remaimng after /he Solitilon of Plalhia. I fi3 



almost eutirclv, taken away. Muriate of tin, carbonate of 

 soda, and pmssiatc of [jolasli, j^roduced nearly the same 

 effect. Pure ammonia precipitate,-; the oxide; but (possiblv 

 from adding it in excess) I found it retained a part in solu- 

 tion, acquiring a purple colour. The pure fixed alkalis also 

 precipitate the greater part of the oxide, but arc capable 

 of retaining a part in solution, becoming of a vellow 

 colour. ATI the metals which I tried, excepting gold 

 and platina, produced a dark or black precipitate from 

 the niuriated solution, which is at the same time deprived 

 of its colour. The iridium mav be obtained in a pure 

 state, merely by exposing the octaedral crystals to heat, 

 wiiich expels the oxygen and the muriatic acid. It ap- 

 peared of a white colour, and was not capable of being 

 melted by any degree of heat I could apply. I could not 

 combine it with sulphur nor with arsenic. I.ead easily 

 unites with itj but is separated by cupellaticni, leaving the 

 iridium upon the cupel, as a coarse black powder. Copper 

 forms with it a very malleable alloy, which, after cupellation 

 with the addition of lead, left a small proportion of the 

 iridium, but much less than in the former case. Silver may 

 be united with it, and the compound remains perfectly 

 malleable. The iridium was not separated from itbv cupel- 

 lation, but occasioned on the suri'ace a dark or tarnished 

 hue. It appeared not to be pcrfeelly combined with the 

 silver, but merely diffused through the substance of it, in 

 the state of a fine powder. Gold alloyed with iridium is 

 not freed from it by cupellation, nor by quartation with 

 silver. The compound was nialleable; and did not differ 

 much in colour from pure gold, though the proportion of 

 alloy was very considerable. If tlie gold or silver is dis- 

 solved, the iridium is left, in the form of a black powder. 



Theyellowalkalinesolution, which I have already mention- 

 ed as containing a metallic oxide, distinct from the former, 

 i'S considered bv M. Vauquclin as a solution of the oxide of 

 chrome in alkali ; but I could not, bv any test, discover the pre-: 

 senceof chrome. After the superfluous alkali had been neu- 

 tralized by an acid, it produced a pale or bp.tT-coloured pre-r 

 cipitate with a solution of lead, and not the bright yellow 

 which is given bv chrome. But, as we are indebted to the 

 above distinguitihed chemist, among many other important 

 discoveries, for our knowledge of the existence of chrome, it 

 is not improbable that some kinds of platina may contain 

 that substance, besides the other bodies usually mixed with 

 it.i When the alkaline i.olution is first formed, by adding 

 «ater to the dry alkaline m.Tss in the crucible^ a pungent and 



r.. 'A peculiar 



