166 On iuo Metals, found in the black Powder 



peculiar smell is immediately perceived. This smell, as I 

 afterwards discovered, arises from the extrication 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 

 pas3 over, a second slow distillation is required, to obtain 

 the oxide perfectly free from it. The solution thus pro- 

 cured 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 iu a phial, the paper lost much of its blue colour, 

 and inclined to giay. 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 

 obialncd in small quantity, but in a more concentrated state, 

 •is, by di.uilling with nitre the original black powder procured 

 from plalir.a. 



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, seniitransparent 

 mass. This, being dissobed in water, forms a solution 

 eimilar to that before described. The oxide, in this concen- 

 trated state, stains the skin of a dark colour, which cannot 

 be eflaced. The most striking test of the oxide of osmium, 

 is an infusion of galls, which presently produces a purple 

 colour, becoming soon after of a deep vivid blue. Bv this 

 means, the presence of this, and of the metal first described, 

 may be observed, when the two are mixed together. The 

 solution of iridium is not apparently altered by being 

 mixed with the oxide of osmium; but, on adding an in- 

 fusion of galls, the red colour of the first is instantly taken 

 away, and soon after the purple and blue colour of the latter 

 appears. The solution of the oxide of osmium with pure 

 ammonia, becomes somewhat yellow, and slightly so with 

 carbonate of soda. It is not affected by pure ntagnesia, nor 

 bv chalk; but with lime a solution is formed of a bright 

 yellow colour. The solution with lime gives with galls a 

 tleep red precipitate, which becomes blue by acids. It 

 produces no effect on a solution of platina or gold; but 

 precipitates lead of a yellowish-brown, mercury of a white, 

 and muriate of tin of a brown colour. 



1 . -The 



