ALCOHOL 



45 



mercial alcohol, is made to rest upon the lime ; the whole is placed under the low 

 receiver of an air-pump, and the exhaustion continued till the alcohol evinces signs 

 of ebullition. Of the mingled vapours of alcohol and water which now fill the re- 

 ceiver, the quicklime is capable of uniting with the aqueous only, which is therefore 

 rapidly withdrawn, while the alcohol vapour is unaffected ; and as water cannot 

 remain in the alcohol as long as the superincumbent atmosphere is devoid of 

 moisture, more aqueous vapour rises, which is likewise abstracted by the lime, and 

 thus the process goes on till the whole of the water in the alcohol is removed. Several 

 days are always required for this purpose.' 



Properties of Alcohol (Absolute). 



In the state of purity, alcohol is a colourless liquid, highly inflammable, burning 

 with a pale blue flame, very volatile, and having a density of 0792 at 15-5 0. (60 

 F.) (Drinkwater). It boils at 78'4 C. (173 F.) It has never yet been solidified, 

 and the density of its vapour is 1-6133. 



Anhydrous alcohol is composed by weight of 52*18 carbon, 13-04 hydrogen, and 

 34-78 of oxygen. It has for its formula C 4 H 8 O 2 = C 4 H s O + HO, or hydrated oxide 

 of ethyle. It has a powerful affinity for water, removing the water from moist 

 substances with which it is brought in contact. In consequence of this property, 

 it attracts water from the air, and rapidly becomes weaker, unless kept in very well- 

 stopped vessels. In virtue of its attraction for water, alcohol is very valuable for tho 

 preservation of organic substances, and especially of anatomical preparations, in con- 

 sequence of its causing the coagulation of albuminous substances ; and for the same 

 reason it causes death when injected into the veins. 



When mixed with water a considerable amount of heat is evolved, and a remark- 

 able contraction of volume is observed, these effects being greatest with 54 per 

 cent, of alcohol and 46 of water, and thence decreasing with a greater proportion of 

 water. For alcohol which contains 90 per cent, of water, this condensation amounts 

 to 1-94 per cent, of the volume ; for 80 per cent, 2-87 ; for 70 per cent., 3-44 ; for 60 

 per cent., 373 ; for 40 per cent, 3-44 ; for 30 per cent, 272 ; for 20 per cent, 172 ; 

 for 10 per cent, 072. 



Alcohol is prepared absolute for certain purposes, but the mixtures of alcohol and 

 water commonly met with in commerce are of aa inferior strength. Those commonly 

 sold are ' Eectified Spirit ' and ' Proof Spirit' 



'Proof Spirit' is defined by Act of Parliament, 58 Geo. III. c. 28, to be ' such as 

 shall, at the temperature of fifty-one degrees of Fahrenheit's thermometer, weigh 

 exactly twelve-thirteenth parts of an equal measure of distilled water.' And by 

 very careful experiment, Mr. Drinkwater has determined that this proof spirit has 

 the following composition : 



Spirit which is weaker is called 'under proof;' and that stronger, 'above proof.' 

 The origin of these terms is as follows : Formerly a very rude mode of ascertaining 

 the strength of spirits was practised, called the proof ; the spirit was poured upon 

 gunpowder and inflamed. If, at the end of the combustion, the gunpowder took fire, 

 the spirit was said to be above or over proof. But if the spirit contained much water, 

 the powder was rendered so moist that it did not take fire : in which case the spirit 

 was said to be under or below proof. 



Rectified spirit contains from 54 to 64 per cent of absolute alcohol and its specific 

 gravity is fixed by the London and Edinburgh Colleges of Physicians at 0-838, whilst 

 the Dublin College fixes it at 0-840. 



In commerce the strength of mixtures of alcohol and water are stated at so many 

 degrees, according to Sykes's hydrometer, above or below proof. This instrument will bo 

 explained under the head of ALCOHOLOMETRY. 



As will have been understood by the preceding remarks, the specific gravity or 

 density of mixtures of alcohol and water rises with the diminution of the quantity of 



