Mons. R. Piria on the Combinations of Salicyle. 213 



drops should be collected, and purified by being distilled 

 with chloride of calcium. It is important that no more acid 

 be used than is here prescribed, otherwise a quantity of formic 

 acid is produced, and a corresponding diminution in the 

 quantity of hydruret of salicyle ensues. 

 The hydruret consists of 



Carbon. Hydrogen. Oxygen. 



Salicyle = 14 5 4 



Hydrogen... 1 



Atomic weight . . 14 6 4 



Hence it appears that hydruret of salicyle is isomeric with 

 hydrated benzoic acid ; and it is not a little remarkable, that 

 the density of its vapour is identical with that of the latter 

 acid, as determined by Dumas, being 4* 276. It therefore 

 consists by volume of 



7 volumes vapour of carbon 



3 ' hydrogen 



1 oxygen 



The hydruret of salicyle may be considered as a true hy- 

 dracid, with a compound base like hydrocyanic acid ; like 

 that compound it combines with metallic oxides, its hydrogen 

 forming water with the oxygen of the oxyd, and a salicide of 

 the metal results. The metallic salicides are isomeric with 

 the corresponding anhydrous benzoates of the oxides, thus 

 placing M for an atom of a metal, and M + O for one of a 

 metallic oxide ; a given benzoate and salicide will consist of 



Carbon. Hydrogen. Oxygen 

 Benzoate= (14 + 5 + 3) + (M + O) 

 Salicide = (14 + 5 + 4) + M 



So that the hydruret of salicyle bears the same relation to hy- 

 drated benzoic acid as oxalic acid, according to the view of 

 Dulong (2 C, 4 + H) does to the generally received view of 

 its composition at the present day, or (2 C, 3'0 + PI O). 



Metallic Salicides. 

 The salicide of potassium may be very readily prepared, 

 by mixing the hydruret of salicyle with a strong solution of 

 pure potass. On shaking the mixture, a considerable quantity 

 of salicide of potassium separates in small yellow crystals 

 from the supernatant alkaline fluid. These crystals must be 

 collected, freed from adhering moisture by pressure between 

 folds of bibulous paper, and dissolved in alcohol ; by crystal- 

 lization numerous well-defined square tables of the salicide 

 are obtained. This salt is readily soluble in water and al? 



