144 STARCH. 



liquid thus obtained to stand for some time. The 

 cells and membranes which inclose the starch are 

 thus broken and destroyed, and as the starch is inso- 

 luble in cold water, it is then easily washed out, and 

 separated from the husk and other insoluble parts of 

 the grain ; the w^ater is then allowed to settle, the 

 starch falls to the bottom, and is collected and dried. 



329. This softening and destruction of the mem- 

 branes of the seed is greatly assisted by the presence 

 of a small quantity of certain acids in the water, 

 which dissolves the gluten ; a small quantity of lactic 

 acid is always produced when grain is thus steeped 

 in water, and this is essential to the manufacture of 

 starch. A similar effect may be produced by a weak 

 alkaline solution, and accordingly a dilute solution 

 of caustic soda is employed by starch-makers to 

 soften particular sorts of grain, such as rice, Indian 

 corn, &c. (377). 



830. When grated potatoes are placed on a sieve, 

 under a stream of water, a very large quantity of 

 starch may be washed out. The starch will soon 

 settle to the bottom of the water, the soluble matters 

 of the potato, will be dissolved, and at last, there will 

 remain on the sieve little else beside the lignin or 

 fibre which the potatoes contained, together with a 

 quantity of starch which cannot be separated from 

 the fibre by mere washing. 



331. Potato-flour, arrowroot, tapioca, and sago, 

 are all varieties of starch ; similar substances are 

 likewise obtained from Iceland moss, the seed of the 



