G E R X I X I U M . XX.' PREPARATIOX OF FUSED GERRIAXIUM DIRECTLY GERRIAXIUM DIOXIDE? BY KATHARINA M . T R E S S L E R .4ND L . >f. DENNIS
Up to the present time, fused, massive germanium has been prepared by first reducing germanium dioxide by heating it in hydrogen and then fusing the residual powder under sodium chloride3 at a temperature of about IOOO". This reduction in hydrogen is a tedious and time-consuming process, and various attempts have been made in the Cornell Laboratory to shorten t'he procedure. Reduction with granular aluminum goes smoothly to completion, but there is heavy loss of germanium because of volatilization of the intermediate reduction product, germanous oxide. The same difficulty was encountered in experiments upon the electrolytic preparation of metallic germanium. Germanium dioxide dissolves readily in molten potassium fluogermanate, or in molten crj-olite, and the metal separates in small pellets upon electrolysis in a graphite cell with a graphite cathode. The yield, however, was low because of loss of germanous oxide. Since germanium apparently does not unite with carbon to form a ~ a r b i d e , ~ it was thought that it might be possible to reduce the dioxide with carbon under a layer of dry sodium chloride a t a temperature high enough to yield the metal in fused, massive form, and at the same time develop a technique which would permit of the recovery of any germanous oxide which might be volatilized during the reaction. Germanium dioxide and sugar carbon were intimately ground together and were then mixed with approximately an equal weight of pure sodium chloride. These charges were placed in special unglazed porcelain crucibles j cm. high and 3 cm. in diameter and were tamped down, the charge in each case filling the crucible about half full. The crucible was then filled t o the top with sodium chloride which was also tamped. I n the early experiments the crucible was heated by a gas-air blast lamp and was held a t a temperature of approximately 1000' for 30 minutes. The crucible was a t first covered !Expt. I ) but as there was some volatilization of germanous oxide, a large tube of hard glass was slipped over the top of the crucible, and air was drawn upward through this tube. Any germanous oxide which volatilized condensed in the tube either as such or as germanium dioxide formed through oxidation. The results of three runs by this method were as follows: ~~~
Contribution from the Department of Chemistry, Cornell University. This article is based upon part of the thesis presented t o the Faculty of the Graduate School of Cornell Yniversity by Katharina 11.Tressler in partial fulfillment of the requirements for the degree of Doctor of Philosophy. Dennis. TresslersndHance, J. Am. Chem. Sac., 4 4 , 2 0 3 3 ( 1 9 2 3 ) . 4 Dennis, Tressler and Nance: lor. cit.
K.4THARINA M. T R E S S L E R AND L. AI. DESSIS
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Expt. S o . 1 Charge
g. GeOz (containing z.q,C/c of H,O) I . j j g. sugar carbon I O g. salt 7.2
Tield 4.32 g. metal
GeOnrecovered from salt Total
Expt. S o . 2 Charge
Same as S o . I
l-ield 4 . 3 4 2 g. metal
Ge02recovered from salt 3303 g.
GeOzfrom tube "732 g.
Total
Expt. S o . 3 Charge
g. GeOz 10.6 g . tartaric acid 7.2
Yield 4 300 g. metal
GeO? recovered from salt 6190
IO
g. salt
GeO? from tube 0066
Total To obtain more even heating and more definite control of temperature, a graphite crucible 1 4 cm. high and 5 cm. inner diameter was used, the crucible being covered with a flanged lid that had an opening in the middle over which a tall, hard-glass tube was placed. Air was drawn up through this tube as in the earlier experiments. The crucible was imbedded in sand and was heated in an induction furnace. Since it was impossible to make measurements of the temperature of the inside of the crucible during the run, an empty crucible was heated in the furnace and the inner temperatures were read with an opcal pyrometer. With a current of 4.5 kilowatts per hour, the temperature at, the bott,om of the crucible remained constant at about I 130°, while half way up the side of the crucible the temperature was about IOOOO. I n the first run 4.5 kilowatts per hour were used. Expt. S o . 4 Charge Conditions 21.69 g. GeOn (3% HzO) 40 minutes heating 2 5 g. S a c 1 4 1 kilowatts per hr. Yield Metal (Consisted of small granules scattered through the flux.) I 2.7605 g. 85.072 Wt. GeOa recovered from tube '3238 1.5% Wt. GeO, recovered from S a C l 2.450 11.637~ Total Germanium accounted for 98.13%
1431
GERMANIUM. XX
The metal in this experiment was not completely fused together. The current wm therefore stepped up to 6 kilowatts per hour and the heating was somewhat longer.
Expt. No. 5 Charge Same as Expt. 4
Conditions minutes heating 6 kilowatts per hour
jj
Yield Wt. of metal ingot obtained 13.50 g. Wt. GeOzrecoveredfrom tube .3967 g. Wt. GeOzrecovered from XaC1 1.2490 g.
90
7%
83%
5.80%
Total Germanium accounted for
Expt. SO. 6 Charge Same as Expt. 4
0
1
97.6376
Conditions kilowatts per hour for 30 minutes. 6 kilowatts per hour for for z 5 minutes longer.
4 j-5
j
Yield Wt. of metal obtained In experiment S o . 6 part of the charge did not fuse and drop toward the bottom of the crucible.
Expt. S o . 7 Charge Same as Expt. 4
Conditions kilowatts per hour for 30 minutes. 6 kilowatts per hour for 2 j minutes longer 4. j - j . 5
Yield Wt. Metal I3 4 j g . Wt. GeOZrecovered from tube 4970 g. \Yt. GeOPrecovered form YaC1 I 16jjg. Total Germanium accounted for
89 i o 5 2
3%
-70 97 85%
An arc spectrogram of the metal, kindly made for us by Professor Papish, showed that the germanium was free from other substances in amounts greater than o.oI'?~, apart from any germanium oxide that might be present. Solution of a sample of the product in hydrogen peroxide indicated that the metal contained approximately one per cent. of germanium dioxide. The results show that about two per cent. of the germanium is volatilized, and that about six per cent. is recoverable for the flux. The germanium unaccounted for, two to three per cent., probably escaped extraction after the
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KATHARINA hl. TRESSLER AND L . M. DENXIS
fusion, for, with the small charges which were used, it was present in only small amount in a large quantity of the flux. It is also possible that some germanous oxide volatilizes through the walls of the graphite crucible. This difficulty could be avoided by fitting a porcelain crucible inside the graphite crucible. The chief advantage of this method of preparing metallic germanium from germanium dioxide lies in the fact that any desired amount of dioxide, limited only by the size of the crucible, may be reduced in a short time and the metal obtained in massive form.
summary A new method for the preparation of fused metallic germanium directly from germanium dioxide by reduction with carbon under a flux of sodium chloride is described. The yield of metal by this method is about 9 0 7 ~and about 7 7 0 of germanium charged is recoverable. n’ith larger charges and slight modification in the procedure, the loss of germanium will probably be negligible. Ithaca, New York.
