22 Improvements in Physical Science [JAN 
the subject; but they confined themselves chiefly to the action of 
charcoal, and their experiments were neither sufficiently varied nor 
precise to throw much light on the subject, far less to enable us to 
form a theory explaining the nature of that absorption. But M. de 
Saussure of Geneva, one of the most accurate chemists of the 
resent day, has lately turned his attention to the subject, and 
published a most elaborate set of experiments. He did not confine 
himself to charcoal, but tried a number of other solid substances, 
and varied his experiments so much as to enable him to give us a 
very satisfactory theory of these absorptions. I first saw this im- 
portant paper in Gilbert’s Annalen der Physik, and immediately 
translated it for the Annals of Philosophy. It lay some time by me 
before I could find room to insert it ; but its importance was such 
that I was unwilling to withhold it from my readers, and therefore 
substituted it in place of the customary biographical article with 
which the numbers of the Annals of Philosophy usually commence, 
It will be found in the fourth and fifth numbers of our sixth volume. 
The general result of De Saussure’s experiments leads to the 
conclusion, that the absorption of gases by porous solid bodies 
depends upon the same cause as the capillary attraction of liquids: 
Chemical affinity doubtless has its effect, as it has also upon. capil- 
lary attraction, Charcoal, meerschaum, ligniform asbestus, reck 
cork, hydrophane, quartz, sulphate of lime, mineral agaric, hazel- 
wood, mulberry, fir, linen thread, wool, and raw silk, were the 
solid bodies employed, and all of them have the property of ab- 
sorbing gases. 
Charcoal absorbs the most gases, and the proportions absorbed 
by the other bodies are nearly in the order in which they have been 
named. Each of these substances absorb a determinate quantity of 
every particular gas; but the order is not the same for the different 
solid bodies indicating the action of chemical affinity. Thus char- 
coal absorhs more nitrous oxide than carbonic acid gas; but meer- 
schaum absorbs more carbonic acid gas than nitrous oxide. The fol- 
lowing table exhibits the nnmber of volumes of the different gases 
absorbed by dry box-wood charcoal. 
Volumes, Volumes, 
Ammoniacal gas...... 90 Olefiant gas....... 35 
Muriatic acid ........ 85 Carbonic oxide .... 9°42 
Sulphurous acid ...... 65 ORV EE as occas aise.) es 
“dulphureted hydrogen . 55 PRZORES Ve he's 3 (elo 
Nitrous oxide........ 40 Oxy-carburetedhydr. 5 
Carbonic acid........ 35 Hydrogen... . ss csigo 
Water diminishes the power of solid bodies to absorb gases. And 
when a solid body is saturated with a gas, the addition of water 
disengages a portion of this gas. During the absorption of gases 
by solid bodies, heat is disengaged, owing obviously to the conden- 
sation of the gas in the pores of the solid body. Thus the density 
