44 STARCH. 



oxygen. Now it is a curious point, that in this 

 woody fibre, hydrogen and oxygen are present in just 

 the proportions to form water. To this important 

 fact we shall refer again. 



In the stems, leaves, husks, bark, and in most cases 

 the roots, woody fibre is by far the largest constituent ; 

 but in the seeds and fruits, it is usually much smaller 

 in quantity. 



In a great number of seeds, starch is the leading 

 ingredient; so also in many roots that are used foi 

 food. a. Starch is in its usual appearance well known, 

 as a white, tasteless, or nearly tasteless substance. It 

 does rot dissolve even in warm water, but forms a 

 species of jelly with it. One peculiar property is that 

 of turning blue when iodine comes in contact with it. 

 The common tincture of iodine will answer for this 

 experiment: the smallest possible quantity will produce 

 an immediate effect. 



b. Starch may be easily obtained by making some 

 wheaten flour into dough, and then washing on a very 

 fine sieve or linen cloth placed above a convenient 

 vessel. As the dough is kneaded under successive 

 portions of water, the water becomes milky, and the 

 mass of dough constantly diminishes in bulk until at 

 last nothing but a sticky substance called gluten re- 

 mains ; to this we shall refer again. If the milky 

 liquid which has run through the cloth be allowed to 

 stand quiet for some hours, a deposit of fine white 

 grains will be formed on the bottom of the containing 

 vessel : this is the starch. 



c. It may also be easily extracted from the potato, 

 by grating fine and washing. The starch will settle 

 next the bottom; the skin, woody fibre, etc. will float 

 above, so that they ma) be poured off. In this way 

 potato starch is made. 



The composition of starch is carbon, hydrogen and 

 oxygen; the same, it will be remembered, as that of 



