tS2 CHEMISTRY POR AGRICULTURAL STUDENTS 



These alcohols are all monohydric, but, as is the case with inorganic 

 hydroxides, polyhydric alcohols can exist. For instance, it was found 

 that cellulose contained six replaceable hydroxyl groups. Glycerine is a 

 trihydric alcohol derived from propane, having the formula C3H5(OH)3, 

 glyceryl trihydroxide, and it forms, when treated with nitric and 

 sulphuric acids, a glyceryl trinitrate, or "nitroglycerine," which, when 

 mixed with infusorial earth, constitutes the explosive dynamite. 



Brewing. — Malt is prepared by steeping barley in water, then exposing 

 the softened grain to the air till germination has taken place, in order that 

 the soluble ferment diastase may be produced, and finally drying in kilns. 

 The radicles or *' combes" having been separated from the corn by treading 

 and sifting, the malt is crushed and mashed with water at about 7o\C. 

 During this process the starch is gelatinised and converted into dextrin and 

 maltose by the diastase previously formed, and the soluble carbohydrates 

 thus produced are extracted. The liquor or wort, when separated from 

 the spent " brewer's grains," is next boiled with hops ; then, after cooling, 

 fermented with yeast, alcohol and carbonic acid gas being formed. After 

 sufficient fermentation has taken place, and two or three per cent, of alcohol 

 has been produced, the yeast is skimmed off the surface, and the beer stored 

 in casks. Wines are prepared by directly fermenting grape juice. Spirits 

 are the products of distillation of wine and other fermented liquors. 



