180 Mr GRAHAM'S Account of the Formation of Alcoates. 



able property which it possesses. It is capable of absorbing the 

 vapour of absolute alcohol, in the same manner as it absorbs the 

 vapour of water. I was led to make this observation from a con- 

 sideration of the phenomena which attend the mixing of alcohol 

 and sulphuric acid. Nearly as much heat is evolved as if water 

 had been added to the acid, even although absolute alcohol be 

 employed. Alcohol is also retained by the acid when heated to 

 500 or 600, or at a temperature when the alcohol would be 

 decidedly in the state of vapour, which indicates the possibility 

 of the same relation between sulphuric acid and alcohol vapour, 

 that subsists between water and those gases which it detains in 

 the liquid state, such as ammoniacal gas, when they would na- 

 turally assume the elastic form. But besides merely detaining 

 such gases, water can condense and absorb them. Sulphuric 

 acid, besides merely detaining alcohol vapour, might therefore 

 condense and absorb it. 



As alcohol, like water, occasions cold by its evaporation, it 

 may be substituted for water in Mr LESLIE'S frigorific appara- 

 tus, sulphuric acid being retained as the absorbing liquid. In 

 circumstances precisely similar, it was found that a thermometer, 

 the bulb of which was covered with cotton, fell to 7 when moist- 

 ened with water, but when moistened with absolute alcohol its 

 temperature fell to 24. Continuance of the pumping during 

 the experiment, as is done in the case of ether, had a prejudicial 

 effect. But alcohol diluted with a third of water was found to 

 have as great a cooling power as absolute alcohol. The advan- 

 tage to be derived from the great volatility of alcohol appears to 

 be counterbalanced in part by the small latent heat of its vapour. 

 Probably a mixture of alcohol and water, in certain proportions, 

 would produce the greatest degree of cold attainable by this 

 process. Sulphuric acid loses its power to absorb alcohol vapour 

 by being diluted with water. When impregnated with alcohol 

 vapour, the acid becomes of a pink colour ; but no appreciable 



