i g6 Mr. J. Davy's Account of some Experiments on the 
of Proust, is to the chlorine as 7.5 to 34.4; and the arsenic 
being as 21.9, the oxygene, from the analysis of the same che- 
mist, is to the chlorine as 7.3 to 33.6. The analyses of the 
oxides of the other metals being at variance with those of the 
chlorine combinations, I was induced to make the following 
experiments, with the hope of discovering the cause of the 
difference. 
100 grains of lead, which had been precipitated from the 
nitrat of lead by zinc, were dissolved in nitric acid and thrown 
down by carbonat of potash. This precipitate of carbonat of 
lead was well washed and dried and heated to dull redness 
for a quarter of an hour in a platina crucible ; by this treat- 
ment all the carbonic acid was expelled ; the remaining yellow 
oxide weighed 107.7 grains, and it dissolved in muriatic acid 
without effervescing, and without affording any residue of 
brown oxide. Hence the yellow oxide of lead appears to con- 
tain 7.15 per cent, of oxygene. And this proportion of oxy- 
gene in the oxide compared with that of chlorine in plumbane, 
lead being as 97.2 appears to be in the ratio of 7.5 to 33. 8, 
instead of that of 15.6 the estimate of Klaproth, or of 11.2 
the estimate of Dr. Thompson to 33. 8 . Klaproth might have 
been misled by considering the hydrated oxide as a true white 
oxide free from water. 
According to M. Proust the peroxide of antimony contains 
23 per cent, of oxygene, and the protoxide 18.* I have re- 
peated this chemist's experiments ; my results, in which the 
peroxide is concerned, agree with his ; but there is not the 
same concordance in those relating to the protoxide. The 
protoxide I used was either prepared by the decomposition of 
* Journal de Physique, Tom. LV. 
