Dr. Henry on the action , &c. 267 
same chemical compounds were formed as by their rapid 
combustion.* 
Facts analogous to these were announced, in the autumn 
of last year, by Professor Dobereiner of Jena, with this ad- 
ditional and striking circumstance, that when platinum in a 
spongy form is introduced into an explosive mixture of oxy- 
gen and hydrogen, the metal, even though its temperature 
had not been previously raised, immediately glows, and 
causes the union of the two gases to take place, sometimes 
silently, at others with detonation. It is remarkable, how- 
ever, that platinum in this form, though so active on mix- 
tures of oxygen and hydrogen, produces no effect, at common 
temperatures, on mixtures of oxygen with those compound 
gases, which were found by Sir Humphry Davy to be so 
readily acted upon by the heated wire.-f Carbonic oxide 
appears, indeed, from the statement of M. M. Dulong and 
Thenard,J to be capable of uniting with oxygen at the tem- 
perature of the atmosphere, by means of the sponge ; but 
though this is in strictness true, yet the combination, in all 
the experiments I have made, has been extremely slow, and 
the due diminution of volume has not been completed till 
several days have elapsed. On mixtures of olefiant gas, of 
carburetted hydrogen, or of cyanogen, with oxygen, the 
sponge does not, by any duration of contact, exert the small- 
est action at common temperatures. 
It was this inefficiency of the platinum sponge on the com- 
pounds of charcoal and hydrogen in mixture with oxygen, 
* Philosophical Transactions, 1817, p. 77. 
f Dobereiner in Ann. de Chim. et dePhys. XXIV— XCVI. 
t Ditto. XXIII. 442. 
