I N D U S T R I A L S N D ENGINEERING CHEMISTRY
August, 11924
837
T h e Distillation Method of Separating Selenium from Tellurium' By Victor Lenher and D. P. Smith UNIVERSITY OR WISCONSIN, MADISON, WIS.
I
N HIS "Standard h4ethods of Chemical Analysis" Scott
is now heated by means of a Bunsen burner. The temperature is sufficiently controlled by observation of the sulfuric acid in the distilling flask. The acid is a t the correct temperature, 300" to 330" C., when slight fumes of sulfur trioxide are evolved. The flame of the burner is then reduced a little and the distillation continued until all the selenium has distilled over, which ordinarily requires 3 to 4 hours. The distilled selenium is collected in the receiver bottles and is determined after transferring to a beaker and passing sulfur dioxide into the solution a t a temperature of 15" to 22" C. Red elementary selenium is precipitated from this strong hydrochloric acid solution. The precipitate is allowed to settle and is washed by decantation with cold water several times. Hot water is then poured on the precipitate in the beaker, when the red selenium is transformed into the gray, granular variety, which is brought on a Gooch crucible, washed with alcohol, dried at 105" C., and * APPARATUS AND PROCEDURE weighed. The tellurium solution remaining in the distilThe apparatus found to be the simplest and to give the ling flask is poured into water and diluted with sufficient most accurate results is shown in the figure. It consists of a water so that the content of free sulfuric acid is less than 150-cc. Pyrex distilling flask, A , with a glass tube, B, sealed 25 per cent. Enough hydrochloric acid is added to make the in the top of the neck and extending to within 7 mm. of the solution 7 per cent acid. The tellurium is precipitated from bottom of the flask. The condenser tube, C, is sealed di- this solution by means of sulfur dioxide and hydrazine hydrorectly in the neck of the flask as close to the top as possible. chloride according to the method of Lenher and Homberger.2 The most important details of the apparatus are in the conThe receiver consists of three Drexel wash bottles, DI, Dz,D3, sealed together and connected to the end of the condenser struction of the flask A. It is necessary that the tube B by means of a ground-glass joint. These bottles at the be- should join the top of the flask as close to the exit of the condenser tube C as possible. Should any great distance separate these junctions, selenium tetrachloride will condense in the solid form and will not be driven over into the condenser. The sulfur trioxide fumes must rise to the top of the flask so that the hydrochloric acid gas may sweep all the selenium chloride vapors out of the flask into the condenser and receiver. RESULTS The method is accurate for either high or low amounts of selenium or tellurium. Good results are obtained with varying ratios of selenium and tellurium. The selenium and tellurium-containing material can be introduced into the flask in various combinations, but obviously hydrochloric or sulfuric acid solutions are the most desirable. Table I gives a series of figures obtained from various selenium and tellurium-containing mixtures.
describes a method that he has developed for separating selenium from tellurium by distillation. The method has been given considerable study by the writers, and inasmuch as the chemical literature contains little reference to it a few important details are herein described. This method is based on the volatility of selenium chloride from sulfuric acid solution when treated with hydrochloric acid gas? while tellurium chloride is nonvolatile under the same conditions. Scott's distillation method offers distinct advantages over other separations of selenium from the various metals in that none of the common elements naturally associated with selenium form volatile chlorides under the conditions of the experiment. Further, the selenium when distilled is collected in hydrochloric acid solution, from which it can be readily precipitated.
FIG.I
ginning of the determination are half full of distilled water. The saniple of selenium and tellurium-containing material is introduced into the flask through the tube B. The sample is washed down with enough sulfuric acid, specific gravity 1.84, to bring the volume of the solution to about 60 cc. Hydrochloric acid gas is now introduced from the generator E through the tube B. The generator consists of a 3liter flask into which, by means of a dropping funnel, concentrated sulfuric acid is introduced into concentrated hydrochloric wid. F1 and Fz are wash bottles containing concentrated sulfuric acid; Fa is an empty bottle. The flask A 1
Received May 26, 1924.
TABLEI (Figures are in grams) ,------SELENIUM---------TELLURIUM-----Expt. Taken Found Error Taken Found 0.1378 + O . 0004 0.1039 0.1048 1 0.1374 0.1378 + O . 0004 0,1039 0.1040 2 0,1374 + O . 0004 0,1039 3 0,1374 0.1378 0.1037 0.1039 +o. 0002 0.1044 4 0,1374 0.1376 0.0000 0,1374 0,1039 0.1040 0.1374
x 7
8 9 10 11
12
13 14
0,1374 0.2748
0,2748 0.2748 0.4166 0.4166
0.0687 0,0687 0.0687
0.1376 0.2748 0.2747 0.2762 0.4164 0.4162 0.0688 0.0684
0.0693
* J . A m . Chem. SOC.,SO,
+ o . 0002
0.0000 -0.0001 + O . 0004 - 0,0002 - 0,0004
+0.0001 +0.0003 t0.0006
387 (1908)
0.1039 0.0519 0,0619 0.0519 0 0619 0,0519 0.2074
0.2074 0.2074
0.1044 0,0521 0 0520 0.0520 0.0520 0.0522 0,2074 ~
0.2077 0.2077
Error +O. +O. -0. +O. +O. +O.
t-0. +O. +O. +O. +O.
