1815.] R»yal Institute. 4CI 



even wUen very weak, and then acts upon gelatine like astringent 

 bodies, and forms oxalic acid when acted on by nitric acid. It 

 possesses, besides, some other characters, which seem to raise it to 

 the rank of a peculiar vegetable principle. The colouring matter of 

 alcanette dissolves in ether, alcohol, and expressed oils. When 

 treated with nitric acid, it gives oxalic acid and bitter principle. 

 Alkalies and water make it undergo various changes of colour. 

 These united properties, in the opinion of M. Pelletier, entitle it 

 likewise to be considered as a peculiar vegetable principle. 



VVe have seen formerly that crude platina, as extracted from the 

 mine, contains several foreign substances, and among othei-s, four 

 peculiar metals, which have been lately described. Last year we 

 described the methods employed byM. Vauquelin to separate /)a//«- 

 dhnn and rhodium (two of these metals form a solution of platinum 

 in nitro-muriatic acid) ; and to obtain them in a state of purity. We 

 mentioned, likewise, that M. Laugier having perceived that this 

 .solution contains a notable quantity of a third metal, remarkable f^r 

 its volatility, on which account it received tiic name of Qsmmm, had 

 pointed out a method of collecting it. 



A black powder, which does not dissolve in nitro-muriatic acid, 

 remained to be examined. It fori.M tlic residuum after the solution 

 of crude platinum. It is composed chiefly of osmium, and of a 

 fourth metal, to which, on account of the various and lively colours 

 of its solution, the name of iridium has been given. 



These two metals are united in that powder with chromium, iron, 

 titanium, silica, and even with a little alumina. The difficulty was 

 to separate them completely from this mixture, and to obtain them 

 in a state of purity. 



Vauquelin has succeeded in this, but by laborious and compli- 

 cated processes. 



Simple washing divides this powder into two parts ; one, finer 

 and more brilliant, contains more iridium and osmium, and scarcely 

 any chromium ; the other, browner and coarser, contains less of 

 ihe first two metals and more of tiie others. As tliis last portion is 

 the most difficult to analyze, we shall confine ourselves to it. 



M. Vauquelin tiiturates it in the first place with twice its weight 

 of nitrate of potash. The oxygen of the acid oxidates the iridium 

 and osmium, which combine with the disengaged potash. The 

 application of hcjit disengages a great part of the acid and the 

 osmium, which are received in lime-water. The residue, diluted 

 and saturated with nitric acid, gives a precipitate of iridium, tita- 

 nium, iron, alumina, and a little oxide of chromium, and there 

 remains a liquid composed of potash united to chroniic acid and to 

 osmium. Tiiis last metal is separated by adding nitric acid and 

 distilling, receiving the osmium in a flask surrounded by ice. A 

 little muriatic acid is poured into the water containing the osmium. 

 A plate of zinc is then introduced, which prccipit:Uts the osmium, 

 'i'o obtait) it quite pure it is wailicd with vvatvr aciJulaied uldi a 

 little sulphuric acid. 



