1815.] On Iridium and Osmium. 451 
more readily. The air of the retort was sq impregnated with the 
vapour of this metal that it almost suffocated me. 
The crystals themselves had an odour so strong, that it was im- 
possible to breathe near them without a feeling of pain. 
The osmium which had not been volatilized gave out likewise a 
very striking odour; but I suppose that it owed this property to a 
portion of the air impregnated with oxide, which it had imbibed 
during the cooling. ‘This residue only weighed 0°35 gramme, and 
the quantity of osmium sublimed was far from completing the 
gramme of osmium employed; because a portion of it had passed 
into the water of the receiver, being carried hither by theair. © 
From the result of this operation it appears that oxide of osmium 
is formed only in proportion to the quantity of air in contact with 
it. This is conformable to what we know of the oxidation of the 
other metals. 
Yet 1 am induced to believe that the white oxide formed in this 
case is not entirely owing to the air of the vessel; for it is formed 
and volatilized at a temperature so low, that we can hardly con- 
ceive how the combination should take place. ye 
I am rather disposed to believe that the osmium as it is precipi-« 
tated by zine, still retains a small quantity of oxygen, which when 
assisted by a gentle heat, unites itself to a portion of the metal 
and renders it more volatile, 
The following observation seems to confirm this idea, When the 
osmium is precipitated from its solution by means of zinc, and 
washed several times with water, even acidulated with sulphuric 
acid, it exhales no odour, as long as it is cold; but if it be ex- 
posed to a heat of from 97° to 104°, it exhales the odour during 
some time. 
But the strongest proof is, that osmium which has furnished 
oxide by distillation, does not furnish any more at the same tempe- 
rature, although the same quantity of air be present. 
§ II. Examination of the Oxide of Osmium. 
This oxide is white, transparent, and very brilliant; its taste 
very strong and caustic, has some analogy with that of the volatile 
oils, and particularly with that of oil of cloves, Its odour is equally 
insupportable. It is more fusible than wax ; flexible like it, and 
exceedingly volatile. When placed in contact with animal or 
vegetable bodies, it blackens them, especially if it be moist. It is 
very soluble in water, and the solution becomes blue by nutgalls 
ot many other vegetable substances, 
§ IIL. Action of Oxymuriatic Acid. 
Into a flagon containing about half a litre (30°5 cubic inches) 
into which | had put a gramme of osmium, I passed oxymuriatic 
acid gas, the surplus of which was received in a solution of potash, 
Soon after the osmium came in contact with the gas, it appeared 
282 
