ON PALLADIUM. J27 



Jn endeavouring to diflblve a piece of palladium, in flrong Palladlu* is 



Colourlefs nitric acid for the purpofe of formins^ the detonatinj^ very flowly ^ 



• f^ & r> adied on by ni- 



pruffiate, I found that, although the acid fliortJy acquired a red trie acid and «- 

 colour furrounding the metal, the a6lion of the acid was ex- tncatano gas. 

 tremely ilow, and I was furprifed to obferve a fa6l that appears 

 to me wholly fingular: the metal was taken up without any 

 extrication of nitrous gas ; and thi.« feemed to be the caufe of 

 the flow folution of this metal, as there was not that circula- 

 tion of this fluid, which takes place in the folution of other 

 metals until the acid is nearly faturated. 



As the want of production of gas appeared to retard the folu- Nitrous acid a£ls 

 tion of palladium, I tried the GffeS. of impregnating a quantity °'^ ' ^^ 

 of the fame acid previoufly with nitrous gas, and obferved its 

 a6tion to be very confiderably augmented, although the expe- 

 riment was neceflarily tried in the cold, becaufe the gas would 

 have been expelled by the application of heat. 



Befide thofe properties which are peculiar to palladium there 

 are others, not lefs remarkable, which it pofl!efles in common 

 with platina. I have on a former occalion mentioned that thefe 

 metals refemble each other in deftroying the colour of a large . , 



quantity of gold. Their refemblance, however, in other pro- 

 perties is not lefs remarkable, more efpecially in the little 

 power they pofTefs of conducting heat, and in the fmall degree 

 of expanfion to which they are liable when heated. 



For the purpofe of making a comparifon of the conducing Conducing 

 power of difFerent metals, I endeavoured to employ them in P?*'"" °/ P^'j^* 



*. 1 r 1 duim and platina 



fach a manner, that the fame weight of each metal might ex- as t» hear, tried 

 pofe the fame extent of furface. With that view I feledted **>■ ^"^ "■ it'"S 

 pieces of filver, of copper, of palladium, and platina, which had them. The 

 beeii laminated fo thin as to weigh each 10 grains to the fquare meafure is not 

 inch. Of thefe I cut flips ,'^ of an inch in breadth, and four fjyer andcop- 

 inches long ; and having covered their furfaces with wax, Ipe^* 

 heated one extremity fo as to be vifibly red, and, obferving 

 the diftance to which the wax was melted, I found that upon 

 the filver it had melted as far as 3^ inches: upon the copper 2| 

 inches : but upon the palladium and upon the platina only one 

 inch each': a difl'erence fufficient to eflablifli the peculiarity of 

 thefe metals, although the condudling power cannot be faid to 

 be limply in proportion to thofe diftances. 



In order to form fome eftimate of the comparative rale of Rate of expan. 

 expanfion of thefe metals, I rivette^ together two thin plates of ^^.j"^^*' ^"gttjng 

 L 2 platina bars tog«thtr. 



