Iridium alloys black

Uses.—Rhodium is used, both alone but generally alloyed with platinum, in the construction of scientific apparatus such as crucibles. A rhodium crucible is, for all practical purposes, as resistant as one of iridium, and is both cheaper and lighter.7 It has also found application in the manufacture of thermo-electric couples.8 Rhodium black has been used for producing a black colour in the decoration of poree lain.9... 

When platinum is heated in a luminous coal-gas flame a black layer is formed. If the carbon is now burnt off in air the metal is left in a rough and brittle condition, but without having undergone any loss in weight. The action is considerably enhanced by the presence of alloyed rhodium or iron, whilst iridium has a less marked effect.8... 

The post-mortem investigation discovered a metallic sphere, 1.52 mm in diameter (about the size of a pin s head), just below the surface of the skin at the site of the puncture mark. The sphere, made of an alloy of platinum (90%) and iridium (10%), had two holes in it, of diameter 0.35 mm, that extended across the entire sphere. This would allow about 0.28mm of a substance to be stored. The pellet was checked by the Government Chemical Defense Establishment at Porton Down but no traces of any substance could be found. Despite this, owing to the symptomatology and the very high toxicity required for so small a dose, the Coroner was satisfied that the cause of the poisoning was ricin. The pellet found in Mr. Markov was placed in the Black Museum at New Scotland Yard but has since been removed to serve as a piece... 

The notorious black powder was, evidently, a natural alloy of osmium with iridium, the so-called osmiridium. Iridium is known to be chemically stable and in the compact form does not dissolve even in aqua regia. On the contrary, osmium is readily soluble in aqua regia in general among platinum metals osmium has the most atypical chemical... 

---