DEXTROSE, grape-sugar, starch-sugar or dextroglucose, belongs to the class of Mono saccharides, in the section hexoses. Its formula may be expressed either as CoH,20e or C.11,0 (OH)g. Dextrose occurs along with levulose in very many plants, and notably in grapes and most other fruits; also in honey, and enters into the composition of many animal tissues and par ticularly in the blood, and also in the urine of diabetic patients. It can be produced by the action of dilute sulphuric acid on cane-sugar, starch, cellulose, etc. It can be best obtained by boiling for several hours 50 parts of starch with dilute sulphuric acid (100 parts of water to 5 parts of HiSO4). The solution is then neu tralized with chalk, filtered, boiled with ani mal charcoal to remove traces of color, and then evaporated carefully to dryness, forming an amorphous mass which contains about 60 per cent of dextrose, the remainder being chiefly dextrin. This mass is washed with cold, ethyl alcohol of specific gravity 0.830, and the residue dissolved in more alcohol. Upon cooling the pure dextrose crystallizes out. It may also be crystallized from a concentrated aqueous so lution at 90° to 95° F., and it then contains one molecule of water of crystallization, and forms microscopic rhombic crystals, which soften at 60°, melt at 86° and lose their water of crystal lization at 110°. Heated to 170° it is converted
into glucosan or dextrosan (CHu.O.), which may again be converted into dextrose by diges tion with water or dilute acids. Dextrose tastes much less sweet than ordinary cane-sugar. By the action of sodium am4gam dextrose is con verted into marmite, C.HHOs. A solution of dextrose becomes brown when boiled with caus tic alkalis.
Dextrose on oxidation yields in the first in stance gluconic acid, GIL(OH)..CO.H. Fur ther oxidation results in the formation of sac charic acid, C411,60..
In alkaline solution dextrose reduces com pletely the oxides of gold, platinum, silver and mercury, the metals being produced. With bis muth, lead, copper, iron, manganese, etc., par tial reduction takes place, only the lower oxides being formed. With sodium chloride, iodide and bromide, dextrose forms well-defined crys talline compounds which, however, decompose in aqueous solutions.
Nearly all true yeasts and a great many other organisms, and also zymase, ferment dextrose. In the presence of growing bacteria dextrose yields a variety of products, as lactic acid, bu tyric acid, cellulose, etc., depending on the species of bacteria present.