1815,] On Iridium and Osmium. 439 
salt, so deep as to be easily mistaken for charcoal in powder, On 
examining this salt, I found it a muriate of iridium-and-potash, of 
which I shall speak in another article. 
_7. If the solution which has thus yielded crystals be diluted with 
four or five times its bulk of water, if the iron be precipitated by 
ammonia, and the precipitate well washed, we find in it no trace of 
iridium. Yet the liquid is not coloured, nor does it become 
coloured by concentration, and the sa!-ammoniac which it yields is 
white. One would suppose, then, that it contained nothing 
metallic. But if oxymuriatic acid be mixed with this liquid con- 
centrated, it immediately assumes a red colour; and if we drive off 
the sal-ammoniac which it furnishes, it leaves a black powder, which 
is metallic iridium. 
_ The second muriatic solution of the black powder from platinum, 
or that which has a greenish-blue colour, presents in general the 
same properties as the preceding; but all the qualities indicating 
iron are less distinct in it, while those indicating iridium are 
more so. 
Thus the precipitate formed in it by alkalies is less abundant, and 
of a colour more inclining to blue. The diminution of colour pro- 
duced in it by sulphate of iron and sulphureted hydrogen is much 
more complete. ‘The red colour which it acquires by heat and oxy- 
muriatic acid is much more pure. 
The third solution, which is of a pure blue, exhibits still more 
distinctly the phenomena depending on the presence of iridium, 
while those depending on iron become always feebler. 
If we pour some of that last solution into a solution of potash, 
taking care to have an excess of alkali, a light yellow precipitate is 
formed, and the liquid assumes a pure blue colour. The precipitate 
is occasioned by the oxide of iron, and the blue colour of the alkaline 
solution by the oxide of iridium. Hence it follows that if the solu- 
tion of iridium was pure, it would not be precipitated by an excess 
of potash. This will be confirmed hereafter, 
§ IX. Examination of the Precipitate B. 
A portion of this matter put into muriatic acid while yet moist 
was speedily dissolved. The solution, which had a very intense 
bottle-green colour, was put to the following trials. 
1, It was precipitated in green flocks by the alkalies. 
2. Sulphureted hydrogen immediately deprived it of its green 
colour, and gave it a slight fawn colour. Some drops of alkali let 
fall into the liquid thus discoloured throw down green flocks, as if 
no sulphureted hydrogen had been used. 
3. Infusion of galls destroys the green colour, and produces a 
brown, 
4. The prussiate of potash, without occasioning a precipitate, 
renders the green colour more intense, giving it a slight shade of 
blue, which indicates the presence of iron. 
5. When the solution of this substance is heated, it exhales an 
