ANHYDROUS ALCOHOL. 47 



little water which requires treatment with some chemical reagent 

 to ensure its complete removal. In order to obtain nearly an- 

 hydrous or " absolute " alcohol (alcohol free from admixture with 

 water) from wine or beer, the tolerably concentrated liquor obtained 

 by two or three successive distillations as in the last experiment, 

 collecting the first third or so each time, is placed in a bottle with 

 a quantity of solid carbonate of potassium (purified pearl ashes). 

 This substance has a strong attraction for water, and dissolves 

 freely therein, forming a solution with which alcohol will not mix ; 

 so that after a while the contents of the bottle separate into two 

 layers of liquid floating one on the other like oil on water ; the 

 top layer is alcohol almost wholly free from water, which can be 

 poured off into another bottle and preserved, whilst the heavier 

 liquid is a solution of the carbonate of potassium in the water 

 withdrawn from the spirit. 



Another way in which absolute alcohol can be prepared from 

 spirit already of considerable strength is by putting some lumps of 

 freshly burnt quicklime in a glass flask, and then pouring the spirit 

 on to them and corking up the flask for twenty-four hours ; a cork 

 and piece of bent tube are then affixed to the flask and the spirit 

 distilled off and condensed by means of a " Liebig's condenser " 

 (fig. 24), the heat being applied not by directly heating the flask 

 with a lamp but by placing it in a vessel of water which is gradu- 

 ally heated to boiling ; this contrivance is termed a water-both^ and 

 is identical with the arrangement used in an ordinary gluepot and 

 certain cooking utensils to avoid overheating (vide Expt. 89). 



If the spirit used in this experiment is not pretty strong to 

 commence with, the lime is apt to get very hot and may burst the 

 flask ; the quicklime chemically combines with the water present, 

 becoming "slaked" in so doing (Expt. 240), whilst the alcohol 

 remains unchanged ; so that on applying heat the alcohol rises in 

 vapour whilst the water remains behind combined with the 

 lime. 



Expt. 40. To Strengthen Weak Spirit by means of a Bladder. 

 Animal membranes, such as bladders, possess a remarkable 

 property, viz., that whereas they are readily porous towards water 

 they will not let alcohol pass through them at all easily. In con- 

 sequence, if a sheep's bladder be nearly filled with a mixture of 

 spirit with so much water that the mixture will not burn in a 

 spoon (about twice as much water as spirit will generally suffice), 

 and tightly tied up and hung up for a few days in a warm room, 

 it will be found that the contents of the .bladder have considerably 

 diminished in bulk by the passage of the water through the 

 bladder and its evaporation, but the strength of the liquor is so 



