268 Mr. Graham's Account of the Format ion of Alcoatcs. 



employed in the arts and in medicine. I believe, however, that, 

 by the excise laws as they at present exist, no rectifier of 

 spirits is permitted to concentrate alcohol beyond a certain 

 strength. Licensed apothecaries alone are allowed to prepare 

 and sell absolute alcohol *. 



Alcohol may be concentrated in a close vessel with quick- 

 lime, without exhausting; but the process goes on much more 

 slowly, at least at the temperature of the air. The experiment 

 was tried at a high temperature, by heating in a water-bath a 

 large bottle with a very wide mouth, containing a quantity of 

 alcohol at the bottom, and quicklime suspended over it in a 

 linen-bag. When the water-bath attained the temperature of 

 150°, the bottle was corked, and the bath prevented from be- 

 coming hotter. Much of the lime was very quickly converted 

 into hydrate, and the alcohol considerably concentrated. But 

 the process is troublesome, and much inferior to that in which 

 the air-pump is employed. 



In the place of quicklime, sulphuric acid cannot be sub- 

 stituted in the foregoing process as an absorbing liquid, from 

 a remarkable 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 ob- 

 servation from a consideration of the phaenomena which at- 

 tend 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 tem- 

 perature 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 be- 

 tween water and those gases which it detains in the liquid 

 state, such as ammoniacal gas, when they would naturally as- 

 sume the elastic form. But besides merely detaining such 

 gases, water can condense and absorb them. Sulphuric acid, 

 besides merely detaining alcohol-vapour, might therefore con- 

 dense and absorb it. 



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

 may be substituted for water in Mr. Leslie's frigorific appa- 



* Care should be taken that the temperature be nearly equable during 

 the experiment ; otherwise, when the atmosphere becomes cold, a conden- 

 sation of alcohol- vapour takes place upon the cooled bell-glass, which runs 

 down upon the plate of the pump. The experiment, therefore, should not be 

 performed in a room with a fire, or near a window, but in a dark closet or 

 press. From the manner in which I performed the experiment, this con- 

 densation had never been experienced by myself ; but Dr. Duncan junior 

 observed it, on repeating the process. 



ratus, 



