from the Ores of Platinum, ~ 173 
the above, but with this difference, that the acids ought to be as 
concentrated as possible. 1 employ for this purpose nitric acid, 
at 40° (1.387 sp. gr.) and muriatic acid, at 234° (1.195). The 
retort is placed on a sand-bath, with a tubulated receiver adapted 
to its neck, and it is heated moderately.’ A brisk effervescence 
sdon arises, owing to the disengagement of much nitrous vapour, 
and a little chlorine. The action of the heat must be so modi- 
fied as to produce the most beneficial effect on the solution, with- 
out volatilizing the acid. Finally, when the effervescence ceases, 
the fire is to be augmented till the liquid boils, and till no more 
orange nitrous fumes are disengaged. 
~ When the action of the acid is quite exhausted, we decant the 
liquid into a matrass, and pour on the portion of the ore not at- 
tacked the same nitro-muriatic acid, equal in quantity to ‘the 
first. 
The mixture is to be heated anew, observing the same precau- 
tions as for the preceding solution. Finally, we treat the ore five 
times in succession with the compound acid. By this process six 
parts of this acid are sufficient to dissolve the whole platinum, 
palladium, and rhodium contained in the ore. 
8. After the last digestion, which yields only a slightly reddish- 
coloured solution, there remains a residuum, under the form of 
a brilliant blackish powder, which consists of an alloy of iridium 
and osmium. One part of this is a fine powder (see Note to pa~ 
ragraph 1), and the other forms brilliant spangles. We shall 
return in the sequel to the residuum; let us employ ourselves at 
present on the solution. 
9. We have said that all the platinum, rhodium, and palladium 
were dissolved ; but the acid also dissolves. a little iridium and 
osmium, as well as the iron alloyed with the platinum grains. 
During the action of the acid on the ore, at the same time that 
the nitrous gas and chlorine ace evolved, there is volatilized a 
little water and muriatic acid, which carry over with them a no 
table quantity of oxide of osmium, which is condensed in the 
receiver. 
10. All the successive solutions of the ore of platinum are 
united and introduced into a retort of proper capacity, to which 
the receiver containing the former condensed vapours is attached. 
The retort is now heated on a sand-bath, till its contents acquire 
the consistence of svrup. By this means we drive off all the ex- 
cess of the acid, which carries along with it into the receiver the 
whole oxide of osmium which that solution contained. 
11. The product of the last distillation being saturated with 
lime, we distil over to one-half the volume. ‘The product of this 
aew distillation has an extremely penetrating odour, on account 
of 
