CHEMISTRY. oU 



powder, consisting of rounded, shining white particles. They 

 are tasteless and inodorous, and when kept dry undergo no 

 change in any length of time. Starch is insoluble in cold 

 water or alcohol, but dissolves readily in hot water, and forms 

 a jelly. Starch, like lignine, is composed of carbon, hydrogen 

 and oxygen. Starch is a delicate test for the presence of 

 iodine. 



Arroiv root, sago, tapioca, inulme and lichenine are varieties 

 of starch. It is frequently deposited among the woody fibres 

 and in the inner bark of trees, as the willow, beech and pine. 

 This is the reason, [says Prof. Johnston,] that the branch of a 

 willow takes root so readily, and also, that the bark of trees is 

 used in some countries as food. 



GUM. 



Gum arabic is a familiar example of this class of substances ; 

 the gum from peach and plumb trees is similar in constitution. 

 Pure gum is light colored, having a sweetish taste, destitute of 

 odor, insoluble in alcohol, soluble in water, with which it forms 

 an adhesive mucilage. Gum is composed of carbon, hydrogen 

 and oxygen : it exists in the seeds and other parts of many 

 plants. Arabine, carasine, bassorine, dextrine, and traga- 

 canthine are all varieties of gum: this, as well as starch, is 

 highly nutricious as food. 



SUGAR. 



Sugar exists in many plants, but is obtained principally 

 from sugar cane, sugar maple, and beet root. Pure sugar is 

 in large transparent crystals, having a pure sweet taste, desti- 

 tute of odor, soluble in water, highly nutricious. Its constit- 

 uent elements are carbon, hydrogen and oxygen. Grape 

 sugar, sugar of milk, and sugar of mushrooms, are all va- 

 rieties. 



