It was in attempting to analyse this second metallic precipitate,
that he that discovered palladium. After separating from it a quan-
tity of lead, and some iron by muriatic acid, and dissolving out some
copper by dilute nitrous acid, he was endeavouring to extract the
remainder of the copper by a stronger nitrous acid, when he remarked
that the colour of the solution, instead of being blue, as before, turned
to a dark brown, in consequence of the solution of some other me-
tallic ingredient. The first thought which occurred to him was, that
some iron had remained, and had communicated this colour to the
solution: but when he considered that this substance had been more
slowly acted upon than copper, he relinquished that hypothesis, and,
endeavouring to precipitate thevmetal by a clean plate of copper, he
obtained a black powder, which was redissolved in nitrous acid, and
formed a red solution.
The solubility of this precipitate in nitrous acid, showed that it did not consist either of gold or platina: the colour of the solution proved equally that it was neither silver nor mercury; and since the precipitation by copper excluded the supposition of all other known metals, he presumed that he “as engaged with a new metallic body, but was not fully satisfied of its existence until he had afterwards precipitated it by mercury, with which it formed an amalgam. By treating this amalgam he procured, in a pure state, the metal to which he afterwards gave the name Palladium, from the planet which had been discovered, nearly at the same time, by Dr. Olbers.
There were various considerations arising out of the preceding ex- periments, which induced him to consider this as a new simple metal; but since it was possible he might be deceived, he undertook a course of experiments for the purpose of obviating all possible objections. He formed alloys with many different metals, dissolved it in various acids, and. having recovered it from the alloys and solutions so formed, he found it to remain unaltered, retaining its original pro-= perties, being nearly infusible by itself, but easily fused with sulphur, with arsenic, or with phosphorus; soluble in nitrous acid, and pre- cipitated from thence by green sulphate of iron, by muriate of tin. by prussiates, and by hydro-sulphurcts.
When he found all his endeavours to decompose this substance ineffectual, he became more confident of its being a new simple metal, and accordingly published a concise delineation of its cha- racter, but avoided directing the attention of chemists to the source from whence it had been obtained, and thereby reserved to himself a more deliberate examination of many phenomena that yet remained unexplained in the analysis of platina, by which he was subsequently led to the discovery of rhodium, another metallic substance. already published in the last volume of our Transactions.
