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SELECTED ARTICLES. 
The hyduret of salicyle should be a combination of salicyle 
with an equivalent of hydrogen, and have for its formula, 
C 28 H 10 O 4 4-H 2 . This substance is a true hydracid of a compound 
radical, as hydrocy anic acid is, and metallic oxides act upon both 
inexactly the same manner. One equivalent of the hydrogen 
of the hyduret unites with the oxygen of the oxide, while the 
salicyle combines with the metal. Thus, we can perceive why 
the isomerism between benzoic acid and the hyduret of salicyle 
should be extended to their saline combinations; or in other 
words, why the anhydrous benzoates are isomeric with 
the correspondent metallic salicides, C 28 H 10 O 3 -f-MO, being 
+ C 28 H 10 O 4 + M. 
From these facts, it results that the hyduret of salicyle is to 
hydrated benzoic acid as the oxalic acid, C 4 Q 4 -f H 2 , according 
to the views of M. Dulong, is to the same body as at present 
considered C 4 3 H 2 0. 
Metallic Salicides. 
Salicide of Potassium. — This combination maybe procured 
with great facility. It is sufficient to mix the hyduret of sa- 
licyle with a very concentrated solution of potassa, nearly 45° 
B. On stirring this mixture with a glass rod, the oil assumes 
the form of a crystalline mass, which separates from the excess 
of alkaline liquor. These crystals should be rapidly express- 
ed between bibulous paper, and dissolved in a small quantity 
of hot alcohol. On cooling, the solution will deposit the sa- 
licide in square tables of great regularity. 
The salicide of potassium is of a beautiful golden yellow 
color, greasy to the touch, very soluble in water and alcohol, 
and has an alkaline reaction. When very dry, it is not altered 
by the air ; but in the moist state, it begins in a few moments 
with green and finally with black spots. This alteration soon 
extends to the whole mass, which finally becomes as black as 
soot. I shall soon have occasion to recur to the nature of this 
alteration. 
Carbonic acid does not alter the salicide of potassium, either 
