THE DI-SACCHARIDES. 195 



probably to be regarded as ethers, i.e., the two hexose groups 

 are probably connected together through an atom of oxygen. 

 Cane sugar has no reducing power on copper salts and forms 

 no osazone ; it, therefore, probably contains no aldehyde nor 

 ketone groups. Milk sugar and maltose yield these reactions 

 and probably contain the aldehyde group CHO. 



The decomposition of the di-saccharides into hexoses or 

 monoses by the addition of a molecule of water (hydrolysis) 

 can be brought about by the action of unorganised ferments or 

 enzymes, e.g., diastase, ptyalin, invertin, &c., or by boiling 

 with water and a little acid. 



Cane Sugar, Saccharose, Saccharobiose, C^H^On, the 



most important sugar, occurs in many plants ; in large quanti- 

 ties in the sugar-cane, in the maple, in beet-root, and in 

 sorghum cane. The juice of the sugar-cane (Saccharum offici- 

 narum) contains from 16 to 18% of its weight of sugar. Beets 

 contain from 7 to 16 %. Cane sugar is also present in the 

 juice of unripe maize, in many palms, in many roots, e.g., 

 turnips, mangolds, &c., in the sap of the lime, birch, &c., in 

 the nectar of flowers, and, mixed with glucose and fructose, 

 in many fruits. 



Commercial sugar is chiefly prepared from the sugar-cane, 

 the beet, and the sugar-maple. The properties of sugar are 

 well known and need not be described here. It melts at 160, 

 and at 190 or 200 changes to a brown uncrystallizable sub- 

 stance known as caramel, used in colouring. It does not 

 reduce copper salts. Boiled with dilute acids or by the action 

 of certain ferments, it is converted into a mixture of glucose 

 and levulose (inversion). It combines with lime and baryta to 

 form sparingly soluble saccharates, e.g., C^H^On.CaO.SELjO 

 and C 12 H 22 O u .3CaO. These substances are decomposed by' 

 carbon dioxide, yielding a metallic carbonate (insoluble) and 

 sugar. Cane sugar in plants is mainly contained in the stalks, 

 while the hexoses occur chiefly in the fruits. 



Milk Sugar, C^H^On + HA will be described in Chap. XV. 



Maltose, Malt Sugar, Maltobiose, C 12 H 2 . 2 O n + H 2 O, is formed 



o 2 



