DEXTRIN (Cials•00), the commercial name for a group of substances obtained from starch, and very similar to it in composition; also called starch gum, British gum, etc. It resembles gum in being soluble in water, but is distinguished from that substance by composi tion; by being, like starch, converted into oxalic acid by nitric acid, and not into mucic acid; and especially by causing a ray of polarized light to deviate to the right, a property from which it derives its name. The simplest member of the group of dextrins is malto dextrin, and this is the only one which has been obtained in a state approximating 'purity. For commercial purposes, dextrin is prepared from starch by heating dry starch to a temperature of from 400* to 480° F., in an iron cylinder revolving over a free flame or in an oil bath — usually rape seed oil. When the starch is first moist ened with nitric or hydrochloric acid, the prod uct is whiter but less adhesive as it then con tains some sugar. After roasting to the right degree, as indicated by an iodine test, it is quickly cooled to check further conversion. The product is an indefinite mixture of several dextrins with unaltered starch. The transfor mation may be effected also by the action of dilute sulphuric acid at a temperature a little below that of boiling water. The result in this
action is a mixture which contains some dextrin but is mostly dextrose (q.v.). By acting upon starch with diastase (q.v.) dextrin is pro duced. To water at about 70° or 80° F., in a boiler, 8 or 10 parts of dried malt are added, and then 100 parts of starch after the heat is raised to 140° F. The mixture is kept stirred' and the temperature maintained somewhat above this for 20 minutes, and then, when the thick mass has become quite fluid, it is raised to the boiling-point rapidly, cooled, the clear liquor filtered and evaporated to a syrup. When cold it is an opaque gelatinous mass, which, on drying, becomes hard like gum. It is then crushed, ground and sifted through silk. Dextrin is used in large quantities for thicken ing calico-printers' colors, as an adhesive for postage stamps, labels and adhesive papers, as a sizing for textiles and for many other pur poses. The corn syrup or glucose of the con fectioner and the manufacturer of table syrups contains dextrin to the amount of 42 per cent. See GLUCOSE.