Rhodium alloys soluble

Alloys containing less than 5 per cent, of rhodium are soluble in aqua regia. An alloy containing 30 per cent, of rhodium is insoluble in aqua regia, and is more readily fused than rhodium itself.3... 

Metallic rhodium or an alloy with Au is almost insoluble, unless very finely divided, in HNO3/HCI. Alloyed with Cu, Pt, Pb or Bi, rhodium is soluble in HNO3. Freshly precipitated Ir may be dissolved in aqua regia. Compact or ignited Ir is insoluble in all aqueous acids. A Pt-Ir alloy containing 25 to 30% Ir is not attacked by aqua regia. 

Rhodium was discovered by Wollaston (England) in 1803, Compact Rh is almost insoluble in all acids at 100cC, including aqua regia. Hot concentrated HiSCLi will slowly dissolve the finely divided metal. When alloyed with 90% or more of Pt, it is soluble in aqua regia. The metal is attacked by fused bisulfates. Rh is soluble in molten Pb, This is the basis of the classic separation of Rh and Ir. 

It alloys with gold, an alloy, which probably contains a real compound, being obtained with 1 per cent, of rhodium, and which is entirely soluble in aqua regia. A 10 per cent, mixture yields free rhodium, on cooling, in the form of feathery crystals, whilst if still more rhodium is present, it separates as the amorphous metal.1... 

FP-4 (zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, indium, tin, antimony)—are only slightly soluble (<1 wt %) in the process alloy, thus will partition between both product streams. The process, as presented, offers no method of FP-4 removal and possibly an unwanted increase in these products would occur if the fuel were to be recycled. However, it would be possible to separate the FP-4 from the plutonium/thorium stream by recovering the plutonium/thorium by hydriding. The FP-4 do not form stable hydrides and would remain in solution. 

The TcAl6 phase was shown to be isoslructural with MnAlf, and ReAle- TcAli2 exhibits the same structure as M0AI12 and ReAli2 [51]. No new intermediate phases were found to exist in alloys of technetium with rhodium, palladium or platinum. The solubility of technetium in these metals increases in the given sequence ]71]. The group Vlll transition elements Co, Ni, Rh, Pd, Ir. and Pt show extensive solid solubility in technetium metal at 1050 "C [72]. The solid solubility of technetium in nickel is... 

Rhodium is hardly dissolved by any acids, unless when alloyed with other metals. The best method of dissolving it is to frise it with bisnlphate of potash, w hen it forms a soluble double salt. Rhodium, from its great hardness, has been used to form the tips of metallic pens, which are said to last wonderfully. 

This system seems to be the only alloy to date whose hydrous oxide growth behavior under potential cycling conditions has been investigated.189 190 Burke and O Sullivan189 demonstrated that with an alloy containing 10% by weight of rhodium in platinum both components corroded on cycling between certain limits (0-1.5 V) in 1.0 mol dm-3 NaOH. However, while the platinum corrosion product was found to be soluble under these conditions the rhodium one was not—in fact the hydrous film developed on the surface in this case was apparently derived almost totally from the minor component in the alloy. 

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