208 



It was in attempting to analyse this second metallic precipitate, 

 that he first 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 the metal 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, lie presumed that he was 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 w T ith 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-sulphurets. 



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. 



