Iridium arsenate

Iridium Arsenate is said14 to be precipitated when sodium orthoarsenate is added to a hot solution of iridium chloride. 

Like iridium, arsenic is enriched in Cretaceous-Tertiary boundary shales from New Zealand (Brooks et al., 1984 Strong et al., 1987). The iridium is believed to have originated from an asteroid impact that caused the massive extinction at the end of the Cretaceous period about 65 million years ago. In contrast, most of the arsenic in the boundary shales probably had a terrestrial origin (Strong et al., 1987). The extinction of marine organisms, especially plankton, from the impact may have been responsible for increased anoxic conditions in the oceans, which led to the precipitation of arsenic in the marine deposits (Brooks et al., 1984), 541. 

Nitric acid reacts with all metals except gold, iridium, platinum, rhodium, tantalum, titanium, and certain alloys. It reacts violentiy with sodium and potassium to produce nitrogen. Most metals are converted iato nitrates arsenic, antimony, and tin form oxides. Chrome, iron, and aluminum readily dissolve ia dilute nitric acid but with concentrated acid form a metal oxide layer that passivates the metal, ie, prevents further reaction. 

Although trialkyl- and triarylbismuthines are much weaker donors than the corresponding phosphoms, arsenic, and antimony compounds, they have nevertheless been employed to a considerable extent as ligands in transition metal complexes. The metals coordinated to the bismuth in these complexes include chromium (72—77), cobalt (78,79), iridium (80), iron (77,81,82), manganese (83,84), molybdenum (72,75—77,85—89), nickel (75,79,90,91), niobium (92), rhodium (93,94), silver (95—97), tungsten (72,75—77,87,89), uranium (98), and vanadium (99). The coordination compounds formed from tertiary bismuthines are less stable than those formed from tertiary phosphines, arsines, or stibines. 

Antimony, arsenic, selenium, tellurium, iridium, iron, molybdenum, osmium, potassium, rhodium, tungsten (and when primed with charcoal,) aluminium, copper, lead, magnesium, silver, tin, zinc. Interaction of lithium or calcium with chlorine tri- or penta-fluorides is hypergolic and particularly energetic. 

Antimony, arsenic, bismuth, cadmium, calcium, cesium, chromium, cobalt, copper, gold, indium, iridium, iron, lead, lithium, magnesium, manganese, mercury, nickel, palladium, platinum, potassium, rhodium, rubidium, ruthenium, selenium, silver, sodium, tellurium, thallium, zinc... 

The most active catalyst is platinum applied in finely divided form, for example platinised asbestos. Certain elements, especially arsenic and mercury, have a powerful effect in reducing the activity of the platinum, a quantity of arsenic equal to 0-2 per cent, of the weight of the platinum reducing the activity by 50 per cent.5 These poisons, as they are termed, also include less harmful substances such as antimony, lead, bismuth, etc. The presence of small quantities of rhodium, iridium or osmium in the platinum also causes diminished yields of trioxide, but the presence of palladium or ruthenium has the opposite effect.6... 

Of the 19 elements determined in Sasanian silver objects, only gold and iridium seem to indicate the silver source used. Indirectly through their concentration ratios zinc, tin, arsenic, antimony, and selenium might provide some additional information on the silver source used, and their absolute concentrations, together with those of other elements might be useful in obtaining information on metallurgical techniques used. 

Iridium Arsenide, IrAs2, has been obtained in a pure form by heating iridium chloride with an excess of arsenic in a current of hydrogen.4 It is also formed when an intimate mixture of the finely divided metal and excess of arsenic is heated in an indifferent atmosphere. The arsenide may be analysed by the method described under palladium arsenide (p. 73). 

The ligands triphos or/ and np in presence of compounds of iron, cobalt, nickel, rhodium, iridium and palladium, by reaction with THF solutions of white phosphorus, P, or yellow arsenic, As, form mononuclear or dinuclear sandwich complexes containing the cyclo-triphosphorus or cyclo-triarsenic units which behave as 3n-electrons rings. 

Ivandini, T. A., Sato, R., Makide, Y., Fujishima, A. and Einaga, Y. (2006b), Electrochemical detection of arsenic(III) using iridium-implanted boron-doped diamond electrodes. Anal. Chem., 78(18) 6291-6298. 

Gold Iridium Platinum Rhodium Ruthenium Palladium Mercury Silver Osmium Selenium Tellurium Polonium Copper Technetium Bismuth Antimony Arsenic Carbon Lead Rhenium Nickel Cobalt... 

The solution niay contain Pt,Ir and Au, contaminated with As, Sb and Sn. HC1 is added and the precipitated sulphides fused with Naa C03-f-Na3N03. Extraction with water removes As as soluble arsenate.The residue is reduced with Zn + HC1. Boiling with HC1 dissolves out the Sn. Again boiling with HN03 and tartaric acid removes Sb. The residue is heated to dull redness to render iridium insoluble. Dilated aqua regia is added. 

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