{ 35 ] 
V. On the Production of the brown Oxide of Lead, under 
Circumstances which have not been hitherto observed. 
By M. CHEVREUL*. 
I+ is well known that lead is susceptible of combining 
with oxygen in various proportions, and of forming Ted, 
brown, and yellow oxides which have not the same affinity 
for the acids. It is from this affinity of lead for different 
quantities of oxygen, and from the disposition of the yel- 
Jow oxide to form salts, that the cause of the phenomena 
which we have observed must be deduced. When we mix 
red oxide of lead with nitric acid, we may observe that one 
rt of the oxide is brought to the state of yellow oxide, 
which is dissolved, while the other part is combined with 
the oxygen abandoned by the former to form brown oxide, 
which is not dissolved. Hitherto only two cases have been 
remarked, in which the brown oxide of lead was produced ¢ 
that to which I have alluded, is where the red or yellow 
oxide of Jead is in contact with the oxygenated muriatic 
acid: accident brought another under my notice, which £ 
shall now communicate. I had been treating some plate- 
glass (crystal) reduced into a fine powder with nitric acid, 
with a view of analysing it. The matter which was insolu- 
ble in the acid had been washed and calcined, and then 
heated in a platina crucible with three times its weight of 
otash. When we diluted with water the mass which had 
eas fused, an alkaline solution was obtained, plenty of 
silex and yellow oxide of lead, and it was ‘remarked that 
the platina spatula which remained in the crucible during 
the operation contained at its extremity a button of an 
alloy of platina and lead; the bottom of the crucible was 
covered with a cimilar alloy. The alkaline mass diluted. 
with water deposited a brown crystallized powder which 
had a metallic appearance : 1 took it at first for iridium 5 
bat afier haying washed it, and poured nitric acid upon it, 
the latrer assumed a fine red colour, which it lost by filtra- 
tion: as the brown oxide of lead presents the same phe- 
nomenon, [ thought that the brown powder might be this 
very oxide. The following experiments proved that | was 
right: this powder exposed to heat in a glass tube was re- 
duced to litharge with effervescence; when treated with 
the muratic acid, it exhaled abundance of oxymuriatic gas, 
and formed muriate of lead, which crystallized in brilliant 
flakes. According to these results, it 1s evident that in the 
* Annales de Chimie, tome lxxxiv. p- 315. R 
C3 treatment 
