ALCOHOL. 



quantity of water. The density of the distilled liquid dimi- 

 nishes with the proportion of alcohol, and tables have been 

 constructed by which from its density the per-centage of alcohol 

 in the liquid may be ascertained. Ordinary spirits have a 

 specific gravity from 0.910 to 0.915, which corresponds with 

 from 50 to 52 per cent, of alcohol. The same distilled afford a 

 spirit of density from 0.890 to 0.880, at 6*0, known as spirits 

 of wine, containing from 62 to 67 per cent of alcohol ; which 

 again may be brought, by a second distillation, to from 0.843 

 to 0.835, known as rectified spirits, and these contain from 

 82 to 85 per cent, of alcohol.* To obtain alcohol free from 

 water, or absolute alcohol, rectified spirits may be poured into 

 a retort over their weight of anhydrous lime, in fine powder, 

 either fresh quick-lime finely pulverised, or better lime that has 

 been slaked and afterwards heated recently to redness, allowed 

 to digest together for twenty-four hours, and the spirit after- 

 wards slowly distilled by the heat of a water-bath. It then has 

 a specific gravity of 0.7947 at 59 (15 cent.), and from 0.792 to 

 0.791 at 68 (20 cent.). The proof spirits of the excise, upon 

 which the duty per gallon is levied in this country, is of density 

 0.918633; and by the expression that a spirit is any number, 

 say ten, over proof , is meant that 100 gallons of the spirit would 

 stand the addition of ten gallons of water to reduce it to proof 

 strength, or it would form 1 10 gallons of proof spirit ; while ten 

 underproof, means that ten gallons of water must be taken from 

 100 gallons of the spirit to raise it to proof, or that 100 gallons 

 of it contain only 90 gallons of proof spirit. The proof 

 spirit of the pharmacopeia (spiritus tenuior) is directed to be of 

 sp. gr. 0.930. When obtained from grain, alcohol always con- 

 tains a small quantity of a particular oil, from which it is most 

 easily purified on the small scale by distilling it from caustic 

 potash, or filtering it, when in a large quantity, through a bed 

 of recently prepared wood charcoal, roughly pounded. 



Alcohol has never been frozen. By evaporating the com- 

 pound of solid carbonic acid and ether, in the vacuum of an air- 

 pump, Dr. Mitchell has produced the greatest depression of 

 temperature hitherto attained. Alcohol of specific gravity 0.798, 

 was observed by him to become oily and adhesive at 130; 



* Table of the Density of Alcohol, by M. Lowitz, see Appendix. 



