ss 



txpellable from 

 the alkali by an 



acid 5 



or obtained by 

 diftilfing the 



black powder 

 with nitre. 



Procefs de- 

 scribed* 



Mofl: flriking 

 character of fo- 

 lution of ofmi- 



Habitudes with 

 various bodies ; 



ON TWO METALS, FOUND IN THE POWDER 



■wards discovered, arifes from the extrication of a very volatile 

 metallic oxide; and, as this fmell is one of its mod diftin- 

 guifliing characters, I fhould on that account incline to call 

 the metal Ofmium. 



This oxide may be expelled from the alkali by any acid, and 

 obtained in folution with water by diftillation. The fulphuric 

 acid, being the leaft volatile, is the moft proper for this pur- 

 pofe ; but as, even of this acid, a little is liable to pafs over, 

 a fecond flow diftillation is required, to obtain the oxide per- 

 fectly free from it. The folution thus procuied is without 

 colour, has a fweetifli tafte, and the ftrong fmell before men- 

 tioned. Paper flained blue with violets, was not changed 

 by it to red ; but, by being expofed to the vapour of it in a 

 phial, the paper loft much of its blue colour, and inclined to 

 gray. As a certain quantity of this oxide is extricated during 

 the folution of the iridium in marine acid, that part may alio- 

 be obtained by diftillation. 



Another mode by which the oxide of ofmium may be ob- 

 tained in fmall quantity, but in a more concentrated ftate, is, 

 by diftilling with nitre the original black powder procured 

 from platina. 



With a degree of heat hardly red, there fublimes into the 

 neck of the retort, a fluid apparently oily, but which, on 

 cooling, concretes into a folid, colourlefs, femitranfparent 

 mafs. This, being diffolved in water, forms a folution fimilar 

 to that before defcribed. The oxide, in this concentrated 

 ftate, ftains the Ikin of a dark colour, which cannot be effaced. 

 The moft ftriking teft of the oxide of ofmium, is an infufion 

 of galls, which prefently produces a purple colour, becoming 

 foon after of a deep vivid blue. By this means, the pretence 

 of this, and of the metal firft defcribed, may be obferved, 

 when the two are mixed together. The folution of iridium 

 is not apparently altered by being mixed with the oxide of 

 ofmium ; but, on adding an infufion of galls, the red colour 

 of the firft is inftantly taken away, and foon after the purple 

 and blue colour of the latter appears. The folution of the 

 oxide of ofmium with pure ammonia, becomes fomewhat 

 yellow, and flightly fo with carbonate of foda. It is not 

 affected by pure magnefia, nor by chalk ; but with lime a 

 folution is formed, of a bright yellow colour. The folution 

 with lime gives with galls a deep red precipitate, which 



becomes 



