74 ORGANIC CHEMISTRY. > 



has been removed which is soluble in water, alcohol, and dilute 

 solutions of alkalies and acids, contains nearly half its weight of 

 charcoal, or carbon, and oxygen and hydrogen, in the proportions in 

 which they constitute water, to the amount of the remainder. 

 Some of the various products which it affords, or into which it is 

 convertible, are — 



Vinegar, or Acetic Acid. — When wood is decomposed by being 

 subjected to a high temperature, among other products, acetic acid 

 is obtained. Manufactories have been established, on a scale of 

 considerable magnitude, for the purpose of obtaining this acid by 

 the distillation of wood. In fact, from this source is derived nearly 

 the whole of the acetic acid consumed in the manufacture of sugar 

 of lead, acetates of alumina and iron, and for the other demands of 

 the arts. The small branches of trees, which would otherwise be 

 of little value, excepting for fire wood, are submitted to distillation 

 in iron retorts ; the gaseous products are allowed to escape, and the 

 vapours are condensed in tubes of earthenware, surrounded by 

 water. Tar, and very weak acetic acid, are the principal products. 

 The tar is separated, as much as possible, by mechanical means^ and 

 the acid saturated by lime, added in considerable excess. In this 

 process, the acetic acid combines with a portion of the lime, form- 

 ing a neutral salt, which is dissolved by the water present ; while 

 the remaining tar combines with the excess of lime, forming an 

 insoluble earthy soap. The solution of acetate of lime is evaporated 

 to dryness, and, after being mixed with a proper proportion of sul- 

 phuric acid, is submitted to distillation. The sulphuric acid com- 

 bines with the lime, forming sulphate of lime, while the acetic acid, 

 being volatile, distils over. 



Pyroxylic Spirit is formed simultaneously with acetic acid, during 

 the distillation of wood. It resembles ether in its volatility, inflam- 

 mability, and in its power of dissolving Indian rubber. 



Formic Acid is the acid with which the bodies of ants are so 

 strongly impregnated, and which they emit so copiously, when irri- 

 tated, as to affect the eyes. It is the pleasant flavour of this acid 

 which has recommended ants to the taste of some entomological 

 palaticians — see Kirby and Spence. Now, if instead of submitting 

 wood to distillation alone, sulphuric acid and black oxide of manga- 

 nese be added, formic acid, or the acid of ants, is obtained. 



Malic Acid is found in the apple and in several other fruits, and 

 in the juice of the house-leek. If wood be digested with nitric acid, 

 a little diluted, and in a proportion not too large, an acid identical 

 with the malic, or acid of apples, is produced. 



