AZ” On Iridium and Osmium. (Dec. 
§ Il. Analytic Process. 
What renders the analysis of the black powder from crude pla- 
tinnm’ so complicated and diflicult, is the great number of substances 
which it contains. That we may be able to follow the series of 
operations to which it is necessary to subject it, I think it necessary 
to point out these substances. 
The black powder contains chromium, osmium, iridium, tita- 
nium, iron, sand, and even a little alumina. ? 
50 grammes of the black powder well pulverized being mixed 
with 100 grammes of nitre, I introduced the mixture into a porce~ 
lain retort, to which I adapt a tube plunging into lime-water. The 
retort is gradually heated, and the heat continued till gas ceases to 
be disengaged. 
Effects. 
The first effect is the disengagement of a gas, which is probably 
a mixture of oxygen and azote; the second, a light yellow preci~ 
pitate in the lime-water through which the gas passes ; the third, the 
formation of a great number of small white crystals in needles in 
the tube which conducts the gas to the lime-water; the fourth, the 
disappearance of the precipitate formed in the lime-water, and of 
the yellow colour of that liquid; the fifth, the disappearance of the 
crystals contained in the tube. From this period, to that when gas 
ceases to come over, no further change takes place. 
§ UI. Examination of the Products of the preceding Operation, 
and Explanation of the Phenomena. 
1. The lime-water through which the gas had passed was become 
acid, It gave out a strong smell of osmium: accordingly nutgalls 
gaye it immediately an intense blue colour. This proves that the 
crystals formed in the tube at the commencement of the operation 
were oxide of osinium, and that these crystals were carried to the 
lime-water by the hot gas which passed over them continually. 
2, The yellow colour whieh the lime-water assumed at first was 
owing to its combination with osmium, which the nitrous acid that 
afterwards came over destroyed. m 
3. The water which I introduced into the retort to soften the 
residue assumed a very deep reddish-brown colour. This liquid had 
not the odour of osmium, as that has which we obtain from the 
residuum of crude platinum melted with potash. This might lead 
to the suspicion that the osmium, had been entirely volatilized, 
which, however, is not the case, as we shall see hereafter. ~ 
4, When the excess of alkali contained in this liquid is saturated 
with nitric acid, a green flocky precipitate is formed, composed of 
iridium, titanium, iron, alumina, and sometimes of a little oxide of 
chromium. The liquid then assumes the yellow colour of chromate 
of potash, and gives out a strong smell of osmium, showing that 
this metal had been in combination with the alkali. 
1 ; 
—et—“‘CSC!COU™™C 
