502 | M. Martius on the Platinum Metals. 
' The action of strong potash on butyryle is very energetic ; 
butyrate of potash is formed as well as a substance of a pleasant 
odour, which has the composition of the ketone of butyric acid, 
but in properties appears to be quite different. 
Martius* has published an investigation on the cyanides of the 
metals associated with platinum. In their preparation he used 
the residues obtained from the manufacture of Russian platinum. 
The method of separating the metals which he adopted is a com- 
bination of several methods, and presents some interesting points. 
The residues were finely powdered, and the larger grains of 
osmium-iridium separated by decantation. The residue having 
been dried and heated, was fused with a mixture of lead and oxide 
of lead, by which all the silicates and other similar impurities 
passed into the slag, and a lead regulus was obtained containing © 
all the platinum metals. When this was treated with diluted 
nitric acid, a residue was left consisting principally of iridium and 
osmium-iridium. The latter was separated by decantation. To 
bring it into a state of fine powder, which could not be effected 
in the ordinary way on account of its hardness, it was melted 
with zinc in a carbon crucible, by which it was dissolved ; when 
this mass was afterwards heated! in a wind furnace, the zinc was 
expelled and the mineral left in a state of fine powder. 
The osmium-iridium was then heated in a current of oxygen ; 
some osmic acid was formed, which volatilized, and was collected 
in a well-cooled receiver. The residue and the iridium were 
then mixed with an equal weight of common salt, and heated in 
a current of chlorine; the mass was dissolved in water, and the 
solution which contained the double chlorides was boiled with 
aqua regia, by which osmium was removed as osmic acid, and 
was received in a solution of ammonia. The residual solution 
was then mixed with sal-ammoniac, which precipitated everything, 
excepting a little rhodium, as ammonium double salt. The pre- 
cipitate consisting principally of iridium, but containing also some 
platinum and ruthenium, was fused with cyanide of potassium 
to convert it into eyanides; this was boiled with hydrochloric 
acid to decompose excess of cyanide of potassium, and then sul- 
phate of copper added, which gave a red precipitate of the cop- 
per salt. 
By digesting this precipitate with baryta water, oxide of copper 
was formed and the barium double cyanides. They were easily 
separated by crystallization, the platimocyanide of barium being 
more insoluble than the iridiocyanide of barium. The small 
quantity of ruthenium was contained in the mother-liquor of this 
latter salt. 
* Liebig’s Annalen, March 1861. 
