Royal Society of London. 273 



This led him to the discovery of the new metal which he 

 named rhodium, and also to the discovery which forms the 

 principal subject ot this paper. He mentions also having 

 found blended with plat.na the ore of another metal, which 

 has hitherto passed imubserved trom its great resen)blance 

 to the grains of that metal. These grains he considers as 

 the ore of iridium, the ne.v metal discovered by Mr. Ten- 

 nant. They are insoluble in nitro-muriatic acid, are harder 

 than platiua, brittle under the hammer, and break with a 

 laminated fracture. Mr. Tennaiit has undertaken the ana- 

 lysis of a portion of this ore. 



The author mentions having separated from the ore of 

 platina, by a current of water, some very minute red cry- 

 stals, the quantity of which was too small to admit of ana- 

 lysis ; but from such an examination as he could give them 

 he concludes them to be hyacinths. 



Havino; separated these and other impui-ities from the 

 ore ofpfatina, as far as practicable by mechanical means, 

 dissolved the ore, and obtained, in the form of a yellow 

 triple salt, all the platina that could be precipitated by sal- 

 ammoniac, clean bars of iron were used to separate the re- 

 maining plaiina. This precipitate, consisting of various 

 metals, was subjected again to exactly ihe same treatment, 

 when the precipitate obtained by sal-anunoniac was found 

 to be not of so pale a yellow as before : bars of iron were 

 also again used to precipitate what remained suspended. 

 A repetition of the same process on this second precipitate 

 led to the discovery of palladium ; for Dr. Wollaston found 

 that a portion of it resisted the action of the nitro-muriatic 

 acid, though this powder had been twice completely dis- 

 solved before. The solution was very dark in colour, yielded 

 by sal-annnoniac only a small quantity of precipitate, and, 

 instead of becoming pale by the precipitation of the platina, 

 retained the dark colour which it had acquired from the 

 other metals held in solution. The second metallic preci- 

 pitate, therefore, became the subject of investigation. Lead, 

 iron, and copper, were detected in it by nnariatic acid. Di- 

 lute nitrous acid separated a further portion of copper, form- 

 ing, as usual, a blue solution ; but when a stronger acid 

 was used for the ]5urpose of scpara; ing the remaining cop- 

 per, the dark brown colour of the solution gave evidence 

 that some other metal had been dissolved. A small portion 

 of the solution was put on a suiface of platina ; and on ap- 

 plying a clean plaie-of copper a black precipitate was ob- 

 tained, solu!)le in nitric acid, and consequently neither gold 

 nor platiua. The solution in that acid was red, tbereiore 

 the metal was neither rilver nor mercury; and having been 



Vol. 22. No. 87. Ju;i!ist 1805. S precipitated 



