534 ? Intelligence and Miscellaneous Articles, 
state and not melted by too strong a heat. It is not the lead alone, 
but also the oxide of chrome, which absorbs oxygen. If oxide of 
chrome alone be heated in oxygen gas, it is not converted into 
chromic acid; but this takes place, as is well known, if an alkali be 
present. I therefore consider that oxide of lead has the same elFect 
in this respect as an alkali. In order to obtain an intimate mix- 
ture of oxide of chrome and oxide of lead, I endeavoured by means 
of heat so to decompose the chromate of lead, that all the chromic 
acid should be converted into oxide of chrome. The temperature 
must be very high for this purpose, and it requires a long time be- 
fore any considerable quantity of oxygen can be driven out of this 
salt. 1'409 gramme was fused in a very thin platina crucible b}/- 
the strongest heat of a spirit-lamp before any appreciable loss took 
place. 0*057 grm. were then given off equal to 4 per cent, which is 
nearly j^gths of the whole quantity contained in it ; this would be 
3*9 per cent. It is therefore very probable that at first the chro- 
mate of lead is so decomposed that basic chromate of lead and 
oxide of chrome are formed. 
2 (Cr O 3 Pb O) = Cr O 3 Pb^ -h Cr O 1 ^ + O 1 ^. 
The compound obtained in this manner I considered very favour- 
able for the conversion of chromic oxide into chromic acid. I heated 
it, and passed a stream of oxygen through it. However, to my great 
surprise, not the least alteration took place, and I found no increase 
in weight. 
In the oxidation of the reduced salt, oxygen must have combined 
with the oxide of chrome, as 6*2 per cent, was in all absorbed, while 
the whole of the oxygen of the oxide of lead in the salt amounts only 
to 4*89 per cent.; and it is not at all likely that even the whole of 
this 4*89 per cent, was absorbed by the reduced lead, as it was for 
the most part fused into small globules, which must have very much 
prevented the action of the oxygen upon it. 
I again fused 2*057 grammes of chromate of lead in an aether lamp 
supplied with oxygen: after a long- continued heat it lost 0*091 
grm. or 4*4 per cent. The reduction was in this case carried on 
rather further than the conversion into basic chromate of lead and 
oxide of chrome. When, however, oxygen gas was passed over 
this compound very little of it was absorbed. 
I at last prepared an intimate mixture of oxide of chrome and 
superoxide of lead ; this was heated to redness and oxygen gas 
passed through it. This compound contained 0*445 grm. oxide 
of chrome. When the absorption had terminated, the increase of 
weight was found to be 0*066 grms. The colour was changed from 
green to brown. 0*455 grm. oxide of chrome contain 0*132 oxygen, 
therefore just double the quantity it had taken up. Therefore one 
atom of oxide of chrome upon heating with oxide of lead had com- 
bined with 1 ^ atom of oxygen. 
This gives 2 Cr 3 O -j- 2 Pb O -h 1^0, or, 
Cr O 3 Pb, O, -b CrOli 
It is therefore the same compound which is formed when chromate 
of lead is fused by itself. 
It follows from the foregoing ex])eriments : 
