STARCH. 143 



are called, and subsequently dyed by being immersed 

 in the colored solution (542). 



325. When wood is distilled, or roasted in close 

 vessels, various substances are formed; amongst these 

 are vinegar or pyroligneous acid (488), and wood or 

 pyroxylic spirit. The latter is a volatile, pungent- 

 smelling liquid, which burns easily, with a pale flame 

 like spirit of wine. It is much used by hatters, var- 

 nish-makers, and others, as a solvent for resins. 



326. Starch is almost always found in considerable 

 quantity in all parts of plants. When pure it is a 

 white powder, insoluble in cold water, but readily 

 dissolving in that fluid when boiling hot. There are 

 many difl'erent varieties of starch, distinguished from 

 one another by some peculiar property, and which 

 have received various names, according to the plant 

 from which they are obtained. Common wheat 

 starch, which exists in large quantities in the seed of 

 wheat, is a good example of the general character of 

 this substance. 



327. When starch is dissolved in hot water, it 

 forms a thick, viscid, semi-transparent liquid, which if 

 evaporated leaves a yellowish, transparent, horn-like 

 substance, which readily swells and softens in cold 

 water. Hot water, though it greatly changes the 

 appearance and properties of starch, does not in any 

 way alter its chemical composition. 



328. Starch is obtained from wheat by steeping it 

 in water, and subsequently squeezing and washing 

 the softened grain, and then allowing the milky 



