GERMAXIUM. XX1II.l GERMANIUM MONOSULPHIDE BY L. M. DENNIS AND S . M. JOSEPH
Germanium monosulphide was first prepared2 by Clemens Winkler by heating a mixture of germanium disulphide and metallic germanium in a current of carbon dioxide, and also by heating germanium disulphide in a current of hydrogen. I n the latter reaction Winkler states that the temperature was carried to "moderate glowing" and he adds that the germanium monosulphide is reduced to metallic germanium at higher temperature. The present investigation was undertaken to ascertain the optimum conditions for the preparation of germanium monosulphide by heating the disulphide in hydrogen. Sixty grams of germanium dioxide were converted into germanium disulphide by heating the dioxide with hydrochloric acid through which a current of hydrogen chloride was passed, and precipitating the distillate of germanium tetrachloride with hydrogen sulphide. The dry germanium disulphide was placed in porcelain boats which were heated in a combustion tube in an electric furnace in acurrentof dry hydrogen that had been carefully freed from oxygen. Provision was made for testing the escaping gas from time to time for hydrogen sulphide. The temperatures were measured with a thermometer placed within the combustion tube. The changes noted in successive experiments were as follows: Experiment I : C.-No change. I 50' C.-Some moisture from the not thoroughly dry germanium disulphide condensed in the cooler parts of the tube. 200' C.-White germanium disulphide darkened somewhat. First trace of hydrogen sulphide detected in the escaping gas. 250' C.-Powder took on yellowish tinge. Stronger test for hydrogen sulphide. 300' C.-Powder was now distinctly yellow. Strong test for hydrogen sulphide. 350' C.-Powder continued to darken. 375' C.-Reduction continued. 400' C.-Powder was now orange-yellow. 410~-41s~ C.-Powder turned brown or brownish black. Still strong test for hydrogen sulphide. The temperature was kept constant at this point. Crystals appeared on the side of the tube above the boats, some brown, some black, and some with a bluish luster. 100'
Contribution from the Department of Chemistry, Cornel1 Vniversity. *Winkler: J. prakt. Chem., 142, (N. S. 34) z ~ (1886.) j
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Upon completion of the first run, the resulting material was found to be composed of two distinct types of material, one being brownish, and the other black. Examination of the black substance under the microscope showed the presence of large, opaque crystals. These were insoluble in mineral acids. A second run was made, using more of the germanium disulphide and heating it to a slightly higher temperature. Experzment 11: 415' C.-)laterial turned to brown and black as before. 420-430' C.-Reduction continued and more of the black, crystalline material
was obtained. I n this run the temperature was kept between the limits 41oO-430~ C. At about 420°, a metallic glint, resembling that of galena, appeared on the walls of the tube. This second experiment produced a material which showed very little of the brownish substance of the first run, and contained a larger percentage of the black, crystalline product. A third experiment was carried out at still higher temperatures. Experanzent 111: 440' C.-Black, crystalline substance formed in large amounts. Glistening particles formed on the glass above the boat. 450-480' C.-Temperature was maintained within this range. Black glistening particles continued to sublime in increasing quantities on the walls of the tube. These were in the forms of long, needle-like crystals and thin tablets, showing a luster like galena. I t is thus established that the optimum temperature for the reduction of germanium monosulphide lies at about 480' C. Analysis.-The analysis of the crystalline germanium monosulphide offered difficulties because of the resistance of the substance to the action of solvents. Several different methods were tried with not wholly satisfactory results and finally for the purpose of identifying the compound, the sulphur was determined by combustion in oxygen, the sulphur dioxide being absorbed by a solution of potassium carbonate to which bromine had been added, In the first experiment all of the sample was placed in one boat and when the temperature of the tube reached 800' oxidation took place with considerable violence, and the sulphur dioxide was set free in so large volume as to draw back the solution of potassium carbonate into the combustion tube. This difficulty was avoided by placing small portions of the sample in a series of small porcelain boats in the combustion tube and using a gas combustion furnace, heating one boat at a time. The results of the analysis were as follows: Substance = 0.8733. Wt. of BaSOI = 1.9084 = 0.2621 S = 30.01 percent. S. The calculated percentage of sulphur in GeS is 30.63. I t was evident that some of the sulphur still remained in the residue in the boats. This was extracted by a digestion of the boats with their contents in concentrated hydrochloric acid to which 30 per cent. hydrogen peroxide was added from time
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to time. From the solution thus obtained an amount of barium sulphate corresponding to 0.00472 gram of sulphur was precipitated. This represents 0.54 per cent. of sulphur in the compound, giving the total sulphur found by analysis 30.55 per cent. which agrees fairly well with the calculated percentage, 3 0 . 6 3 . Propertaes of Crystalline Germanium Monosu1phzde.-Very hard, black opaque crystals which are practically insoluble in mineral acids. They are dissolved by fusion with potassium hydroxide and by long digestion with an aqueous solution of potassium hydroxide. When this solution is acidified a reddish brown precipitate of germanous sulphide resulted. Professor C. W. Mason kindly examined the crystalline product under the microscope and reported as follows:“Thin tablets, with graphitic luster. Bevelled rectangles with truncated corners. Thinnest flakes and fragments show dark brownish-red to straw by transmitted light, with distinct pleochroism. More opaque than hematite. Probably less than one micron thick to show transmission color. Crystals probably rhombic bi-pyramidal, like tin monosulphide. Faces 010, 1001, 001, 101,110 present. Terminalanglesof tablets IOZ’.’’
Summary The method of preparing germanium monosulphide by heating germanium disulphide in hydrogen as proposed by Winkler was studied, and the conditions for the preparation of crystalline black germanium monosulphide with the avoidance of the separation of metallic germanium were ascertained. The identity of the product was established by analysis, and some of its chemical and physical characteristics are described. Ithaea. Xeic Y o r h
