26 ON Tw METALS, FOUND IN THE POWDER 



dufky olive-green, and finally, by continuing the heat, of a 

 Fufion, kc. re- deep red colour. Part of the powder being yet undiflblved 



peated on the . ,. . . , , * . " . 



undiflblved reft- b . v the marin e acid, was heated as before with alkali ; and, 

 d^. by the alternate a&ion of the alkali and acid, the whole ap- 



Silex, peared capable of folution. At each operation, fome filex 



was taken up by the alkali ; and, as this continued till the me- 

 tallic part was entirely diiTolved, d feems to have been chemi- 

 cally combined with it. 

 The alk. folu- yhe alkaline folution contains the oxide of a volatile metal. 



tion contains an * 



oxide which fe- not }' et noticed, but which I (hall prefently defcribe, and alfo 

 parates byre- a fmall proportion of the other metal. If this folution is kept 

 F ° e ' for fome weeks, the latter metal feparates fpontaneoufly from 



it, in the form of very thin flakes, of a dark colour. 

 The acid fol. The acid folution alfo contains both the metals, but prin- 



ce* m^' but ci P% ^^^ which has bee » mentioned by the French che- 

 principally that mills. The properties of this laft metal, which they have 

 remarked, are thofe of giving a red colour to the triple fait of 

 platina with fal-ammoniac, of not being altered by muriate of 

 tin, and of giving, with pure alkali, a dark brown precipitate. 

 M. Vauquelin alfo adds, that it is precipitated by galls, and 

 by pruffiate of potafh ; but I fliould rather afcribe thefe preci- 

 pitates to fome impurity, and probably to iron. 



As it is necefTary to give fome name to bodies which have 

 not been known before, and moft convenient to indicate by it 

 fome chara&eriflic properly, I fliould incline to call this metal 

 Iridium, from the finking variety of colours which it gives, 

 while diflblving in marine acid. 



In order to obtain the compound of this metal with marine 

 acid in a pure flate, I tried to make it cryftallize. 



By flow evaporation of the folution, only an imperfectly 



cryftallized mafs was produced; but this, being dried on 



blotting-paper, and diffolved in water, afforded, by again eva, 



porating as before, difiind octaedral cryfials. Thefe cryfials 



diffolved in water, gave a deep red coloured folution, inclining 



to orange. With an infufion of galls no precipitate was 



formed, but the colour was inftantly, and almoft intirely, 



taken away. Muriate of tin, carbonate of foda, and pruffiate 



Precip. by alka- of potafh, produced nearly the fame effect. Pure ammonia 



lis and metals, precipitates the oxide ; but (poffibly from adding it in excefs) 



I found it retained a part in folution, acquiring a purple colour. 



The pure fixed alkalis alfo precipitate the greater part of the 



* oxide 



examined by 

 "Vauquelin. 



The name Iri- 

 dium given to 

 the metal exa- 

 mined by Vau- 

 quelin. 



Cryftals of its 



muriate 



diffolved in 

 water. 



