7 °2 
but particularly from wheat or from potatoes. To 
make starch from wheat, the grain is steeped in 
cold water till it becomes soft, and yields a milky 
juice by pressure ; it is then put into sacks of 
linen, and pressed in a vat filled with water : as 
long as any milky juice exudes the pressure is con- 
tinued : the fluid gradually becomes clear, and a 
white powder subsides, which is starch. 
Starch is soluble in boiling water, but not in cold 
water, nor in spirits of wine. It is a characteristic 
property of starch to be rendered blue by iodine. 
Starch is more readily combustible than gum ; 
when thrown upon red-hot iron, it burns with a 
kind of explosion, and scarcely any residuum re- 
mains. According to MM. Gay Lussac and The- 
nard, 100 parts of starch are composed of 
Carbon, with a small quantity of 
saline and earthy matter 
Oxygene - - - 49,68 
Hydrogene - 6,77 
or, 
Carbon - - - 4 3,55 
Oxygene and hydrogene in the') 
proportions necessary to form >56,45 
water - - - .J 
Supposing this estimation correct, starch may 
be conceived to be constituted by 15 proportions 
of carbon, 13 of oxygene, and 26 of hydrogene. 
Starch forms a principal part of a number of 
esculent vegetable substances. Sowans, cassava, 
salop, sago, all of them owe their nutritive powers 
principally to the starch they contain. 
Starch has been found in the following plants : 
