│ │ │ │ │ │ │ │ │ (_Nevyanskite_). California│ │ │ │ 2·60│53·50│43·40│ │ │Ru, 0·50 │ │ │ │ │ │ │ │ │ (_Nevyanskite_). “Austra- │ │ │ │ 3·04│58·13│33·46│ 0·15│ │Ru, 5·22 lia” │ │ │ │ │ │ │ │ │ (_Nevyanskite_). Currumbin,│ 3·00│ │ │ │62·00│33·00│ │ │Sand, 2·00 Q. │ │ │ │ │ │ │ │ │ (_Nevyanskite_). │ │ │ │ /\ │ │ │ │ Tasmania │ 0·37│ 0·30│ 0·21│ 33·80 │57·09│ tr. │ │Ru, 8·19; Au, ·04 │ │ │ │ │ │ │ │ (_Siserskite_). _Platin- │ │ │ │ │ │ │ │ │ iridium_ │ │ │ │ │ │ │ │ │ Condado, │55·44│ 4·14│ 1·49│ 6·86│27·79│ tr. │ 3·30│ │ Brazil │ │ │ │ │ │ │ │ │ _Native │ │ │ │ │ │ │ │ │ Iridium_ │ │ │ │ │ │ │ │ │ Urals │19·64│ │ 0·89│ │76·80│ │ 1·78│ │ ──────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴──────┴────────────────── Reference—Pt., platinum; Fe., iron; Pd., palladium; Rh., rhodium; Ir., iridium; Os., osmium; Cu., copper; Os-Ir., osmiridium; Ru., ruthenium. Footnote B: Average percentage of Urals platinum is a little under 80.[4] p. 558. Platinum is not acted upon by either nitric, sulphuric or hydrochloric acid, but is soluble in aqua regia (1 part of nitric to 2 parts of hydrochloric acid), or in other mixtures liberating chlorine, with the formation of platinum tetrachloride (PtCl_{4}). It is not acted upon by air or moisture, even at high temperatures. It is corroded by caustic alkalis, sulphides, sulphates, phosphates and arsenides, if heated in contact with them. It will not amalgamate with mercury unless sodium is present, in this respect differing from gold and silver. Platinum, in a finely-divided condition, absorbs large quantities of hydrogen or other gases, which on occlusion become more active: hence its value as a catalytic agent. _Palladium._—This metal resembles platinum, but is sometimes fibrous, the colour being between that of platinum and of silver. It possesses a lower melting-point than platinum—about 1550° C. It is malleable, has a hardness of from 4·5 to 5, and a specific gravity of 11·5. As already stated, palladium, when found in copper ores, is probably present in combination with arsenic. _Porpezite_, a rare mineral, containing gold and up to 10 per cent. palladium, has been identified in gold-bearing veins in Brazil [see p. 54]. Palladium is produced from the refining of copper matte and of base gold bullion from Australia and elsewhere.