from the Ores of Platinum. 177 
diately there is formed, in the liquid, a precipitate in the shape 
of small needles, delicate and shining, possessing a beautiful pale 
rose-colour.. This crystalline precipitate is an ammonio-sub- 
protomuriate of palladium. Since this salt is insoluble, there can 
remain none of it in the liquid. It may be separated by the 
filter, and washed with very cold water. By heating this salt to 
redness in a crucible, the palladium remains pure. It may be 
afterwards melted in a cavity of ignited charcoal, on which a 
stream of oxygen gas is made to play. 
20. The liquid freed from the salt of palladium, possesses a 
fine currant-red colour, derived from the ammonio-muriate of 
rhodium, which it holds in solution, and which is very soluble. 
It contains, moreover, a little muriate of iron, and occasionally 
a little muriate of copper, when this metal has not been entirely 
dissolved by the first portion of nitro-muriatic acid, which was 
made to act on the ore, as has been stated above. There are 
two modes of treating this salt, to obtain pure rhodium. The 
first consists in evaporating this liquid, at a gentle heat, to dry- 
ness; and boiling the residuum several times along with abso- 
lute alcohol. The spirit dissolves all the muriate of iron and 
copper, with the excess of sal-ammoniac, and does not affect the 
ammonio-muriate of rhodium, which remains in the form of a 
saline powder of a fine carmine-red colour. By calcining this 
salt to redness in a crucible, we decompose it, aud the rhodium 
remains pure and perfectly metallic. ‘The second means of ob- 
taining the rhodium from the above liquid, consists in plunging 
into it plates of iron. The rhodium and the copper are precipi- 
tated, carrying down with them a little iron. When every thing 
is fallen down, the liquor is decanted, the precipitate is washed, 
and boiled with an excess of strong muriatic acid, which dis- 
solves all the iron. The liquid is now poured off, the residuum 
is washed with a sufficient quantity of water, and is next boiled 
several times with concentrated nitrie acid, which dissolves all 
the copper. The rhodium being completely insoluble in each of 
‘these acids separately, remains under the form of shining pelli- 
cles, which must be washed and dried. Rhodium being the 
most infusible of metals, cannot be melted but in small pieces, 
by the aid of a flame fed with oxygen gas, or by the compound 
flame of hydrogen and oxygen. 
21. Let us return to the black powder separated from the pla~ 
tinum ore, by treating it with nitro-muriatic acid. We have said 
that this black powder was an alloy of osmium and iridium. It 
is scarcely affected by any nitro-muriatic acid. It requires, in- 
deed, an enormous .quantity of this acid to dissolve a minute 
particle of it, The only means of attacking this alloy, is to cal- 
Vol. 59. No, 287. March 1822. Z cine 
