154 VEGETABLE PRODUCTS. 



mingled with water again. Is soluble in Ether, Oil of Tur- 

 pentine, and especially in its own empyreumatic oil. The fami- 

 lies of Urticacece, Euphorbiacese, and Apocyneae yield it. Its 

 uses and importance are too well known to be pointed out. 



Gutta Percha, Cg, H;, is a nearly allied substance to India- 

 rubber, being the hardened juice of the Isonandra gutta, and 

 is imported from Borneo and Singapore. It is harder than 

 caoutchouc when cold, but becomes soft and coheres to itself 

 at a temperature less than boiling water, but it will stick to 

 nothing else. Its most appropriate solvent is Turpentine Oil. 

 Its constitution is the same as India-rubber, and is thought to 

 be only a modified form of that substance. 



300. Vegetable Acids. The acids are numerous, and exist in 

 the juices of the plant in combination with some base, organic 

 or inorganic. They are variously constituted, sometimes con- 

 taining only carbon and oxygen, at other times O, C, and H in 

 various proportions. 



Oxalic Acid, Cg, O3, is extensively diffused in the vegetable 

 kingdom, occurring in the Rhubarb, Oxalis, and many Lichens, 

 usually in combination with lime, though sometimes free. 

 Easily formed by the action of nitric acid on sugar. 



Malic Acid, C4, Hg, O4, occurs in nearly all the sour juices 

 of plants, in connection with other acids. Apple, Plum, Cur- 

 rant, Whortleberry, &c., owe their acidity mostly to this acid. 



Tartaric Acid, with the preceding, is found in most sour 

 fruits. Tamarind, Pineapple, and unripe Grapes derive their 

 sourness mostly from this acid. 



Citric Acid, Cg, H3, Og, is the predominating acid in 

 Lemons and Oranges, and, together with the two preceding, 

 forms the acids of most edible fruits. 



Gallic Acid, Cj^, Hg, 0,o, is found in some plants. Tannin 

 is readily converted into it. 



Tannic Acid, C^g, Hg, 0,2, is a weak acid, found in most 

 plants. It is characterized by its astringent taste, turning solu- 

 ble salts of iron blue or black, and precipitates gelatine. Exists 

 abundantly in Nutgalls, Oak bark, and Chestnut-wood. Con- 

 verts skins into leather. 



Mcconic Acid is one of the acids in opium. Kinic Acid in 

 the Cinchona bark, with Quinine. 



301. Vegetable products containing Nitrogen. — These 

 are in much smaller quantities than many of the preceding, but 

 no less important. Those that make part of our food are 



"What is gutta percha ? Whence obtained ? Its properties ? — 300. How 

 do vegetable acicls exist ? What is said of oxalic acid ? Malic ? Tanarifi ^ 

 Citric ? Gallic ? Tannic ? 



