Mr. Graham's Account of the Formation ofAlcoates. 269 



ratus, sulphuric acid being retained as the absorbing liquid. 

 In circumstances precisely similar, it was found that a ther- 

 mometer, the bulb of which was covered with cotton, fell to 

 7° when moistened with water, but when moistened with ab- 

 solute alcohol its temperature fell to — 24*°. Continuance of 

 the pumping during the experiment, as is done in the case of 

 aether, 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 advantage 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 appretiable quantity of 

 gas is emitted at the temperature of the atmosphere, even in 

 the vacuum of an air-pump. 



From one experiment, water appears to have the power to 

 induce the evaporation of alcohol by absorbing its vapour, as 

 sulphuric acid does, but much more feebly. Two cups, one 

 containing alcohol and the other pure water, were inclosed 

 together in a tin-canister which was nearly air-tight, and set 

 aside in a quiet place for six weeks. The cups were not in 

 contact, but a little apart from each other. At the expiration 

 of that period it was found, on opening the canister, that the 

 cup which originally contained pure water, now contained a 

 mixture of water and alcohol, while the alcohol remaining in 

 the other cup was of diminished strength. Professor Leslie 

 informs me, that he performed a similar experiment a consi- 

 derable time ago, although no account of it was published. But 

 the absorption of alcohol-vapour by water is so feeble as not 

 to occasion a sensible reduction of temperature in the alcohol. 



Chloride of calcium is disqualified as an absorbent of aqueous 

 vapour in the purification of alcohol, for the same reason as 

 sulphuric acid. I find that chloride of calcium absorbs the 

 vapour of absolute alcohol, and runs into a liquid, or it deli- 

 quesces in alcohol- vapour. A small quantity of this substance 

 was suspended in a little capsule, at the height of two inches 

 above a quantity of absolute alcohol, in a close vessel. In the 

 course of twenty-four hours it was entirely resolved into a li- 

 quid, just as if it had been suspended over water. The liquid 

 proved to be a solution of chloride of calcium in absolute al- 

 cohol. The experiment was frequently repeated. As salts 

 which deliquesce from the absorption of aqueous vapour are 

 always capable of forming hydrates, I was led from the ob- 

 servation 



