70 HOW CROPS GKOW. ■ 



of the flltrtite add one drop of strong sulpliuric acid, and boil a few- 

 minutes. Test wifli iodine, whicli will now prove that all the starch is 

 transformed. 



Not only heat, but likewise acids and fei-ment^ produce 

 dextrin from starch, and also from cellulose. In the 

 sprouting of seeds it is formed from starch, and hence is 

 an ingredient of malt liquors. It is often contained in 

 the animal body. Limpricht obtained nearly a pound of 

 dextrin from 200 lbs. of the flesh of a young horse. — An7i. 

 Ch. Ph., 133, p. 295. 



The chemical composition of dextrin is the same as that 

 of cellulose, starch, and inulin. 



Tlie Gums. — A number of bodies exist in the vegetable 

 kingdom, which, from the similarity of their properties, 

 have received the common designation of Gums. The 

 best known are Gum Arabic, or Arahin • the gum of the 

 Cherry and Plum, or Cerasin • Gum Tragacanth and Bas- 

 sora Gum, ot JBassorin ; and the Vegetable Mucilage of 

 various roots, viz., of mallow and comfrey; and of certain 

 seeds, as those of flax and quince. 



Ara1)in. — Gum Arabic or Arabin exudes from the 

 stems of various species of acacia that grow in the tropi- 

 cal countries of the East, especially in Arabia and Egypt. 

 It occurs in tear-like, transparent, and, in its purest form, 

 colorless masses. These dissolve easily in their own weight 

 of water, forming a viscid liquid, or mucilage, which is em- 

 ployed for causing adhesion between surfaces of paper, 

 and for thickening colors in calico-printing. Gum Arabic, 

 when burned, leaves about 3 per cent of ash, chiefly car- 

 bonates of lime and potash ; it is, in fact, a compound of 

 lime and potash with Arabic acid. 



Aratoic Acid is obtained pure b.v mixing a strong solution of gum 

 Arabic with ciilorhjdric acid, and adding alcohol. It is thus pre- 

 cipitated as a millv-white mass, which, when dried at 212°, becomes 

 transparent, and has the composition Cia Hja On- 



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