On definite Proportions. 453 
water is diminished by this addition. The colour disap- 
peared immediately, and nitrate of the protoxide of lead 
was crystallized in abundance. But these solutions mixed 
with nitric acid had always so suffocating a smell of nitrous 
gas, without however exhibiting red vapours, that I was 
obliged to remove them out of the laboratory. I now poured 
nitric acid on a portion of the yellow salt, and gently heated 
the mixture: in the mean time small bubbles of gas were 
disengaged, which, even at the bottom of the vessel, before 
they came in contact with the air, appeared of a red colour. 
The acetic acid produced the same appearance. It was there- 
fore beyond all doubt that this yellow salt contained a com- 
bination of nitrous acid with the protoxide of lead, from 
which it probably derived the yellow cojour. 
I immediately determined to examine how the oxygen of 
the nitrous acid was related to that of the base, and if this 
relation would not afford a new proof my idea of the com- 
position of nitrogen. For this purpose I boiled in a sinall 
glass flask a solution of 20 grammes of nitrate of the prot- 
oxide of lead with 19°4 gr. of thin hammered lead ; that 
is, with precisely as much as the salt already contained. 
After some hours, the lead was completely dissolved, and 
the solution had assumed a full yellow colour. While it 
was cooling, it congealed completely into a scaly yellow 
mass, which allowed a colourless fluid to be pressed out of 
it. The solution had a taste rather astringent than sweet, 
and acted on reddened litmus paper precisely as an alkali. 
This was also the case with the crystals. Acids evoived 
nitrous acid in great quantity from this salt. It is therefore 
a subnitrite of the protoxide of Jead. Hence it appears 
that there must be a distinct neutral combination of the 
nitrous acid with the protoxide: of this I shall speak here- 
after, and first endeavour to ascertain the composition of 
this subsalt. 
The crystals that had been obtained were levigated, well 
dried, then heated in a small glass retort, and at last strongly 
ignited, until no more nitrous gas was disengaged. The 
salt d'd not melt in the heat. It emitted partly gaseous, 
partly fluid, red, smoking nitrous acid, and consequently 
contained some water of crystallization. ‘The part of the 
oxide of lead, which had not been fused, was of a fine light 
yellow, and weighed, in different experiments, 79°5, 79°75, 
to 80 per cent. of the salt which had been employed. 
If we consider the nitrous acid as composed of nitrogen 
and oxygen, it contains for 6371 parts of oxygen 39°5 of 
nitrogen. If, on the contrary, we regard it as composed 
Ff3 
. 
of 
