1815,] On Iridium and Osmium. A3Z 
black matter, and appears to act no further, it is decanted off, and 
the residue is washed with water, which is added to the first solu- 
The liquid, though diluted with a great quantity of water, has a 
green colour, so deep that it intercepts the passage of light, unless 
it be in a very thin layer. ) 
If, notwithstanding the precaution indicated above, this solution, 
still gives out the smell of osmium, it must be put into a retort, and 
subjected to distillation. The osmium will be obtained in the water 
that comes over acidulated with muriatic acid. From this it is to be 
precipitated by a plate of zinc in the manner described above. While 
this liquid is kept boiling, in order to disengage its osmium, it de- 
posites a great quantity of matter of a bottle-green colour, and the 
liquid assumes a very deep reddish-brown colour. 
This green matter is separated by the filter, and washed with a 
great deal of hot water. I shall denote it by the letter B. 
Black powder treated only once with two parts of nitre does not 
dissolve entirely in muriatic acid, however great a quantity of it we 
employ. There remains always at least + under the form of a bluish 
powder, containing white brittle metallic grains. This metallic 
residue, indeed, may be dissolved by boiling it for a long time in 
very strong nitromuriatic acid; but the process is long and expen- 
sive. The labour is greatly abbreviated by treating it with its own 
weight of nitre and heat. Then the matter oxidizing by means of 
the salt combines with the potash set at liberty, and then dissolves 
in muriatic acid, communicating to it a fine blue colour. 
If there still remain some portions of matter which refuse to 
dissolve in muriatic acid, we must treat them again with nitre ; and 
this process must be repeated till the whole be dissolved. 
§ VIII. Examination and Properties of the above Muriatic. So- 
lutions. 
When the black powder from platinum is thus treated alternately 
with nitre and muriatic acid, after having separated the chromium 
and osmium, we observe that the first muriatic solution is of a 
yellowish-green colour ; the second, of a bluish-green ; the third, 
of a greenish-blue; and all the subsequent ones blue. We ob- 
serve, likewise, that the last mixtures of the powder with nitre 
communicate to the water employed to wash it a colour equally 
blue. 
Oo examining the different solutions, 1 found that the first con- 
tained a good deal of iron and titanium, and but little iridium, In 
the second there was less iron and titanium, and more iridium. In 
the third, still less iron, and very little titanium ; but some traces 
of iron were always to be observed, even to the very last solution. 
These effects are easily conceived, when we reflect that the first 
solution ought to contain all the iron coming from the chromate, and 
all the titanium the union of which with that metal has been de- 
