70 HOW CROPS GROW. 



of the filtrate add one drop of strong sulphuric acid, and boil a few 

 minutes. Test with iodine, which will now prove that all the starch is 

 transformed. 



Not only heat, but likewise acids and ferments produce 

 dextrin from starch, and also from cellulose. In the 

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

 an ingredient of malt liquors. It is often contained in 

 the animal body. Limpricht obtained nearly a pound of 

 dextrin from 200 Ibs. of the flesh of a young horse. Ann. 

 Ch. Ph., 133, p. 295. 



The chemical composition of dextrin is the same as that 

 of cellulose, starch, and inulin. 



The 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 



O 



best known are Gum Arabic, or Arabin the gum of the 

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

 sora Gum, or Bassorin ; and the Vegetable Mucilage of 

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

 seeds, as those of flax and quince, 



Arabin. 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, 

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

 when burned, leaves about 3&quot; per cent of ash, chiefly car 

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

 lime and potash with Arabic acid. 



Arabic A&amp;lt;*il is obtained pure by mixing a strong solution of guni 

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

 cipitated as a milk-white mass, which, when dried at 212&quot;, becomes 

 trau .-parent, and has the composition C ]2 H aa O,,. 



