188 Biographical Account of Br. Wollastox, ly Dr. Thomas Thomson. 



employed in chemical experiments and analysis, its immense importance 

 in chemical researches hecame at once obvious. 



But native platinum is a compound or mixture of eight diflFerent metals. 

 It was necessary to get rid of these foreign bodies before converting pla- 

 tinum into bars. He dissolved crude platinum in nitro-muriatic acid, 

 filtered, and precipitated the platinum by sal-ammoniac. The yellow pre- 

 cipitate was carefully washed, and heated very cautiously in a black lead 

 crucible to drive off the sal-ammoniac. The grey residue is platinum. 

 It is rubbed to powder by the hand, and then triturated by a wooden 

 pestle in a wooden mortar, care being taken to do nothing that would 

 polish the edges of the platinum powder, because that would prevent the 

 welding process from taking place. The powder is now put into a brass 

 mould, filled with water, taking care that no vacuities are left. The top 

 of the powder is covered first with paper and then with cloth, and it is then 

 compressed with the force of the hand by a wooden plug. After this a 

 circular plate of copper is placed on the top, and it is exposed to a very 

 violent pressure in a horizontal press. It is then put into a charcoal fire 

 and heated to redness, to drive off the water. 



The ingot of platinum thus formed is placed upon an earthen stand, 

 about 2J inches above the grate of a wind furnace. The ingot is placed 

 on its end, and is exposed for twenty minutes to the highest temperature 

 that can be raised in the furnace. It is now placed on an anvil, and 

 struck while hot on the top with a heavy hammer, so as at one heating 

 effectually to close the metal. It must never be struck on the sides, 

 which would cause it to crack. By this hammering it is brought into the 

 state of a perfect ingot fit for all purposes. 



During Dr. Wollaston's experiments on crude platinum, he discovered 

 a new metal, to which he gave the name oi palladium, or new silver. In 

 the year 1803 he drew up a statement of the most remarkable and char- 

 acteristic properties of palladium. This statement, together with some 

 specimens of the metal, was exhibited in the windows of some shops in 

 London, without the least hint of who the discoverer was, or from what 

 source the metal was obtained. This very uncommon mode of exhibiting 

 a chemical discovery, naturally led Mr. Ghenevix to suspect that the pre- 

 tended new metal was nothing else than an artificial compound of some 

 metals previously known. He purchased, accordingly, all the specimens 

 of palladium exhibited in London for sale; and after an elaborate and 

 laborious course of experiments, drew up a paper on the subject, in which 

 he showed that it was an amalgam of platinum, or a compound of mer- 

 cury and platinum. This paper was read at a meeting of the Eoyal 

 Society, and unless I am mistaken, Dr. Wollaston himself was the person 

 that read it to the Society. 



Chenevix's paper was not only read to the Royal Society, but published 

 in their transactions for 1803, without any information afforded that the 

 metal called palladium had been discovered and examined by Dr. AVol- 

 laston On taxing Dr. Wollaston with cruel and unhandsome conduct 



