8 MITSCHERLICH ON CHEMICAL REACTIONS 
perature, we pour some mercury by means of a funnel the point 
of which touches the bottom of the tube, and we then heat it, it 
does not yield the least bubble of air, even if mercury has been 
used which has been shaken with air and water, and it has been 
left to dry simply in the open air; thus the gaseous bubbles 
which the mercury yielded in the first experiment must have 
come from the air and water condensed upon the sides of the 
tube; but this quantity of air and water condensed in the first 
case is so very small, that its presence can only be shown by the 
experiment which we have just related. 
It would be impossible to prove the condensation of any gas 
on the surface of laminz of platinum, supposing even that it 
was as considerable as that of carbonic acid on the surface of 
charcoal. : 
A mixture of alcohol and oxygen behave, in presence of pla- 
tinum, precisely in the same manner as a mixture of hydrogen 
and oxygen. The oxygen is without action upon the alcohol, 
weak or concentrated; the platinum black induces their com- 
bination. Other bodies are similarly cireumstanced. It has been 
thought that, in order to effect this reaction, it was necessary to 
have recourse to the employment of ferments, until M. Duflos 
had proved that shavings of wood steeped in acetic acid acted 
in an analogous manner to platinum black. It might have been 
thought that the acetic acid which was employed had deposited 
ferment upon the shavings; but the ferment would soon have 
been decomposed by the oxygen of the air; and M. Duflos has 
proved that alcohol might be converted during entire months 
into acetic acid with shavings alone. 
When acetic acid is prepared by exposing beer or fermented 
liquors of this kind to the action of the air, they become thick 
and deposit matters of organic nature. These spongy matters, 
acting in the manner of platinum black, are able to condense 
oxygen, and then determine the combination of the bodies. 
We can better account for the action of bodies which act by 
contact, when we study the cases in which they induce decom- 
positions. If we pass some ammoniacal gas over incandescent 
copper or iron shavings, it is entirely decomposed into nitrogen 
gas and hydrogen gas; whereas, on passing it over platinum 
turnings or fragments of glass, only an extremely small quan- 
tity on the contrary is decomposed. 
The decomposition of the binoxide of hydrogen is of the great- 
