GRAPE-SUGAR SUGAR OF MILK. 317 



of the process are chiefly filtrations with the aid of animal 

 charcoal, and finally concentration to the crystallising point. 

 The crystals of beetroot- sugar are longer and flatter than 

 those of cane-sugar, but cannot otherwise be distinguished from 

 cane-sugar. 



Grape or Starch Sugar. Starch -sugar or grape -sugar is 

 prepared by heating starch in a very dilute solution of sul- 

 phuric acid, the acid being afterwards separated by means of 

 chalk. The sugar of starch is also called glucose. It is the 

 same kind of sugar which is formed abundantly in the human 

 body in the disease termed diabetes. It is less soluble in water 

 than cane-sugar, yet is more readily taken up by alcohol. It 

 has less than half the sweetening effect of cane-sugar. 



Sugar of Milk. Sugar of milk is an animal product. It 

 is obtained in largest proportion from the milk of herbivorous 

 animals, yet is contained in the milk of animals which are 

 purely carnivorous. It has a less sweetening effect than the 

 sugar of starch. It is less soluble than the cane-sugar or than 

 the sugar of starch. When pure the sugar of milk is not 

 susceptible of fermentation ; milk, however, is capable of fer- 

 mentation, and therefore of affording alcohol. 



Fructose, or Sugar of Fruits. It was once supposed that 

 there is a peculiar sugar in fruits different from the cane and 

 the grape sugar. It appears now that in many fruits the 

 cane-sugar is mingled with a proportion of inverted sugar 

 that is, the sugar into which a solution of cane-sugar first 

 passes when boiled for some time (p. 314). It is called inverted 

 sugar because while a solution of cane-sugar exerts a right- 

 handed rotation upon a ray of polarised light, this sugar has the 

 effect of causing a left-handed rotation on a polarised ray. 



Inverted Sugar. Inverted sugar is not crystallisable. It 

 can be procured only from cane-sugar by boiling, by the action 

 of acids, or by a peculiar albuminous ferment present in the 



