Section III, 1919 [259] Trans. R.S.C. 



A Hydrate of an Oxonium Compound 



By O. M A ASS and J. Russell 



Presented by Professor R. F. Ruttan, F. R.S.C. 

 (Read May Meeting, 1919.) 



In the following paper it will be shown that there exists at low 

 temperatures a termolecular compound between ether, hydrobromic 

 acid and water, which may be termed a hydrate of the oxonium com- 

 pound ether-hydrobromide^ 



It may be well to review in a few words the facts which suggested 

 the investigation. It has often been noticed in the examination of 

 binary systems that where combination between the components 

 occurs, the substances are easily soluble in one another. For example, 

 anhydrous hydrobromic acid dissolves quite easily in ethyl benzene 

 and molecular compounds have been shown to exist in this system; 

 while in benzene, with which the acid forms no compound, it is almost 

 insoluble at atmospheric pressure. Also, it is well known, that, in 

 general, water is insoluble in pure liquids at low temperatures. If 

 ether, which is not quite anhydrous, is cooled to a low temperature 

 ( — 78°C.', the temperature of solid carbon dioxide), all the water is 

 precipitated as small crystals, even traces appearing in the form of a 

 cloud-. Water is also found to be absolutely insoluble in liquid hydro- 

 bromic acid at the same temperature. But if water be added to a mix- 

 ture of the ether and the acid it dissolves readily to form a clear 

 solution. The behaviour of the hydrocarbons seemed to indicate that 

 ease of solubility was accompanied by compound formation and it 

 was therefore deemed possible that in this latter case some compound 

 was formed between the three substances. This possibility lends 

 itself to investigation by means of a freezing point curve in which 

 the oxonium compound is treated as one component with water as 

 the second. 



The hydrobromic acid used was prepared by dropping bromine on 

 red phosphorus immersed in water, passing the gas thus evolved 

 through wash-bottles containing phosphorus to remove traces of 

 bromine, and through phosphorus pentoxide tubes to dry it. It was 

 finally condensed by means of solid carbon dioxide ether mixture. 



iJ.A.C.S. 34, 1273 (1912). 

 2J.A.C.S. 34, 1275 (1912). 



