VEGETABLE SUBSTANCES. 183 



culiar principles ; but it would exceed the bounds 

 of this work to describe them all in detail. The chief 

 among them are suber, or a peculiar substance found 

 in cork ; asparagin, found in asparagus ; meduttin, 

 from the pith of the sunflower ; fungin, the fleshy 

 part of mushrooms, &c. 



Vegetables also contain several acids ready 

 formed. Vegetable and animal acids differ from 

 the others essentially. They always contain car- 

 bon and hydrogen : some of them contain azote, 

 and generally, though perhaps not always, oxygen. 

 They do not seem capable of combining with dif- 

 ferent proportions of oxygen only, but whenever 

 the quantity of this principle changes, that of the 

 rest changes also. 



Tartaric acid. Tartar, or cream of tartar, is a 

 substance found in an impure state, in crusted on 

 the bottom and sides of wine casks : when purified 

 by solution and filtration, it is sold for use. This 

 salt, which is soluble in water, consists of tartaric 

 acid and potash ; it is therefore tartrate of potash. 

 Tartaric acid when crystallized is imperfectly trans- 

 parent, white, and does not deliquesce in the air. 

 It is soluble in water. It combines with alcalies, 

 earths, and metallic oxides, and forms tartrates. 



Oxalic acid, so called from being first obtained 

 from oxalis acitosella, or wood-sorrell. It is also 

 called the acid of sugar, because obtained from 

 sugar by the nitric acid. It is proper that every 

 one should know that oxalic acid is a deadly poison, 

 and that many persons have lost their lives by 

 mistaking it for Epsom salts, which it resembles. 

 It is much employed for cleaning boot-tops and 

 leather, and also by the calico-printers. 



Malic acid was first found in the juice of apples. 

 It exists also in many other vegetables. This acid 



K 3 



