. 
: 
| 
1815.] the Gases by different Bodies. i) 
-When.a piéce of box-wood or beech charcoal free from air is 
exposed to common air, it absorbs more oxygen than azote,’ so that 
the air is injured by it; but not much, as the difference between the 
quantity of these gases absorbed by charcoal is not great. Hence 
that this consequence, which Messrs. Rouppe and Norden deny, 
may take place, the volume of residual air, in comparison of that of 
the charcoal, must be small. 
8. Simultaneous Absorption of various Gases ly different Bodies.’ 
Im general all porous bodies exhibit the same appearances in 
respect to the mutual expulsion and condensation of the gases 
coming in contact with them as charcoal does. Yet these expul- 
sions may take place in an opposite order when the affinity of the 
body for the gases is different. In this respect the results are 
striking which meerschaum, ligniform aslestus, adhesive slate of 
Mesnil Montant, and Saxon hydrophane, give when they are brought 
in contact with mixtures of carbonic acid * or ammoniacal gas with 
oxygen, hydrogen, or azotic gas. A mixture of the two or three 
last gases requires more attention, and the consequence is not 
always perceptible. As in these experiments it appears of no con- 
sequence whether the porous body be first saturated with one gas, 
and then put into the other; or whether it be put into a mixture of 
the two gases; I shall describe here only the results which I ob- 
tained in the last way, as it is the shortest. The experiments were, 
made in temperatures between 59° and 62°. The same pieces were 
employed in all of them; and each porous body was allowed to 
remain” 24 hours in the mixture before the residual gas was exa- 
mined. as 
Meerschaum in a mixture of Oxygen and Hydrogen Gases. 
~ A volume of meerschaum freed from air was put into 21 volumes 
of gas, one half of which was oxygen, and the other hydrogen. It 
absorbed 0°57 volume of oxygen and 0°44 of hydrogen; therefore 
more of the first than of the last. This is conformable to the order 
of absorption of the gases when not mixed. When we compare the 
bulk which both gases occupy in the meerschaum, with the sum of 
their bulks when single, we perceive that the presence of the oxygen 
has promoted the condensation of the hydrogen gas. 
- The same experiment was made with the adhesive slate of Menil 
ah A volume of this stone absorbed 0°7 of the mixture, 
proportion of each gas absorbed was the same, though the 
stone absorbs more oxygen gas when alone than it does of hydrogen 
gas. The difference was either too small to be perceptible, or the 
citi of the oxygen had promoted the condensation of the 
ydrogen to such a degree as to make its bulk equal to that of the 
* Perhaps the small quantity of carbonic acid which some porous stones, as the 
meerschaum of Natolia, contain, is only accidental, or what the water in them is 
able to retain by means of capillary attraction, : 
Vox, VI. N° V, Y 
