264 On the Combinations of the yeliow Oxide of Lead 
matrass as evaporation took place. ‘The liquor gradually became 
of a fine yellow, and after two hours boiling the colour was at its 
maximum of intensity: subsequently it gradually diminished, 
and ended by entirely disappearing. There was deposited in the 
course of the operation a white substance which resembled hy- 
drate or carbonate of lead. After twelve hours boiling, the ni- 
trate apparently having no more action on the metal, I decanted 
the liquor hastily into a vessel, which I shut carefully: the lead 
when dried weighed 0-6 gramme: there was therefore 5:4 gr. 
of lead dissolved by 4 gr. of nitrate. This result is widely dif- 
ferent from Mr. Thomson’s, who says that 100 grains of nitrate 
ean dissolve only 44 grains of lead. 
8. It was easy to determine the proportion of the elements of 
oxide of lead at the minimum, since we knew the quantity of metal 
which had been dissolved by the acid nitrate. But two considera- 
tions prevented me from attempting it: in the first place, the 
yellow colour which the nitrate had assumed in dissolving the 
lead was certainly owing to the solution of this metal; but this 
colour having disappeared, was it not probable that the oxygen 
of the atmosphere was the cause of this discoloration? In the 
second place, the white matter which was deposited did it not 
proceed from the absorption of the oxygen or the carbonic acid 
from the air? In order to appreciate the influence of external 
agents, I repeated the experiment in the apparatus about to be 
described. Ina matrass similar to that which had served for 
the experiment above mentioned, I put water boiled with four 
grammes of acid nitrate and six grammes of lead. | adapted to 
the matrass two glass tubes, one in the form of S, destined to 
replace the water which should be evaporated ; the other doubly 
bent, which fitted into the upper part of a bell-glass filled with 
air. I had put into this bell-glass, which rested in a lime-bath, 
a glass containing a mixture of iron and moistened sulphur. In 
three days the oxygen of the air of the vessels having appeared 
to be absorbed as well as the carbonic acid, | lighted a fire un- 
der the apparatus, and the ebullition of the liquid was kept up 
fourteen hours without interruption. When the water began to 
boil it became yellow: ihe colour fell away in two hours, and 
Jjinally disappeared. There was also, as in the foregoing experi- 
ment, a precipitalion of awhile substance. It was evident from 
this, that the oxygen and the carbonic acid of the atmosphere 
were not the cause of these phenomena. When the operation 
was ended, [ allowed the liquor to rest, and decanted it in a flask 
which was made auite close. I passed water into the matrass, 
in order to detach the white matter from it, as well as the lead 
which had not been dissolved. 
The latter when washed and well dried weighed six deci- 
grammes, 
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