ETHYL ALCOHOL 391 



mixture is therefore cooled artificially, so that the temperature 

 is maintained steady at about 27 -5 -30. 



During this time the maltose is converted first into dextrose 

 and then into alcohol and carbon dioxide according to the 

 equations : 



CHH^OU + H 2 = 2C 6 H 13 6 



C 6 H U O S = 2 C 2 H 5 OH + 2CO 2 



In order to convert the dextrin, which would otherwise be 

 lost, into a fermentable substance, the temperature towards 

 the end is maintained at about 26-29 m order to give the 

 malt a further opportunity of hydro lysing the dextrin to 

 glucose, and so rendering it capable of being fermented by 

 yeast When the fermentation is completed after about three 

 days, the mixture contains about 13 per cent of alcohol by 

 volume; by distilling the mixture through a fractionating 

 column, so much of the water is removed that the distillate 

 contains about 80 to 95 per cent of alcohol.* 



No amount of fractional distillation without dehydrating 

 agents will produce alcohol contairfing less than 4-43 per cent 

 by weight of water, since such alcohol gives a constant boiling 

 mixture. 



Alcohol containing 0*5 per cent or less of water is, in 

 commerce, known as absolute alcohol, although in a scientific 

 laboratory the term is only correctly applied to alcohol which 

 is quite free from moisture ; such alcohol can only be obtained 

 by careful fractionation from freshly burnt quicklime.f If 

 the alcohol is dehydrated over quicklime to which a little 

 barium oxide has been added, complete dehydration is marked 

 by the formation of a yellow colour due to the production of 

 barium ethylate, which can only be formed in the absence of 

 any trace of moisture. 



A delicate test for the detection of traces of moisture in 

 alcohol consists in adding a few drops of the sample to a 

 solution of liquid paraffin in anhydrous chloroform ; if there 

 is any moisture present, a turbidity will be at once produced. 



* The residue remaining after distillation contains, in addition to the solid 

 un fermentable materials, a certain amount of other soluble products of fermenta- 

 tion, such as glycerol and succinic acid ; it is used as a cattle food. 



t Occasionally the last traces of moisture are removed by treating the alcohol 

 with sodium wire. 



