: the Oxidation of the Metals, Se. 207 
gives a salt which enjoys a great solubility, as well as all 
the metallic salis which take much oxyven. 
{ shal! not extend this memoir further, as I think T have 
related a sufficient number of facts to establish the prin- 
ciple which is the object of it, and to makeraill its conse- 
quences apparent. The propertions of acid im the salts 
depending on the quantity of oxygen which-the bases con- 
tain, it would be desirable if chemists would direct their 
attention, on the oxidation of the metals and on the propor- 
tions most easy to determine, to one or two salts in each 
genus. We should thus obtain the proportions of a great 
number of salts, and we should even have the advantage of 
calculating the Jnmits of those of the aeid salts, in prepor- 
tion as they should approach neutrality more and more. 
For it must be well remarked, that the excess of acid ina 
salt is foreign to the saturation, and that it is only necessary 
to hinder the precipitation of the oxide by destroying its 
force of cohesion. If, in fact, the oxides were very so- 
Juble, they would all form perfectly neutral salts. 
Observation. 
_ When we precipitate a metallic solution by sulphuretted 
hydrogen alone, or consbined with an alkaline base, we 
obtain a metallic sulphuret or hydro-sulphuret. In the first 
case, the hydrogen of the sulphuretted hydroges is com- 
bined with all the oxygen of the oxide, and the sulphur 
forms a sulphuret with the metal. In the second case, the 
sulphuretted hydrogen is combined directly with the oxide 
without being decomposed, and its proportion is such that 
there is enough of bydrogen for saturating all the oxygen 
of the oxide. The quantity of the hydrogen destroyed, or 
capable of being so, depends therefore on the oxidation of 
the metal, in the same wayas the quantity of sulphur which 
may be combined with it. Consequently the same metal 
forms as many distinct sulphurets as it is susceptible of de- 
giees of oxidation in its acid solutions. And as these de- 
grees of oxidation are fixed; we ouzht also to obtain sul- 
phurets with constant proportions, which we may determine 
very easily, according to the quantity of oxygen of each 
metal and the proportions of the sulphuretted hyerozen, * 
I do not pretend that these sulphurets are the only ones 
which we can obtain; but I think that we ought to reeard 
them as the true types of the other sulphurets, so much 
the more as the proportion of the sulphur has an imnie- 
diate relation with the quantity of oxygen which the metal 
_diad, and as the latter determines of itself the proportion 
of acid which is combined with it. 
XXXVI. 4 con- 
