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tion of oxygen by the gallic or pyrogallic acid under the 
influence of alkalies, a certain quantity of a permanent and 
combustible gas is produced, viz. — oxide of carbon. 
It was during a series of experiments which I had under- 
taken to verify a most interesting fact, published by M. 
Boussingault, viz., the production of oxide of carbon during 
vegetation under water, or the decomposition of carbonic acid 
under the influence of solar rays (see Comptcs Hendus. vol. 
63, p. 862, 1862), that I discovered that the oxide of carbon 
which M. Boussingault had obtained in his analysis of the 
gas mixture produced during vegetation, was not due, as he 
thinks, to the reduction of carbonic acid into oxide of carbon ; 
but that this gas was a product of oxidation, or the result of 
the action of oxygen on the pyrogallic acid that he used for 
analysing his gas mixtures. 
The following details of my experiments will, I trust, 
clearly prove this curious production of oxide of carbon : — 
1 . If over a mercury trough 1 00 cubic centimetres of oxygen 
are introduced under a bell jar together with pyrogallic acid 
and potash, although the greatest portion of the oxygen is 
rapidly absorbed, still whatever number of hours the sub- 
stances are left in contact, there will always remain a certain 
residue incapable of further absorption, and on examining 
this residue, it will be found to burn with a blue flame, and 
to be converted thereby into carbonic acid, which compound 
is easily characterised. 
2. If two litres of oxygen, free from any trace of carbonic 
acid, are made to pass through a solution of pyrogallate of 
potash placed in Liebig’s bulb apparatus, and from thence 
over carefully prepared oxide of copper, heated to a dull red 
heat, carbonic acid will be found to issue from the apparatus, 
and can be collected and weighed. 
3. If an unabsorbed portion of gas remaining in the receiver 
(Experiment, No. 1), be brought into contact with a solution 
of protochloride of copper, dissolved in hydrochloric acid or 
