1815.J the Gases by different Bodies. 333 
between the two takes place, at least within the interval of some 
days. So, for example, notwithstanding the assertion of Rouppe 
and Norden, no separation of water appears when charcoal satu- 
rated with hydrogen at the common temperature is put into oxygen 
gas, or when the experiment is reversed. As little was it in my 
power in this way to unite azotic and hydrogen gases into ammonia, 
or azotic and oxygen gases into nitric acid. 
I shall now give a more particular account of some of these expe- 
riments, which all gave me analogous results, differing from each 
other only in degree. 
Introduction of a piece of Charcoal saturated with Hydrogen into a 
Recewer full of Oxygen Gas. 
A volume of box-wood charcoal, which had absorbed 1-75 times 
its bulk of hydrogen, was at the temperature of 52° put into 20°45 
times its bulk of oxygen gas, which contained ~2~ of azote. The 
charcoal reduced this atmosphere 6°5 volumes.* A thermometer 
brought in contact with the charcoal, when the absorption was at its 
greatest rapidity, rose 4°4°.¢ This elevation of temperature is 
smaller than that which is produced by the absorption of oxygen 
. In vain did I endeavour in these experiments, and in others 
made with a larger piece of charcoal, to perceive some of the water 
which, according to Rouppe and Norden, ought to be formed. 
The gas remaining in the receiver was no Jonger pure oxygen gas, 
but contained, when examined by Volta’s eudiometer, a volume of 
hydrogen gas. Oxygen gas, at the same time, had been absorbed 
by the charcoal, and had driven off more than the half of the 
hydrogen formerly contained in the charcoal. Notwithstanding this, 
the gas in the receiver was diminished 61 volumes. Hence the 
eharcoal had absorbed 61 + 1 = 74 volumes of oxygen, and one 
volume of hydrogen had been driven off. . 
It may be asked now, whether these changes of space are in the - 
* The change of volume was ascertained 24 hours after the charcoal had beea 
putinto it. The receiver in’which the absorption took place was a wide glass 
tube, not much larger than the diameter of the charcoal, the bulk of which was 
about 2°5 cubic centimetres (0°152 cubic inch English). 
+ Rouppeand Norden haye ascribed this elevation of (emperature to the com- 
bination of the oxygen and the hydrogen, and the formation of water, of which,. 
according to them, a perceptible quantity is evolved. They did net perceive that 
this heat was occasioned by the condensation of the oxygen gas, Both reason an& 
experiment are against the possibility of the water being visible, even if it were 
formed ; for in my experiments, as well as in those of these chemists, the charcoal 
had absorbed less than twice its bulk of hydrogen: now that at most could form 
no more water than the five-thousandth part of the weight of the charcoal, But 
experiment informs us that a well dried charcoal, like that which I employed in 
my experiments, can absorb more than the tenth part of its weight of water, and 
yet remain dry, and allow no perceptible portion of that liquid to escape, at the 
temperature of 122° or 140°, Besides, L obtained the same result when L operated 
Upon pieces of charcoal ten or twelve times larger. The heat was indeed some- 
what greater ; but always less than what was generated by the absorption of 
xygen alone by the same piece of charcoal, 
