0.0038 0.0203 0,0200 0.0201
B
C
D E F
Zinc Found
Zinc Present G
H I J
K L
0.1000 0.1000 0.1000 0.1000 0.1000 0.1000
0.0972 0.0972 0,0972 0.0754 0.0754 0,0754
0.0028 0.0028 0.0028 0.0246 0.0246 0.0246
0,09694 0.09716 0.09720 0.07837 0.07540 0.07538
Aluminum Found
Aluminum Present 0.1000 0.1000 0.1000 0.1000 0.1000 0.1000
638
0.0500 0.0500 0,0500 0,0600 0,0600 0.0600
0.0500 0.0500 0.0500 0.0400 0.0400 0.0400
0.0027 0.0024 0.0026 0,0244 0.0246 0.0242
0,0498 0.0498 0,0499 0,0599 0,0596 0.0898
0,0498 0,0499 0.0498 0.0398 0,0396 0,0399
ANALYTICAL EDITION
August 15, 1942
and ignite to indium oxide for gravimetric determination. For potentiometric titration, dissolve indium hydroxide in dilute hydrochloric acid and dilute the solution so that it is not more than 0.04 N in hydrochloric acid. Determine the aluminum in the usual way by precipitating aluminum hydroxide and igniting to aluminum oxide for weighing gravimetrically. INDIUM-TIN ALLOYS. Treat 0.1 to 0.2 gram of the alloy sample with concentrated nitric acid, and remove the major portion of the tin as metastannic acid. Dissolve this metastannic acid and reprecipitate t o assist removal of any occluded indium solution. Now add atrates and washings from both precipitations, precipitate indium as the hydroxide with 2 N sodium hydroxide (4, and then redissolve by addition of an excess. Boiling the solution, or addition of ammonium chloride causes reprecipitation of indium hydroxide; tin is not precipitated under these conditions. As this separation is not complete, neutralize the filtrate with hydrochloric acid and boil, causing 0.1 per cent of dissolved material to precipitate. Repeat this procedure two or three times for best separations. Repeated solution and reprecipitation of indium precipitate, however, still left more than 1 per cent of tin which could not be removed from the indium. Determine indium and tin aa the oxides. In attempting to locate a suitable means of separation of indium and tin for accurate quantitative analyses, many types of separation were studied and tested. The volumetric determination of tin (11) with iodine in the presence of indium gave poor results, as did the determination of indium potentiometrically with potassium after distillation of stannic chloride from indium solution. The precipitation of indium by means of 8-hydroxyquinoline (6) and also by 8-oxychinolate (3) likewise proved unsatisfactory.
Summary Available methods for indium alloy analysis were investigated and the most accurate and efficient chosen by means of analytical tests. For rapid determinations of indium, the
639
potentiometric titration of Bray and Kirschman using POtassium ferrocyanide was used. Satisfactory procedures for indium-lead, indium-zinc, and indium-aluminum were determined, but no precise method for indium-tin alloys could be found which permitted a determination of greater than 1 per cent accuracy. I n the case of indium-lead, indium-zinc, and indium-aluminum alloys, however, an accuracy of 0.1 to 0.2 per cent was attainable.
Acknowledgment The Bristol-Myers Company, New York, N. Y., and the Sun Tube Company, Hillside, N. J., have sponsored the research program of which this investigation is a part.
(1)
Literature Cited Bray, V. B., and Kirschman, H. D., J. Am. Chem.
SOC.,49,
2739-44 (1927). (2) Dennis, L. M., and Bridgman, J. A.,Ibid., 40, 1549 (1918). (3) Eineoke, E.,and Harms, J., Z. anal. Chem., 98, 429-46 (1934). (4) Erametsl, Olavi, Suomen Kemistilehti, 13B, 17-18 (1940). (5) Geilman, W., and Wrigge, F. W., Z. unorg. allgem. Chem., 209, 129-38 (1932). (6) Hope, H. B,, Skelly, J. F., and Ross, Madeline, IND. ENQ. CHEM.,ANAL.ED.,8, 51-2 (1936). (7) Mathers, F. C., J. Am. Chem. SOC.,30, 209 (1908). (8) Mathers, F. C.,and Prichard, C. E., PTOC. Indiana A d . Sei., 43,125-7 (1934). (9) Moser, Ludwig, and Siegmann, Friedrich, Monats. 55, 14-24 (1930).
(10) Nizhnik, 0.T., Zapiski Inst. Khim., Akud. Nauk U.S. 8.R.,6, NO. 3-4, 265-87 (1940). (11) Scott, W. W.,“Standard Methods of Chemical Analysis”, 5th ed., Vol. I, pp. 969-70,New York, D.Van Nostrand Co., 1939.
Viscosity Determination of Polymer Solutions D. W. YOUNG, Standard Oil Company of New Jersey, AND E. H. MCARDLE, Standard Oil Development C o . , Elizabeth, N. J.
A new set of bubble tubes extends the Gardner-Holdt series to viscosities of 1000 poises, and thus adapts this rapid method to the measurement of viscosities of high polymers in volatile solvents. The eleven tubes in the set are numbered from 1/2 to 10, and cover the range from 50 to 1000 poises in steps of 100. To minimize effect
I
h’ CONNECTION with recent work (2) requiring the
rapid and precise determination of polymer solution viscosities, the necessary accuracy was found obtainable with the Gardner-Holdt rising air bubble viscometer (1). Results are duplicable, since no solvent is lost, as in using the majority of other viscometers. Further, by inverting the standard tubes at their designated temperature (25’ C.) alongside a water bath maintained a t a different temperature, and containing the sample tubes arranged on a hinged mounting, it is possible to take measurements a t a series of temperatures with speed and with a n accuracy sufficient for most purposes. The highest viscosity available in a closely related GardnerHoldt series is the Z6 tube of the “heavy bodied series” (148
of temperature, each tube is filled with a mixture of a 105 viscosity-index lubricating oil and a polybutene of 12,000 molecular weight. Diameter of tubes is 21.3 mm., double that of the regular Gardner-Holdt series. Length is the same. These dimensions make for ease in filling, and save 80 per cent of the measuring time.
poises), and hence the choice of polymers and their solution concentrations was delimited a t that value. It was also found diffcult to fill sample tubes of 10.65-mm. inside diameter with highly viscous solutions of polymers in volatile solvents, without losing appreciable solvent. I n addition, were it attempted to extend the viscosity range with the small diameter tubes, the time of bubble ascent would become excessive (Figure 1). A series of four experimental tubes, of the same length (11.4 cm.) but of progressively larger diameter, was accordingly constructed from regular Pyrex tubing. Carefully made flat bottoms permitted standing perfectly upright on a horizontal surface, without the aid of a holder. Times of bubble
