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 iz 
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.— 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 
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 comfrey; 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, 
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. 
Arabic Acid is obtained pure by mixing a strong solution of gum 
Arabie with chlorhydrie acid, and adding alcohol. It is thus pre- 
cipitated as a milk-white mass, which, when dried at 212°, becomes 
transparent, and has the composition Cy Hyg Ox. 
