THE ELEMENTS OF PLANT FOOD 35 



Third, the sirup is clarified by filters of bone black. 

 The sirup is now clear and colorless. Fourth, the 

 sirup is evaporated. To make the evaporation more 

 complete without changing any of the sugar to glucose, 

 this process is carried on in vacuum pans. This al- 

 lows boiling to take place at a lower temperature 

 than in the open air. Some sugar crystals are formed, 

 but the product has much sirup still remaining. Fifth, 

 the crystals are separated from the sirup by being 

 rapidly whirled in cone-shaped sieves, called centrifu- 

 gals. The mother liquor not crystallizing is molasses. 



Granulated sugar, then, is a pure crystallized car- 

 bohydrate commercially produced from sugar cane or 

 from sugar beets. If the crystals are dried in cubical 

 molds, it is called loaf sugar. 



If the juices after treatment with lime are heated 

 and a portion of the water evaporated to a certain 

 point, a sirup is obtained which when cooled turns 

 into sugar called brown sugar. 



Maple sugar is a sucrose with a distinctive flavor 

 derived from some of the other ingredients in the sap 

 of the maple tree. 



Sugar of Milk, Lactose, CioH^Oii + H 2 O. This 

 sugar is found in the milk of all milk-giving animals. 

 It is a by-product in the manufacture of cheese. The 

 casein is separated *from the milk by means of rennet. 

 The sugar of milk remains in the whey and may be 

 separated by evaporation and purified by recrystalliza- 

 tion. The crystallized product is used as a container 

 for medicines. It is not so sweet as cane sugar. Sugar 

 of milk constitutes about five per cent of cow's milk. 

 The souring of milk is caused by the fermentation of 

 sugar of milk forming lactic acid. 



