Descotils

Iridium - the atomic number is 77 and the chemical symbol is Ir. The name derives from the Latin Iris, the greek goddess of rainbows because of the variety of colors in the element s salt solutions . Iridium and osmium were both discovered in a crude platinum ore in 1803 by the English chemist Smithson Tennant. Iridium was discovered independently by the French chemist H. V. Collet-Descotils also in 1803. Descotils actually published one month before Tennant but Tennent is given credit for the discovery, perhaps because he alone also found osmium in the ore. 

It was there that he discovered a new metal which, because of the red color that its salts acquire when heated, he named erythronium (44). Upon further study, however, he decided that he was mistaken, and that the brown lead ore from Zimapan was a basic lead chromate containing 80.72 per cent of lead oxide and 14.80 per cent of chromic acid (12). His paper therefore bore the modest title, Discovery of chromium in the brown lead of Zimapan (21). In 1805 Collet-Descotils confirmed del Rio s analysis (22), and for twenty-five years no more was heard of the new element, erythronium. 

Collet-Descotils, H.-V., Analyse de la mine brune de plomb de Zimapan,... 

Another circumstance which helped to shake del Rio s confidence in his own work was the analysis of this mineral which H.-V. Collet-Descotils, a friend of Vauquelin, published in 1805 (13). When Collet-Descotils concluded that the supposed new metal was merely chromium, del Rio warmly defended his own prior claim to the discovery of chromium in the brown lead ore (14). 

The details of N. G. Sefstrom s discovery of vanadium in soft iron from the Taberg Mine in Smaland, Sweden, and of F. Wohler s proof of the identity of erythronium and vanadium have already been related (14, 15, 16). Dr. Enrique Moles emphasized the fact that del Rio s own excessive modesty and scientific caution led him to renounce the discovery of the new element before the analysis of Collet-Descotils had been published. 

Tennant investigated it carefully m an attempt to alloy lead with it, and concluded that it contained a new metal (17). In the autumn of the same year H.-V. Collet-Descotils, a friend and pupil of N.-L. Vauquelin, found that this powder contains a metal which gives a red color to the precipitate from an ammoniacal platinum solution (18). When Vauquelin treated the powder with alkali he obtained a volatile oxide which he believed to be that of the same metal with which Descotils was dealing (19). 

Two memoirs were afterward published in France [continued Tennant] one of them by M. Descotils and the other by Messrs. Vauquelin and Fourcroy. M. Descotils chiefly directs his attention to the effects produced by this substance on the solution of platina. He remarks that a small portion of it is always taken up by nitromuriatic acid during its action on platina and, principally from the observations he is thence enabled to make, he infers that it contains a new metal, which, among other properties, has that of giving a deep red colour to the precipitates of platina. M. Vauquelin attempted a more direct analysis of the substance, and obtained from it the same metal as that discovered by M. Descotils, But neither of these chemists have observed that it contains also another metal, different from any hitherto known.. . . ... 

Tennant gave the name iridium to the metal which Descotils and Vauquelin had observed, and the name osmium to the new one (20). In speaking of iridium, osmium, palladium, and rhodium, W. T. Braude stated in his lectures in 1817, Of these, the two former were discovered by the late Mr. Tennant and the two latter by Dr. Wollaston and bad we searched throughout chemistry for an illustrative instance of the delicacy of the modem art of analysis, it would be difficult to have found any one more notorious than the history of the discovery and separation of these bodies exhibits (46). During the entire course of the researches which led to ibe discovery of these four metals, Dr. Wollaston and Tennant had friendly intercourse with each other, and each kept in close touch with... 

Other members of the group are iridium, discovered by Tennant in 1804, used in combination with platinum in the construction of pyrometers, and as pure metal for tipping gold pens osmium, discovered by Descotils in 1803, and by Tennant in 1804, used in the... 

Tennant began in 1803 to work on the residue remaining when crude platinum is dissolved in aqua regia, and believed then that it contained a new metal. Fourcroy and Vauquelin, and Collet-Descotils, simultaneously concluded that the solution of crude platinum contains a new metal, and they should rank with Tennant as independent discoverers of iridium. 

Clouet — Bucquet — D Arcet — Collet-Descotils — Sigaud de la Fond — Seguin — Adet — Hassenfratz — Lagrange. 

Four years later, in 1805, the Collet-Descotils examined what was supposed to be the metal, stating it was just an impure chromium oxide. Del Rio apparently accepted this conclusion. In 1830 the Swedish chemist N.G. Seftroem discovers a new metal which he named VANADIUM. This metal was described by Berzelius in 1831, as follows ... 

But CoUet-Descotils was wrong. The presumed new metal was not chromium. It was new One of the samples of the brown lead mineral that von Humboldt had sent to Europe had found its way to Friedrich Wohler. He found that the Zimapin mineral contained a new element and that Del Rio in fact had been right in his first analytical results. Various circumstances had, however, delayed Wohler s investigation and the result was not published until 1831. In the previous year. Nils Gabriel Sef-strom in Sweden had discovered the same element in an ore from Sm41ands-Taberg and given it the name vanadium. 

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