0.
+O. +O.
I N D U S T R I A L A N D ENGINEERING C H E X I X T R Y
838
The following figures showing results obtained by the distillation method with anode slimes are identical with those obtained by Skowronski3using the Keller method: Selenium Per cent
8
7.01 7.09 7.10 J . A m Chem. Soc , 19, 771 (1897).
Vol. 16, No. 8
The results obtained by the distillation method with metallic copper are identical with those found by Skowronski using the Keller method.
Tellurium Per cent
Selenium Per cent
4.29 4.28 4.30
0.02 0.03
Tellurium Per cent
Less than 0.01
Properties and Structure of Some Alloys of AluminiumCopper-Tellurium'" By F. T. Sisco and M. R. Whitmore AIR SERVICE, WARDEPARTMENT, McCoox FIELD,DAYTON, OHIO
D
The wort described here is the result of an exploratory inoestigatelluride of aluminium and URING a research tion on the alloys of aluminium containing 5 per cent copper to which rise to the top of the metal on the light alloys as It Was decided, tellurium has been added in amounts wrying from 0.25 to 5.00 per of aluminium, the MetallUrgiCal B r a n c h , cent. Following a briefdescription of foundry practice, the physical however, to verify this SUSMaterial Section, of the Enproperties of these alloys and the eflect of tellurium on the microPicion and in addition, structure of aluminium are discussed. A method of analysis for gineering Division, Air Sershould tellurium be insoluble, to discover what deoxivice, decided to investigate the al/oys is giden. the effects of some of the dizing or degasifying effect, rarer elements on the propif any, the metal might have erties of aluminium containing 5 per cent copper. on the molten aluminium. Consequently, the alloys of the Owing to the large amount of work necessary to investigate composition noted in Table I were mixed and melted. completely the physical properties and microstructure of the FOUNDRY PRACTICE alloys as cast and after a variety of heat treatments, it was The metals were melted in a No. 20 Plumbago crucible in considered advisable to conduct a few experiments in the nature of an exploration and from the results of this explora- i'donarch oil-fired furnace. A total melt Of 10 to 12 Pounds tory investigation to decide whether the series of alloys would was made in each instance. The aluminium was used in the form of notched bars; the copper was added in the form of be worth an extensive research. a 50:50 hardener containing 50 per cent each of copper and MATERIAL aluminium and only traces of impurities. (A 50: 50 copperThe alloys used in the investigation are shown in Table I. aluminium hardener is made by melting copper and alum&m The compositions noted here are as mixed before melting. in separate furnaces and mixing the metals. Owing to the exothermic reaction when molten copper is added to molten TABLE I-PERCENTAGE COMPOSITION OF ALLOYS A S MIXED aluminium, about half the aluminium is melted, the reMelt Aluminium Copper Tellurium mainder being added in the form of bars to avoid an extreme 5.00 0.25 1 94.75 5.00 0.50 94.50 2 rise in temperature. After mixing, the metal is poured into 5.00 0.75 a 94.25 small ingots.) 5.00 1.00 94,OO 4 5.00 2.00 93.00 5 The aluminium and the copper-aluminium hardener were 5.00 3.00 92.00 6 5.00 4.00 91.00 charged into the crucible and melted as rapidly as possible. 5.00 5.00 90.00 A8 A Although a very accurate temperature control of melting was 5,OO None 95.00 5.00 None 95.00 8B not necessary, it was kept between 1350" and 1400" F. As 0.07 XC None 99.820 soon as the alloy was melted, the temperature was taken a This is the pure alumin~umused as the basis for all the alloys. (with a bare chromel-alumel thermocouple and a potentiomI n order to have conditions as nearly ideal as possible the eter) and the crucible removed from the furnace. purest commercial aluminium and copper were used. The The tellurium was now added, being poled well below the analysis of these materials is as follows: surface, and the melt stirred thoroughly. The melted alloy Si Cu Fe A1 was then brought to the pouring temperature, 1300" F., Aluminium 0 04 0 07 0 07 99 82 which temperature within a 10-degree range was maintained Copper .. 99 94 .. .. for all the melts. As soon as the metal was a t the desired The tellurium used was the pure metal purchased from temperature, the test bars were cast. Three sets of TB-1 the manufacturer. test bars were cast in green sand from each melt. Metals of high purity were used in order to prevent the The TB-1 test bar, which is the standard of the Air Serappreciable amounts of silicon and iron occurring in ordinary vice for sand-cast aluminium alloys, is shown in Fig. 1. The aluminium from influencing the physical results. By melting central bar of the three is designated B; either of the outside metals of a very high purity, any appreciable change in physi- bars is then designated A or C. cal properties would be due to the different amounts of tellura Private communication, S. Skowronski, research chemist, Raritan Copper Works, Perth Amboy, N. J., May 24, 1923. Skowronski stated, ium. It was suspected early in the work that tellurium would "in five meltings, the maximum amount of tellurium that could be found in aluminium was 0.32per cent.* * * Aluminium telluride decomposes with not dissglve in molten aluminium, but rather would form the the water, giving o f f hydrogen telluride, which is readily recognized owing to its
-
1 2
Received March 22, 1924. Published by permission of Chief of Air Service, War Department.
fetid odor, which you will promptly notice if you put any residue or slag from your alloy in water."
