Cane sugar C_{12}H_{22}O_{11}. Milk sugar C_{12}H_{22}O_{11}. Dextrose C_{6}H_{12}O_{6}. Levulose C_{6}H_{12}O_{6}. Cellulose C_{6}H_{10}O_{5}. Starch C_{6}H_{10}0_{5}. ~Cane sugar~ (C_{12}H_{22}O_{11}). This is the well-known substance commonly called sugar. It occurs in many plants especially in the sugar cane and sugar beet. It was formerly obtained almost entirely from the sugar cane, but at present the greatest amount of it comes from the sugar beet. The juice from the cane or beet contains the sugar in solution along with many impurities. These impurities are removed, and the resulting solution is then evaporated until the sugar crystallizes out. The evaporation is conducted in closed vessels from which the air is partially exhausted. In this way the boiling point of the solution is lowered and the charring of the sugar is prevented. It is impossible to remove all the sugar from the solution. In preparing sugar from sugar cane the liquors left after separating as much of it as possible from the juice of the cane constitute ordinary molasses. Maple sugar is made by the evaporation of the sap obtained from a species of the maple tree. Its sweetness is due to the presence of cane sugar, other products present in the maple sap imparting the distinctive flavor. When a solution of cane sugar is heated with hydrochloric or other dilute mineral acid, two compounds, dextrose and levulose, are formed in accordance with the following equation: C_{12}H_{22}O_{11} + H_{2}O = C_{6}H_{12}O_{6} + C_{6}H_{12}O_{6}. This same change is brought about by the action of an enzyme present in the yeast plant. When yeast is added to a solution of cane sugar fermentation is set up. The cane sugar, however, does not ferment directly: the enzyme in the yeast first transforms the sugar into dextrose and levulose, and these sugars then undergo alcoholic fermentation. When heated to 160 deg. cane sugar melts; if the temperature is increased to about 215 deg., a partial decomposition takes place and a brown substance known as caramel forms. This is used largely as a coloring matter. ~Milk sugar~ (C_{12}H_{22}O_{11}). This sugar is present in the milk of all mammals. The average composition of cow's milk is as follows: Water 87.17% Casein (nitrogenous matter) 3.56 Butter fat 3.64 Milk sugar 4.88 Mineral matter 0.75 When _rennin_, an enzyme obtained from the stomach of calves, is added to milk, the casein separates and is used in the manufacture of cheese. The remaining liquid contains the milk sugar which separates on evaporation; it resembles cane sugar in appearance but is not so sweet or soluble. The souring of milk is due to the fact that the milk sugar present undergoes _lactic fermentation_ in accordance with the equation C_{12}H_{22}O_{11} + H_{2}O = 4C_{3}H_{6}O_{3}.