1 22 
METALLIC OXIDES. 
The Oxides of Tin. 
Oxides of tin. We now come to a metal which has long been known, and, 
for that reason, has not been examined with the same care as 
those to which we owe our knowledge in the discoveries of 
the present day. Notwithstanding I have taken much trouble 
in order to determine the degrees of the oxidations of tin, as 
well with regard to their number as to their properties, I cannot 
venture to hope I have exhausted this subject, but that much 
still remains to be explained by future experiments. 
We find, amongst the oxides of tin, the same general cha- 
racters as belong to antimony, but with differences, which begin 
a transition of metals, from electro-negative to electro-posi- 
tive. 
In order to ascertain whether tin possesses a suboxide or not, I 
endeavoured to examine the black film which is formed on the 
surface of melted tin. To procure this black substance, I exposed 
some extremely thin leaves of tin to a very high temperature, 
taking care not to melt them. They became blackened, and, when 
it appeared to me, that the leaves were entirely covered, I took 
them from the fire. On examining them, I found the oxided 
film so extremely fine, that it could not be separated from the 
metallic tin. I then exposed the leaves again to a continued 
heat, but it appeared that the film had prevented the air from 
coming into contact with the metallic parts. When the leaves 
were heated to nearly a red beat, they burnt brightly, and left 
a whitish powder. Not being able to separate the black oxide 
produced in this manner, I endeavoured to procure the oxide 
of tin, oxidum stannossum, which the elementary books 
describe as white, in order to compare it with this black and 
combustible oxide, and to discover, by that means, if the latter 
was actually in a degree of oxidation inferior to the stanneous 
oxide, oxidum stannossum. I then dissolved pure tin in con- 
centrated muriatic acid - } the solution was precipitated by the 
carbonate of potash, and I washed the precipitate on a filtre 
with boiling water. It was perfectly white, and preserved its 
colour after being dried. Some chemists assert, that the caustic 
alkali precipitates the stanneous muriate of a grey colour. 
I have not found it so $ the caustic alkali readily produces a 
whit 
