456 On definite Proportions. 
sible without a decomposition of a part of the nitrous acid, 
aud consequently without evolution of gas. 
On this subject I was satisfied by means of the following 
experiment #—TI put into a small glass flask 12 ‘¢ grains’’ of 
nitrate of the protoxide of lead, and 10 gr. of lead seer” 
thin. I filled the Hask with boiled water, and introduced into 
its mouth a tube for the reception of gas, filled also with 
waier. The flask was slowly heated over a spirit lamp, until 
the fluid came near to the boiling point. The lead began 
by degrees to be dissolved, and a number of very small 
bubbles rose from it, as from a conductor acting on water 
in the galvanic circuit. I did not suffer the fluid to boil; 
and in this manner a quantity of gas was collected, which 
was not condensed in cooling. Finally I made the fluid 
boil, and stopped the experiment, when the lead began to 
be covered with a yellow brown pellicle. It was found 
that 7°64 gr. of lead had been dissolved, and 1°8 cubic 
inch of gas had been disengaged; the thermometer stand- 
ing at 12° [54°]. When the gas was mixed with oxygen 
gas, it was condensed into red vapours, which were wholly 
absorbed by water; consequently it was nitrous gas. In 
other experiments, in which I performed the solution of the 
lead in retorts with tubulated receivers luted to them, the 
oxygen gas of ihe receiver was absorbed, and the water that 
distilled over was very perceptibly acid. Consequently the 
decomposition of a small part of the nitrous acid, while the 
Jead is dissolved in the nitrate of the protoxide, is put 
beyond all doubt by this experiment. 
{ was in hopes of being able to determine the quantity of 
the jead dissolved more accurately, by allowing the solution 
to boti upon more lead than it ought to be able to dissolve 
according to the computation. For this purpose I poured on 
12°5 ‘‘ grains” of very pure lead hammered thin, in a very 
long-necked flask, a solution of 10 gr. of nitrate of the prot- 
oxide of lead in 500 gr. of water, and boiled the mixture 
for 1% hours. The orifice of the flask was closed with a 
cork, having a glass tube fixed in it, which allowed the 
gas to pass through. After twelve hours, the solution was 
poured into a bottle, which it nearly filled, and then was 
loosely stopped. To my great surprise, only «85 gr. of the 
lead were left undissolved. The solution, when poured off, 
crystallized in the form of small scales of a brick colour, 
and the fluid, which remained behind, had lost its colour. 
It was boiled down to 3, and then, being put into a bottle, 
deposited two different groups of crystals. The one was 
the yellow subnitrite of the protoxide of lead, already de- 
senibed ; 
