M ETALLIC OXIDES . 
3 30 ' 
Oxides of tin. the oxide at a maximum with plumbiferous glass, a combina- 
tion of the intermediate oxide with the glass ? 
I ought, lastly, to remark, that the oxide at a maximum, is 
frequently obtained perfectly white. For example, if the filings 
of tin, and the red oxide of mercury, are mixed together, and 
exposed to fire, or if the purple powder of cassius be ignited, 
and the gold afterwards dissolved by the nitro-muriatic acid. 
This white oxide does not change its colour when ignited in 
the fire, and it is insoluble in muriatic acid, which receives 
from it a yellowish tinge. I imagined at first, that this oxide 
was in a still higher degree of oxidation, but I have not been 
able to discover whether the tin gains more weight when oxided 
by the oxide of mercury, which gives this white oxide, than 
when it is oxided by nitric acid. The only difference between 
the yellow and the white oxide, when both are at a red heat in 
the fire, appears then to consist in a different aggregation, 
exactly as Sef&trom has proved, that the black precipitate, 
which is obtained from corrosive sublimate, by means of sul- 
phureted hydrogen gas, contains the same constituent parts in 
exactly the same proportion as cinnabar, and, consequently, 
the colour is to be attributed to' the difference of aggregation. 
Combinations of the Oxides of Tin with the saline bases. 
I have already mentioned, that the hydrate of the yellow 
oxide colours the paper of tournesol red, but that the oxide 
that has been through the fire, loses this quality. I have reason 
to suppose, that it is the same with intermediate oxide. If we 
add to this, the property possessed by these oxides of produc- 
ing with the alkalies, combinations which are soluble in water, 
we shall have plausible reasons to consider all these oxides as 
acids, exactly as we have already done, with the oxides of anti- 
mony. But, as on the other hand, these oxides produce, with 
the acids, salts which are quite neutral, and are the weakest 
amongst the electro-negative bodies, it is difficult to decide 
what name should be given them in preference. In the man- 
ner in which these oxides comport themselves with the alkalies, 
and saline bases, they so much resemble each other, that I 
have not been able, in my experiments, to discover any diffe- 
rence, except that the combinations of the intermediate oxide 
with 
