CARBOHYDRATES 73 



the sap of the sugar maple. It is a valuable food substance, 

 and serves also as a condiment, by its sweetness making other 

 foods more palatable. Cane sugar is prepared by treating the 

 sap or juice containing it with milk of lime. This neutralizes 

 any acids present, which otherwise would hydrolyze the sugar 

 during evaporation. After being boiled to remove the protein, 

 the calcium is removed by running in carbon dioxide, and the 

 solution is decolorized either with animal charcoal or sulphur 

 dioxide. After being boiled and filtered the liquid is evaporated 

 in vacuo, and the cane sugar crystallizes out. The remaining 

 liquid is known as molasses, and still contains considerable quan- 

 tities of sugar which may be obtained by precipitation as cal- 

 cium or strontium saccharate. From this compound the cane 

 sugar may be set free with carbon dioxide. 



Cane sugar is readily soluble in water, less so in alcohol, and 

 insoluble in ether. The aqueous solution is very sweet, and 

 is strongly dextrorotatory, the specific rotation being + 66.5. 

 The specific rotation of saccharose is practically independent of 

 changes in concentration and temperature, so that the property 

 is often made use of for its estimation. On hydrolysis it yields 

 glucose and fructose. 



On being heated to about 160 cane sugar melts and if al- 

 lowed to cool, forms a glassy mass which is known as barley 

 sugar. At about 200 it turns brown, forming caramel. 



CH 2 OH 



CH 2 OH 

 CHOH 



| CH_ 



CH I " 



CHOH 



I 

 CHOH ! 



CHOH 



I 

 CHOH 



CH 2 OH 



Saccharose 



