On definite Proportions. 449 
{D) the last-mentioned salt may have been a double com- 
bination of a subnitrate of the protoxide of lead, differently 
modified, with a hydrated protoxide. . 
In order to investigate which was the most probable of all 
these possibilities, I repeated once more the examination of 
this salt. After drying it in a water bath, the water of 
crystallization was driven off in a small glass retort in a 
sand bath. I call it water of crystallization, because the 
salt changed its colour from white to yellow when it was 
expelled. It amounted in one experiment to 2°30, and in 
another to 2°32 per cent. The ignited salt left 88°1 of prot- 
oxide, which was not diminished by fusion. Consequently 
the salt was thus constituted : 
Protoxide of lead 88°10 
Nitric acid .. 9°5(8] 
Water Ve 1108, 232 
The view (C) of the composition of this salt I should 
be least of all disposed to admit, and therefore took care 
to examine all the rest before this. The quantity of the 
protoxide here found contains 6:299 parts of oxygen; that 
of the acid either 6°66 or 8°4112, accordingly as we con- 
sider nitrogen or ammonium as its radical; and the water 
contains 2:05. Since neither of the two numbers belong- 
ing to’ the acid on these different suppositions perfectly 
agrees with the quantity of oxygen contained in the base ; 
I imagined that according to the hypothesis (D) the salt 
might be thus constituted: the nitric acid being combined 
with 2 of the protoxide, and forming with it a subsalt, in 
which the acid contained twice as much oxygen as the 
base, the remaining + might be combined with water as a 
hydrate, in which the oxygen of the water and of the prot- 
oxide might be equal: and the whole might in some mea- 
sure resemble a double salt, in which the oxygen was con- 
tained in the smallest quantity in the water, that of the 
protoxide being three times as much, and that of the nitric 
acid four. This view agrees with the result of the experi- 
ment; but that it probably is not the true one, I am per- 
suaded from the consideration of the other subnitrates, 
which rather seem to indicate, that we must consider the 
acid in these combinations as having nitrogen for iis radi- 
eal, since on this supposition it would contain an equal 
quantity of oxygen with the base, and the water 4 as much. 
That this view of the subject, according to which we are 
to consider the nitric acid as composed of nitrogen and 
oxygen, does not agree with the neutral nitrate of the prot~ 
oxide of lead, if this contains 205°! parts of the protoxide 
Vol. 42. No. 188, Dec, 1813. Ff£ to 
