Il6 ORGANIC AGRICULTURAL CHEMISTRY 



which it occurs in exactly the same form as in the sugar cane. 

 It is also found in considerable amount in sorghum cane and in 

 the sap of maple trees, especially the hard or sugar maple {Acer 

 saccharum). Other rather abundant sources are vegetables 

 such as carrots, parsnips, artichokes, in such fruits as strawberries 

 and pineapples, in the sap of some other trees such as beech, and 

 in some nuts such as chestnuts. 



Properties. — Cane sugar is a crystalline solid, forming 

 monoclinic prisms. It is easily soluble in water and slightly 

 so in alcohol. It melts at i6o° C, and when melted and allowed 

 to cool it forms a transparent vitreous-like mass known as 

 barley sugar, which gradually becomes crystalline. When heated 

 to 210° C, it loses water and is converted into a brown amorphous 

 mass known as caramel which is used as a brown coloring agent, 

 and as a flavoring substance of a characteristic taste. Heated 

 still higher it decomposes, yielding finally a residue of carbon 

 and giving off water and a mixture of volatile products contain- 

 ing several hydrocarbons, aldehydes and acids. When sugar 

 is treated with concentrated sulphuric acid, it is decomposed with 

 the evolution of heat and a residue of carbon is left. (See 

 Experiment XX, i, c.) If this is washed to remove the acid, 

 pure carbon is obtained, and this is used as a method of making 

 pure carbon. Cane sugar is dextro-rotatory, but it does not 

 reduce Fehling^s solution. When pure cane sugar is treated 

 with Fehling's solution, reduction often occurs after some 

 minutes' boiling, because the sugar is first hydrolyzed into 

 glucose and fructose which then reduce the Fehling's solu- 

 tion. 



Cane sugar does not undergo alcoholic fermentation by the 

 action of the enzyme zymase as do glucose and fructose. Yeast 

 contains not only the alcoholic enzyme zymase but also enzymes 

 which hydrolyze cane sugar and the other disaccharoses. When, 

 therefore, cane sugar is subjected to yeast fermentation, alcohol 

 is produced, due to a double process. First the cane sugar is 

 hydrolyzed by the yeast enzyme sucrase or invertase and con- 

 verted into glucose and fructose. These monosaccharoses are 



