1815,] On Iridium and Osmium. 453 
which protects it from the action of these menstrunms.... This sub- 
stance can only be iridium, since it is it which resists solution most 
obstinately. 
The combination of the oxide of osmium with the alkalies, dis- 
solved in water, has a yellow colour. ) Ny 
Though the oxide of osmium does not present acid characters, 
yet it appears that it combines with the alkalies, and that it is in 
some measure fixed by this combination. In fact, if it were not 
so, this metal would escape entirely when the black powder is 
treated in crucibles with potash or nitre at a red heat. 
What. gives a certain degree of force to this opinion is, that the 
addition of any alkali whatever to the aqueous solution of osmium 
very much diminishes the odour, which again becomes powerful, 
when the alkali is neutralized by an acid. 
The small quantity of osmium which [have been hitherto able 
to procure, and its great oxidability, have not enabled me to examine 
if it would unite with sulphur, phosphorus, and the other metals ; 
but these combinations never can be any thing else than mere 
objects of curiosity. 4 
The characteristic properties of osmium are to oxidate at a low 
heat, and to form an oxide exceedingly volatile, odorous, and 
fusible ; crystallizable, soluble in water; the solution of which 
becomes blue by the infusion of nutgalls, and by the immersion of 
a plate of zinc: finally, the property-of forming yellow combina- 
tions with the alkalies. 
ArticLE XII. 
Proceedings of Philosophical Societies. 
ROYAL SOCIETY. 
_ On the 9th of November the Society met for the first time after 
the long vacation. A paper by Sir H. Davy on the fire-damp in 
coal-mines was read. The author had been invited by Dr. Grey to 
examine the subject, in order to discover, if possible, some method 
of preventing those explosions which of late years have proved so 
fatal to the lives of the colliers, He accordingly visited several of 
the mines, and analyzed the pure gas collected from a blower. He 
States, as Mr. Longmire had done before him (Annals of Philo- 
Sophy, vi. 172), that this gas is extricated from the crevices of the 
coals; and he found that when a large piece of coal was broken to 
pieces under water, inflammable gas was given out. The result of 
lis analysis of the gas was precisely the same with the previous 
result obtained by Dr. Henry (Nich. Jour, xix. 149), that it was 
pure carbureted hydrogen gas. It required twice its bulk of oxygen 
gas to consume it, and nearly its own bulk of carbonic acid gas, 
4 
