Iridium history

Hardness of the aimealed metals covers a wide range. Rhodium (up to 40%), iridium (up to 30%), and mthenium (up to 10%) are often used to harden platinum and palladium whose intrinsic hardness and tensile strength are too low for many intended appHcations. Many of the properties of rhodium and indium. Group 9 metals, are intermediate between those of Group 8 and Group 10. The mechanical and many other properties of the PGMs depend on the physical form, history, and purity of a particular metal sample. For example, electrodeposited platinum is much harder than wrought metal. 

The earliest scientific descriptions of platinum, are those of Dr. Brownrigg and Don Antonio de UUoa in the middle of the eighteenth century. Rhodium, palladium, osmium, and iridium were discovered in 1803 and 1804, the first two by Dr. Wollaston and the others by his friend, Smithson Tennant. Thomsons History of Chemistry and Berzelius correspondence and diary present a pleasing picture of these two great English chemists. Ruthenium, the Russian member of the platinum family, was discovered much later by Karl Karlovich Klaus, whose life story was beautifully told by Professor B. N Menschutkin of the Polytechnic Institute of Leningrad. 

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... 

Occurrence and History.—Osmium occurs in nature alloyed with iridium as iridosmine or osmiridium, which is found as irregular flattened grains and, more rarely, as hexagonal prisms. It has a metallic lustre, tin-white to light steel-grey in appearance hardness 6-7 density 19-3 to 21-12.1 It occurs in Choco, South America in the Urals in auriferous and other drifts in New South Wales in auriferous beach-sands of North California and also in gold washings of certain Canadian rivers.1... 

Occurrence and History.—Iridium is found in nature alloyed with platinum or other allied metals, particularly in platiniridium and osmiridium (see analyses, pp. 208, 258). Nevyanskite, a variety of osmiridium, contains over 40 per cent, of iridium, whilst siserskite, another variety, contains up to 80 per cent, of the same metal.1... 

Occurrouoo and History of Iridium—Preparation—Purilieation -Physical and Chemical Properties—Atomic Weight—Usos—Alloys. 

It will be observed that all of the meteorites contain, in addition to nickel, a small quantity of cobalt, whilst the carbon content is extremely small. Carbon is sometimes present in meteoric iron in the form of minute diamonds.2 The Rowton specimen is interesting as being the first sidente observed to fall in Great Britain, and may be seen in the Natural History Museum, South Kensington. The Perryville siderite is the first recorded instance of the presence of ruthenium in meteoric iron. In addition to traces of this element, traces of iridium, palladium, and platinum were detected. 

Two kinds of metal are found in chondrites grains composed of refractory elements (iridium, osmium, ruthenium, molybdenum, tungsten, and rhenium), which condense along with the refractory oxides above —1,600 K at 10 atm, and grains composed predominantly of iron, cobalt, and nickel, which condense with forster-ite and enstatite at —1,350-1,450 K. The former are associated with CAIs (Palme and Wlotzka 1976) and the latter with chondrules, typically type I or FeO-poor chondrules (B J 1998, pp. 244-278). Unfortunately, few chondrites preserve a good record of the formation history... 

The use of catalytic methods for the technical preparation of agrochemicals is illustrated by the case history of the herbicide metolachlor (trade name DUAL ), the most important herbicide for maize. The key step for the technical synthesis of the racemic conqx>und is a reductive alkylation catalyzed by a Pt/C catalyst in presence of sul ric acid. The commercial production of the biologically active S-enantiomers was made possible by the development of a new Iridium ferrocenyl-diphosphine catalyst system. Inqxirtant aspects of the development of the two catalyst systems as well as important prerequisites for the use of catalysts for the production of agrochemicals are discussed. 

Berthelot obtained ethyl peroxide from ether and ozone.He investigated photochemical reactions. His work on galvanic cells, partition coefficient, reaction velocity and equilibrium, and thermochemistry, is mentioned elsewhere. He analysed ancient metallic and other objects from Egypt and Mesopotamia, showing that the earliest so-called bronzes were pure copper, that an ancient Sumerian vase was of pure silver, and a box from Egypt was in part platinum-iridium. This work laid the foundations of chemical archaeology. His fundamental work on the history of chemistry is dealt with in Vol. I. One of his most important early researches, on glycerine, has been left over for consideration and will now be taken up. 

History. Osmium was discovered in 1803 by Smithson Tennant in the dark colored residue left when crude platinum is dissolved by aqua regia. This dark residue contains both osmium (named after the Greek osme, meaning odor) and iridium. It is a bluish-white, silvery, extremely hard brittle metal that is not malleable even at high temperatures. 

NAA has been used in many applications. One very special one is the determination of the iridium content in the earth s cmst and in a 1-cm thick clay layer round the earth. This day layer was formed 65 million years ago and defines the boundary between the Cretaceous and the Tertiary pericxls of geological history. Shells offoraminifera are found in all marine environments and in abundance in the limestone above and below the spedal day layer. But not in the layer itself. In addition it was shown by NAA that the iridium content of the limestone layers above and below is 0.3 ppb while the concentration in the layer is 10-40 pbb. This is the source of the theory of a giant asteroid collision with the earth at this time, a collision that brought the end of the dinosaur era. 

For the motivation for and a short history of the satellite-based personal communication services, see Sweeney (1993), Dwyre (1998), Jung, Wamecke (1998, pp. 4-148). About the failed Iridium venture see Feder (2000), Grimes (2000). 

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