~e 2S 
On definite Proportions. 461 
ingly as the heat has kept up the boiling of the fluid more 
or less equably. 
If we boil a weakly acid solution of nitrate of the prot- 
oxide of lead in an open vessel, with more lead, we obtain a 
yellow solution, which deposits yellow crystals. I thought 
at first that this might be a double salt, containing two 
acids, and therefore attempted to analyse it with accuracy 5 
but I found that it did not remain always alike, that even 
the same specimen was more or less yellow in different 
parts, and that the portion last deposited contained the ni- 
trite in greater quantity than the rest. This salt was there- 
fore only a contemporary crystallization of the two separate 
salts mixed together. By powdering it, and exposing it to 
the air, it loses gradually its yellow colour, and when dis-~ 
solved in water it leaves some subnitrate behind. If it 
were really a double salt, in which the acids were combined 
each with half of the base, it ought to leave, after ignition, 
68-9 per cent. of the protoxide. But T obtained only from 
67°5 to 68°5 per cent., accordingly as I examined the earlier 
or the later crystallizations. 
I must also mention another phenomenon of the neutral 
nitrite of lead, which it probally exhibits in common with 
the other nitrites. If we concentrate a solution of this salt 
by exposure to heat, the acid becomes more oxygenized ; 
and since the newly-formed nitric acid then finds in the 
salt 1 more of the base than it can saturate, ¢ of the newly- 
formed salt separate as a subnitrate, while 2 remain in the 
solution as a neutral nitrate. When the liquid has acquired 
a certain degree of concentration, at a temperature approach- 
ing to the boiling point, an effervescence takes place, nitrous 
gas is discharged, and subnitrate and subsubnitrate are 
formed. 
The neutral nitrite may therefore be decomposed in two 
ways. Hither the acid is more oxygenized, at the expense 
of the air, and a mixture of 2 of subnitrate and 3 of nitrate 
is formed ; or half of the ammonium of the acid is disengaged 
by the heat, with as much oxygen as is necessary for the 
formation of nitrous gas, and the remaining oxygen changes 
the other half of the ammonium into nitric acid, so that +4; 
of the weight of the nitrous acid escape as nitrous gas, while 
sf; are retained as nitric acid, and form a mixture of } of 
subnitrate and 1 of the subsubnitrate of the protoxide of 
lead. The fluid remains, as long as it is boiling, tolerably 
clear; but when it cools, the subsalts are deposited. The 
same happens also when the solution is diluted with water. 
The transformation of the nitrous into nitric acid, by dit- 
erent 
