44 6 Mr. Tennant on two Metals, found in the Powder 
some kinds of platina may contain that substance, besides the 
other bodies usually mixed with it. When the alkaline solution 
Is first formed, by adding water to the dry alkaline mass in the 
crucible, a pungent and peculiar smell is immediately perceived. 
This smell, as I afterwards discovered, arises from the extrica- 
tion of a very volatile metallic oxide ; and, as this smell is one 
of its most distinguishing characters, I should on that account 
incline to call the metal Osmium. 
This oxide may be expelled from the alkali by any acid, and 
obtained in solution with water by distillation. The sulphuric 
acid, being the least volatile, is the most proper for this purpose ; 
but as, even of this acid, a little is liable to pass over, a second 
slow distillation is required, to obtain the oxide perfectly free 
from it. The solution thus procured is without colour, has 
a sweetish taste, and the strong smell before mentioned. Paper 
stained blue with violets, was not changed by it to red ; but, by 
being exposed to the vapour of it in a phial, the paper lost much 
of its blue colour, and inclined to gray. As a certain quantity of 
this oxide is extricated during the solution of the iridium in 
marine acid, that part may also be obtained by distillation. 
Another mode by which the oxide of osmium may be obtained 
in small quantity, but in a more concentrated state, is, by dis- 
tilling with nitre the original black powder procured from 
platina. 
With a degree of heat hardly red, there sublimes into the 
neck of the retort, a fluid apparently oily, but which, on cooling, 
concretes into a solid, colourless, semitransparent mass. This, 
being dissolved in water, forms a solution similar to that before 
described. The oxide, in this concentrated state, stains the skin 
of a dark colour, which cannot be effaced. The most striking 
