ELEMENTARY PHYSIOLOGICAL CHEMISTRY 165 



Their structure can be demonstrated by hydrolysing them, i.e. by 

 causing them to take up a molecule of water, in consequence of which 

 they split up. 



The chief means of hydrolysing include boiling with a weak 

 acid, the action of the succus entericus and of certain organised 

 ferments. 



The members of this class are cane sugar, maltose, and lactose, and 

 of these cane sugar does not reduce metallic oxides in alkaline solution, 

 nor does it form an osazone, whereas lactose and maltose give both 

 these reactions. With yeast they are first hydrolysed, and the mono- 

 saccharides thus produced then undergo alcoholic fermentation. 



Cane Sugar (C 12 H 22 O n ) is the common sugar obtained from sugar 

 cane, beet root, etc. It is very soluble in water, and has a sweet taste. 



It does not reduce metallic oxides in alkaline solution. 



EXPERIMENT VII. Perform Trommer's test with some cane sugar 

 solution. Notice that, although no reduction occurs, the cane sugar 

 is capable of holding the cupric hydrate in solution, so that a clear 

 blue colour is produced as it was with dextrose. By hydrolysis, 

 reducing sugars are developed. 



EXPERIMENT VIII. Boil some cane sugar solution with a few drops 

 of 25% sulphuric acid. Now neutralise and apply Trommer's test and 

 notice that reduction occurs. The monosaccharides developed are 

 dextrose and laevulose. 



DEMONSTRATION III. A solution of cane sugar is dextro-rotatory, 

 but after hydrolysis it is laevo-rotatory, the laevo-rotatory power of the 

 laevulose being stronger than the dextro-rotatory power of the dextrose 

 formed. On this account the process of hydrolysis is sometimes called 

 Inversion, and the hydrolysing agent in the succus entericus is called 

 an inverting ferment. Yeast also contains an inverting ferment. 



Lactose (C 12 H 9 . 2 O n ) is the sugar found in milk, and it has been 

 detected in the urine of nursing mothers. 



It is not very soluble in water, and is quite insoluble in alcohol and 

 ether. It has only a slightly sweet taste. It does not readily ferment 

 with yeast, but it undergoes a special fermentation with another 

 organism which results in the production of lactic acid. 



/OH 

 C 19 H 22 U + H 2 = 4CH 3 - CH< 



X COOH 



Lactose. Lactic acid. 



It reduces metallic oxides in alkaline solution. It is dextro-rotatory. 



Maltose (C 12 H 22 O n ) is important physiologically because it is the 



sugar produced from starch by the action of ptyalin, the ferment of the 



