METALLIC OXIDES, 
127 
colour, but the oxide remained perfectly insoluble. At the Oxides of tin. 
expiration of twelve hours, I opened the bottle ; some oxy- 
muriatic gas escaped with a slight explosion. I then decanted 
the acid, and poured a small quantity of water upon the oxide. 
After the oxide was again deposited, I poured off the water, 
and added a fresh quantity to the oxide which was instantly 
dissolved by it. 
The solution tasted very astringent, was colourless, but not 
perfectly clear. I mixed a portion of the solution, obtained in 
this manner, with a portion of concentrated muriatic acid \ 
which caused an abundant precipitation. On the liquor being 
poured off, the precipitate was again dissolved in water. 
Another part of the same solution was heated in an earthen 
vessel over a lamp of spirit of wine. It coagulated first at the 
bottom and then throughout the whole mass ; and in this state 
it had so much the appearance of albumen, that I should# 
without hesitation, have taken it for that substance, if I had 
not known what it was. This mass had now lost its astringent 
taste, and become acid $ and the precipitate was not re-dissolved 
during the cooling. At this temperature the water had, there- 
fore, precipitated the oxide by separating it from the acid. The 
precipitate washed and heated afresh with the concentrated 
muriatic acid, re-produced the same phenomena which I have 
described. 
These experiments prove, then, that the oxide produced by 
the nitric acid can be combined with the muriatic acid. This 
combination is soluble in water, but it may be separated from 
the water by an excess of muriatic acid, and is decomposed by 
the action of water at an elevated temperature. These pro- 
perties, therefore distinguish this oxide in a decided manner, 
as very different from that found in the spirit of libavius. 
The resemblance of these two oxides as to their external pro- 
perties, the facility with which one appears to be converted into 
the other, without, it being possible to discover them by any 
visible change, and their habitudes with the alkalis being 
exactly the same, makes this disquisition not very easy, and may 
give cause to doubt the accuracy of what I have concluded from 
the experiments here mentioned. Nevertheless, in order to 
put the subject beyond dispute, l mixed some spirit of libavius 
with nitric acid, and evaporated the mixture till it was entirely 
dry. 
