CARBOHYDRATES. 313 



and in 175 parts of alcohol ; when heated to 160 it fuses, and 

 the liquid, on cooling, forms an amorphous, transparent mass, 

 known as barley-sugar 5 at a higher temperature cane-sugar is 

 decomposed, water is evolved, and a brown, almost tasteless 

 substance is formed, which is known as caramel or burnt sugar. 

 Oxidizing agents act energetically upon cane-sugar, which is a 

 strong reducing agent. A mixture of cane-sugar and potassium 

 chlorate will deflagrate when moistened with sulphuric acid ; 

 potassium permanganate is readily deoxidized in acid solution ; 

 cane-sugar, however, does not affect an alkaline copper-solution. 



Melitose, C 12 H 22 U , is the chief constituent of Australian 

 manna. 



Maltose, C 12 H 22 O n , is a sugar resembling cane-sugar in some, 

 glucose in other properties ; it is formed along with dextrine 

 during the conversion of starch into sugar. 



Milk-sugar, Saccharum lactis, C 12 H 22 O n + H 2 = 360 (Lactose). 

 Found almost exclusively in the milk of the mammalia. Ob- 

 tained by freeing milk of casein and fat and evaporating the 

 remaining liquid (whey) to a small bulk, when the rnilk-sugar 

 crystallizes on cooling. 



It forms white, hard, crystalline masses; it is soluble in 7 

 parts of water (at 15) and in one part of boiling water, insolu- 

 ble in alcohol and ether ; it is much harder than cane-sugar, and 

 but faintly sweet ; it is not easily brought into alcoholic fer- 

 mentation by the action of yeast, but easily undergoes " lactic 

 fermentation," when cheese is added. During this process 

 milk-sugar is converted into lactic acid. 



Milk-sugar resembles grape-sugar in its action on alkaline 

 solution of copper, from which it precipitates cuprous oxide. 



Starch, Amylum, C 6 H 10 5 = 162. Starch is very widely dis- 

 tributed in the vegetable kingdom, and found chiefly in the 

 seed of cereals and leguminosse, but also in the roots, stems, 

 and seeds of nearly all plants. 



It is prepared from wheat, potatoes, rice, beans, sago, arrow- 

 root, etc., by a mechanical operation. The vegetable matter 

 containing the starch is comminuted by rasping or grinding in 

 order to open the cells in which it is deposited, and then steeped 

 in water ; the softened mass is then rubbed on a sieve under a 



