GUEST AUTHORS Kenneth E. Hayes and Nadine R. M. Haase Dalhousie University Halifax, Nova Scotia
Textbook Errors,
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The Thermal Stability
In the past ten years several textbooks1 have stated that hydrogen selenide may he readily hrokeu down thermally to the constituent elements, and lGO°C was even quoted as the temperature at which decomposition is measurable. This result, which does not appear to he documented in any of the texts, is at variance with the larger, older compilations usually described as authoritative. 2-3 Recently we had occasion to establish experimentally that, in contrast with the textbook statements, hydrogen selenide is in fact quite stable thermally. No decomposition was observed a t 280°C when we attempted to prepare a selenium film for another investigation by t,akingadvantage of the alleged instability of the hydrogeu selenide. A conventional high vacmm apparatus was used for an experimental test. Hydrogen selenide was preSuggestion of material suitahle for this column and guest eolumns suitable for publications directly are eagerly soliaited. They should be sent with as many details as pomible, and particularly with references to modern textbooks to Karol J. Mysels, Department of Chemistry, University of Sout,hern California, Los Angeles 7, California. I Since the purpose of this column is to prevent the spread and continuation of errors and not the evaluation of individual texts, the source of errors discumed will not be cited. The error must occur in at least two independent standard books to he presented. J. W., " 4 Comprehensive Treatise on Inorganic and MELLOR, Theorct,icnl Chemistry," 1,ongmans Green and Co., New York, 1930, Vul. S,p. 759. Pasc*~.,P., editor, "Trait,e de Chrmie Minerale," Masson et Cie, Paris, 1932, Tome 11, p. 347.
pared by the action of 10% sulfuric acid on iron selenide, the gas was roughly dried by pasage through a trap filled with anhydrous magnesium perchlorate and collected in a trap a t liquid nitrogen temperature. It was then purified by repeated distillation-sublimation in the conventional manner and sent to storage. The reactor was essentially a large Pyrex U-tube, to which was attached an all glass circulating pump, a thermocouple well and a manometer sensitive to 0.2 mm. The reactor was surrounded by an oil thermostat which permitted temperature control within the reactor t o 1 0 3 OC. The reactor was held a t 280°C 10.5" during all experiments. In a typical experiment, hydrogen selenide was introduced into the hot reactor up to a predetermined pressure, and its behavior observed over a period of time. The iuitial HzSe pressure was varied between approximately 5 and 120 mm of Hg. In no instance was there any evidence of decomposition over a three hour period. On the other hand, the introduction of approximately equal quantities of air dried over magnesium perchlorate into the reactor containing the hydrogen selenide caused rapid deposition of grey selenium on the cooler parts of the reactor. This occurred a t all pressures, hut faster a t the higher ones. Thus it may be concluded that contrary to the texts, pure hydrogen selenide is stable at least to 280°C and that the low temperature reaction, described by them, is probably due to the presence of impurities such as oxygen.
Volume 40, Number 3, March 1963
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