272 
POWER OF LITHARGE, ETC. 
different periods of the process, and that this gas had a 
tendency to disengage itself at the instant the solidification 
took place. The facilities he was kind enough to grant me, 
enabled me to collect, carefully, the litharge, in different 
degrees of purity, and at various stages of the process • I 
also collected the gas when it was disengaged. The experi- 
ment completely confirmed the suspicions of M. Thenard, 
so far as regards the solution of the oxygen ; for the gas 
collected offered me the properties of nearly pure oxygen. 
Its analysis indicated from S2 to 90 per cent, of oxygen. It 
cannot be said with certainty that the proportion of nitrogen 
was not due to the accidental presence of a small quantity 
of air; in fact, when repeating the experiment in the same 
manner upon silver taken out of the refining cupel, I did 
not find more than 90 per cent, of oxygen absorbable by 
heated phosphorus. 
The quantity of oxygen dissolved in a given weight of 
litharge is too considerable to enable us to admit that the 
silver contained in the litharge could be the solvent of the 
gas : this proportion was not less than 50 cubic centimetres 
per kilogramme, notwithstanding the losses inseparable from 
the mode of operating. Besides, the last quantities of the 
litharge, and the richest did not contain more than 0.001 to 
0.0015 of silver. 
It appears to me, therefore, an established fact that lith- 
arge, a substance incapable of oxidation at the temperature 
of the furnace, might, under the influence of a current of 
air, dissolve the oxygen after the same manner as silver, 
and act as most liquids do when in contact with gases. 
The black, or impure litharge is, according to my experi- 
ments, unfit for dissolving the gas; at least the quantity 
found was so trifling, that we may be allowed to consider 
its presence as accidental ; analysis has also indicated oxy- 
gen and nitrogen, in nearly the same proportions as in the 
air. This circumstance will not be surprising, if we reflect 
