86 



CHEMISTRY. 



which is generated and escapes is carbonic acid. The chemical 

 change which is produced is the conversion of one atom of anhy- 

 drous grape sugar into two atoms of alcohol, and four atoms of car- 

 bonic acid. 



Two atoms of alcohol - - - C^H^O* 



With four atoms of carbonic acid, - - C* O^ 



Form one atom of sugar, - - . C^^H'^O^ 



In the process of fermentation, the yeast, or ferment, itself under- 

 goes no change whatever ; its action being merely that of catalysis. 



The various kinds of fermented liquors, such as wine, cider, beer, 

 &c., are made from the juices of different fruits, or from infusions 

 of gram. These all contain sugar, and a fermenting principle, and 

 hence will undergo the vinous fermentation, provided they be exposed 

 to a proper temperature. The amount of alcohol contained in the 

 fermented liquors varies from 3 to 20 per cent. By distilling any 

 of the fermented liquors, the different spirituous liquors, or ardent 

 spirits, are procured ; these contain about 50 per cent, of alcohol ; 

 and by a second distillation, they yield the commercial alcohol, or 

 rectified spirit, which has a density of -835, and which yet contains 

 about 14 per cent, of water. 



Pure or absolute alcohol cannot be obtained by any number of 

 distillations, unless quicklime, chloride of calcium, or sulphuric acid 

 be employed at the same time, to combine with the water. 



Pure alcohol is colourless and limpid ; has a sp. gr. of -793 ; is 

 inflammable, burning with a pale bluish flame, and yielding water 

 and carbonic acid ; boiling point, 173° ; unites with water in all pro- 

 portions ; also with ether ; has powerful solvent powers ; it has never 

 been frozen by the most intense cold. 



The process of making bread is an instance of the vinous fermen- 

 tation : the yeast added to the dough, converting a small portion of 

 its sugar into carbonic acid and alcohol. The gas thus liberated, 

 forces the tough and adhesive mass into bubbles ; these still further 

 expand by the heat of the oven, which at the same time dissipates 

 the alcohol. 



Chlm-ide of Ethyl— Hydrochloric Et?ier.— This is prepared by the 

 action of hydrochloric acid on alcohol, the products being collected 

 in a cold receiver ; or else alcohol may be added to the materials for 

 generating hydrochloric acid, viz., common salt and sulphuric acid. 

 The rationale is precisely similar to that of hydrochloric acid on a 

 metallic oxide. 



Prop. — A colourless limpid liquid, very volatile, of a penetrating 

 aromatic odour; sp. gr. •874; boils at 52°; soluble in 10 parts 

 of water. 



