STARCH. Ci2 H10 010=12 atoms of carbon and 10 of water. This substanc,e occurs abundantly in vegetables, and is generally obtained by steeping the powdered grain or seed, or the raspings of the root, bulb, or stem in cold water, which becomes whit,e and turbid, mad, after being strained, deposits the starch in the form of a white granular substance which is then dried at a gentle heat.
Common starch is manufactured from flour. Arrowroot, tapioca, and sago are different forms of starch. Starch is frequently made from potatoes.
When starch is heated to a certain temperature, it becomes con verted into a gum called " Dextrine " (q. v.). It forms a blue com poimd with iodine, called iodide of starch, an aqueous solution of which is bleached by light : it combines also with sulphuric acid, forming sulphate of starch, and with lime and baryta ; also with tannin. Starch becomes converted into sugar by the action of an azotized principle, called "Diastase," and also by the action of dilute acid.s.
Starch is insoluble in cold water, alcohol, and ether. When boiling water is poured upon it, clots are formed which cannot afterwards be diffused through water. Solution of starch is best made by pounding the starch, and mixing it thoroughly with cold water ; then adding hot water, or boiling it, stirring it uniformly until a gelatinous mixture is obtained. A solution of starch is supposed to consist of the granules considerably distended and dif fused through the water. When, however, the indurated envelope of the starch granule bursts, the contents are distributed through the water, and form a transparent gelatinous liquid which, on cool ing, throws down an opalescent deposit. The substance held in solution in the clear liquid has been called " AMIDINE."