244 Observations on the Absorption of {Ocr. 
bable that the true absorption of oxygen gas, like that of the other 
gases, is completed in 36 hours; that this absorption amounts to 
91 volumes; and that during that time no perceptible quantity of 
carbonic a¢id gas is formed. On this account, in the subsequent — 
details into which I shall enter I shall take no farther notice of this 
formation of carbonic acid gas. 
2. Influence of Water on the Absorption of Gases by Box-wood 
Charcoal. 
The results above stated suppose and require that the charcoal 
before and during its action on the gases be dry. If the charcoal, 
after being cooled under mercury, be moistened with water, the 
absorption of all those gases that have not a very strong affinity for 
water is distinctly diminished. * ’ 
* Box-wood charcoal cooled under mercury, and drenched in water 
while still under mercury, is only capable of absorbing 15 volumes 
of carbonic acid gas; although, before being moistened, it could 
absorb 35 volumes of the same gas. The moistened charcoal like- 
wise takes a longer time to complete its absorption than the dry 
charcoal. Thus charcoal that when dry absorbs 35 volumes of car- 
bonic acid gas in 24 hours, requires when moistened with water 14 
days in order to absorb 15 volumes. 
The effect of moistening charcoal upon its power of absorbing 
gases becomes more striking when we allow dry charcoal in the first 
place to saturate itself with a gas, and then bring it through mer- 
cury into a jar filled with mercury, and containing a quantity of 
water about equal to the bulk of the charcoal. In 48 hours the 
examine the residual gas. I found it as pure as before the introduction of the 
charcoal, and containing no traces of carbonic acid gas. It is, however, probable 
that carbonic acid gas had been formed, and that it was contained in the pores of 
the charcoal. It islikely that the diminution would have gone on till the absorption 
of gas amounted to 35 volumes, as that is the quantity of carbonic acid gas ab- 
sorbed by dry charcoal; and that, after this, free carbonic acid gas would have 
been formed. But as 20 years might have elapsed before a notable quantity of 
carbonic acid appeared, when the experiment was conducted in this way, Ishort- 
ened the process, by introducing moist charcoal instead of dry. The consequence 
was, that in about a year part of the surrounding oxygen gas was changed into 
carbonic acid gas at the common temperature of the atmosphere. We shall see 
hereafter that one volume of box-wood charcoal quenched in water absorbs only 
15 volumes of carbenic acid instead of the 35 which are absorbed by one volume 
of dry charcoal, A volume of wet box-wood charcoal put into oxygen gas stand- 
ing over mercury diminished the volume of the gas for 10 months, and ill the 
diminution amounted to 15 volumes, and during this time no carbonic acid could 
be detected in the residual gas. But after the absorption ceased, carbonic acid 
began to appear, and in four months amounted to half a volume. The charcoal 
itself being plunged into lime-water rendered it very milky. 1 thought I detected 
2 trace of carbureted hydrogen gas likewise in the residual gas, but am not quite 
sure, as the quantity was so small as to be within the limits of error in the experi- 
ments. , i 
* Atleast with regard to charcoal, which has the property of absorbing a great 
deal of gas. With regard to some other bodies which have the property of ab- 
sorbing but little gas, their power of absorbing gas is rather increased by moisten- * 
ing them with water. 
