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 wdth the oxygen of the oxyd, and a saticide 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 Mq-O for one of a 
metallic oxide ; a given benzoate and salicide will consist of 
Carbon. Hydrogen. Oxygen 
Benzoate= (14 + 5 + 3) H- (M + O) 
Salicide = (14 + 5 + 4)-f- 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 0 + H) does to the generally received view of 
its composition at the present day, or (2 C, 3’0 + H 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- 
