448 On Iridium and Osmium. {Due. 
form of a black powder; but it was not pure iridium. It was 
mixed with a certain quantity of muriate of potash, as was obvious 
from the taste. 
This residue, being repeatedly washed with hot water, and dried, 
was reduced to 37 parts. 
If we were certain that no muriate of potash was dissipated 
during the calcination, we should have from the preceding expe- 
riment two elements of the salt; namely, the metal and the 
muriate of potash. This metal would be to the muriate of potash 
as 37 : 13, or as 3: 1.: It would be only necessary after this to 
know the quantity of water and muriatic acid which were disen- 
gaged during the process to know that of the oxygen. 
§ 1H. Sulphuration of Iridium. 
A hundred parts of the ammoniaco-muriate of iridium, mixed 
with as much sulphur, and gradually heated to redness. in a re- 
tort, furnished 60 parts of a black agglutinated powder, whieh 
burnt, when heated, like the metallic sulphurets. 
We have seen above that 100 of this salt furnish from 42 to 45 
of metal. They would then have absorbed 15 of sulphur, sup- 
posing the last result the most aceurate. But it is evident, that if 
45 absorb 15, 100 will absorb 33:3, ; ; 
Mr. Tennant says, that he could not unite sulphur to iridium, 
Probably because he attempted the direct combination; but the 
ease is different when we employ its triple ammoniacal salt. 
§ I. Alioys of Iridium with some other Metals. 
Lead and Sridium.—Eight parts of lead and one part of iridium, 
heated on charcoal by means of the blow pipe, united as soon as 
the lead became white hot. 
The ductility of the lead was not destroyed by this quantity of 
iridium ; but its hardness and whiteness had heen very sensibly 
increased. This alloy is attacked by nitric acid, which dissolves 
the lead, and leaves the iridium in the state of a black powder, 
Copper and Iridium.— Four parts ef copper and one of, iridium 
united as soon as the copper was white hot. ‘The alloy is ductile ; 
but much harder than pure copper. The .colour is pale red, ap- 
pearing white under the file. It was acted on by nitric acid in the 
same way as the alloy of iridium and lead. ‘The copper dissolved, 
and the iridium remained ; yet the acid appeared to have dissolved 
some particles of it, as the colour of the solution, instead of being 
blue, was green. 
Tin and Lridium.—Four parts of tia and one of iridium give a 
dull white alloy, easily erystallized, hard, but malleable. The 
iridium does not combine with the tin till the latter is white hot. 
Silver and Jridium.—Two parts of fine silver and one of iridium, 
heated like the others before the blow pipe, did not unite com- 
pletely, probably because there was too great a quantity of iridium. 
I endeavoured to bring about the consbination, by means of the 
’ 
