_Dextrose_ (C_{6} H_{12} O_{6}), occurs ready-formed in grape juice, and in many sweet fruits, very frequently associated with levulose; it is also contained in honey, together with a small amount of cane sugar. As already mentioned, it constitutes an ingredient of the product obtained by the action of acids and ferments upon cane sugar. For commercial purposes, glucose is prepared by treating grains rich in starch, with dilute acids. In France and Germany, potatoes are used in its manufacture; in the United States, Indian corn or maize is almost exclusively employed. The processes used consist substantially in first separating the starch from the grain by soaking, grinding, and straining, then boiling it, under pressure, with water containing about 3 per cent. of sulphuric acid, neutralising the remaining acid with chalk, decolorising the solution by means of animal charcoal, and concentrating it in vacuum pans. In the United States thirty-two factories are engaged in the manufacture of glucose, which consume about 40,000 bushels of corn daily, their annual production having an estimated value of 10 millions of dollars. In commerce, the term grape sugar is applied to the solid product, the syrup or liquid form being known as glucose. The chief uses of starch sugar and glucose are in the manufacture of table syrups, and as a substitute for malt in the brewing of beer and ale. Their other most important applications are as a substitute for cane sugar in confectionery, and in the preparation of fruit jellies; as an adulterant of cane sugar, as an admixture to genuine honey, and as a source for the preparation of vinegar. Dextrose is soluble in 1-1/5 part of cold water, and is much more soluble in hot water. It has a dextro-rotary power of 56°. When separated from its aqueous solution, it forms white and opaque granular masses, but from an alcoholic solution, it is obtained in well-defined, microscopic needles, which fuse at 146°. Two parts of glucose have about the same sweetening effect as one part of cane sugar.[54] It does not become coloured when mixed with cold concentrated sulphuric acid, which distinguishes it from sucrose; on the other hand, its solution is coloured dark-brown if boiled with potassium hydroxide, another distinction from cane sugar. Dextrose is capable of directly undergoing vinous fermentation, and, like invert sugar, it possesses the property of reducing alkaline solutions of copper salts, especially upon the application of heat. The chief commercial varieties of American glucose are the following:-- 1. _Glucose_: Per cent. Glucose. “Crystal H,” containing 40 “Crystal B” 45 “Crystal A” 50 2. _Grape Sugar_: “Brewers’ grape” 70-75 “A” or “Solid grape” 75-80 “Grained” or “Granulated grape” 80-85