612 QRAMINEJE. 



metals ; glutin contains sulpliur and 18 per cent, of nitrogen. 



These principles are the most important ones of the vegetahle 



2)rotein compounds, [Stillc and 3IaiscJi.) 



Starch forms a white, inodorous, and tasteless powder, with 



a peculiar slippeiy feel between the fingers. Exposed to the 



atmosphere, it contains from 10 to 13 per cent, of moisture, 



which is given off at 100° C. (212° F.), and is reabsorbed on 



exposure. The spec. grav. of starch is about 1'5, but after 



complete drj'ing is increased to 1'56. It is insoluble in ether, 



alcoholj and cold water ; the last-mentioned liquid, however, 



when triturated with starch, so that some of the granviles are 



ruptured, evidently dissolves a little, since it acquires, after 



filtration, a blue color on the addition of iodine. Soluble starch 



is obtained, according to Maschke, by the prolonged heating of 



starch to 100" C. (212° F,). When heated to between 160" 



and 200° C. (320° and 392° F.), it is gradually converted into 



dcK-trin f see below). Starch becomes soluble in cold water in 



the presence of the chlorides of zinc and of calcium and of 



other deliquescent or freely soluble salts. Its solution in hot 



water gelatinizes on cooling, the jelly of wheat starch being 



milk-white— that of potato starch, particularly when made 



with much water, beinff more translucent. On heating starch 



with glycerin a solution is obtained, which, according to 

 Zulkowski (1875, 1880), contains soluble starch, obtainable 

 by diluting with water and precipitating the clear filtrate with 

 alcohol. Potato starch is easily converted into the soluble form, 

 but wheat starch requires a prolonged heating, and rice starch 

 is thus changed with still greater diSiculty, 



Preparation. — Wheat or other grain is soaked in warm 

 water, to which sometimes an alkali is added, until the outer 

 coating has become soft ; it is then ground under water, and 

 washed upon suitable sieves with pure water, with which the 

 starch passes through and is collected by subsidence in suitable 

 tanks, the alkaline water retaining the gluten ; or the latter is 

 removed by allowing it to undergo decomposition, when acetic, 

 butyric, or lactic and other acids are produced. The gluten 

 need not be destroyed, but mav be obtained as a by-product; 



