872 SAI.ICYL. 



The bichromate of potash and salicin are intimately mixed,, 

 and after pouring over them two thirds of the water, the whole 

 being well agitated in the retort, we add all at once the sul- 

 phuric acid previously diluted with the remaining third of the 

 water, and agitate again. A feeble reaction slowly manifests 

 itself, accompanied by a slight disengagement of gas, which 

 lasts about half an hour or perhaps three quarters of an hour, 

 when an ounce is employed for each part ordered ; at the same 

 time the liquid assumes an emerald tint and becomes warm. As 

 soon as that reaction has ceased, the retort is placed upon the 

 fire and moderately heated. The water vapour carries over the 

 salicylous acid, which separates after some time. It is purified 

 by washing it with water and rectifying from chloride of calcium. 

 From half a pound of salicin Dr. Ettling obtained two ounces 

 of the oil.* 



Salicylous acid is an oily inflammable liquid, colourless or 

 slightly yellow, having a burning taste, and agreeable aromatic 

 odour; of density 1. 1 73 1, becoming solid at 4 (Loewig) ; it 

 boils at 385.7 (196.5 centig.) when prepared from salicin 

 (Piria), while the oil from the flowers of the Spiraea boils at 

 359.6 (182 centig.), according to Ettling. The density of its 

 vapour is by observation 4276 ; by calculation 4260, or the 

 same as that of benzoic acid. It dissolves easily in water, and 

 may be mixed with alcohol and ether in all proportions ; its 

 solution in water reddens tincture of litmus, and discolours it 

 after the lapse of some time. It is decomposed by sulphuric 

 acid 5 also by chlorine, one atom of hydrochloric acid being 

 formed and eliminated, and one atom of chlorine substituted for 

 the hydrogen, as usual. When heated with an excess of 

 hydrate of potash, salicylous acid is converted into salicylate of 

 potash, with an escape of hydrogen gas. Potassium also when 

 slightly heated in it, gives the same products. 



Salicylous acid is recognised by producing a violet colour with 

 salts of peroxide of iron, which disappears after some time. In 

 the salicylites, the atom of hydrogen of the formula of salicylous 

 acid is replaced by a metal. The salts of the fixed alkalies 



of salicylous acid in the state of vapour, which is the same as that of benzoic 

 acid. 



* Liebig's Annalen xxxv, 241 ; or Annales de Chimie, &c., 3rae Se"rie, t. 1, p. 490. 



