286 M. Laugier's Exconinaiion 



even in hytlrochloio-nitric acid, and vvliicli I think is rliodiuni: 

 but I could not discover the least trace of palladium. This 

 metal, and the rhodium which generally accompanies it in 

 ores of platina, hai'dly form the two-hundredth part of them. It 

 is almost impossible to verify its existence when quantities so 

 small as those given to me are experimented upon, — that is to 

 say, on portions of a gramme. 



In another experiment, 2 decigrammes of the same speci- 

 men gave me 0"13 of platina, 0'G4< of oxide of iron, and traces 

 of copper, of osmium, and of iridium, the presence of which 

 it is easier to detect than that of palladium and of rhodium. 



In these two trials of the platina of Siberia I obtained very 

 nearly the same proportions ; and I experienced every time a 

 loss of nearly a seventh part of the quantity employed, the 

 cause of which I cannot understand. 



The second specimen weighed only 0*G7. Its more com- 

 plicated composition required a more careful examination. It 

 is in general formed of grains of the size of large pins' heads 

 a little flattened. It is to be remarked that these grains differ 

 in colour : some are gray, others of a pure wlnLe ; and others, 

 smaller and of a blackish-gray colour, are separated by the 

 magnet. These last formed but the tenth part of the specimen. 

 The white grains comjiose nearly the third part of it ; the graj- 

 are the most abundant. I took two decigrammes of the grains 

 on which the magnet had no action, and I treated them with 

 aqua-regia formed of the two concentrated acids, in the propor- 

 tion of onepart of nitricacid and twoparts of hydro-chloric acid. 



The first portion of acid was coloured brown, a second por- 

 tion brownish-red, a third portion dissolved nothing more. 

 There remained some small grains of a pure silver-white, 

 weighings centigrammes, or the quarter of the ore employed. 

 This residuum, remarkable for its brightness, is so likewise for 

 its hardness, and the force of cohesion which unites its particles. 

 These two pi'operties make it differ greatly in aspect from the 

 residuum or black jiowder generally obtained from the pla- 

 tina of Peru which has been treated with aqua-regia. Tliis 

 last, in smaller grains, is easily reduced to powder and is easily 

 attacked by nitre. The I'esiduum of the platina of Siberia is very 

 difficult to break by the hammer in flattening its grains a little, 

 which supposes a little ductility ; it cannot be pulverized, and 

 the nitre does not seem to act upon it. Three successive 

 treatments with nitre at a red heat neither diminished its hard- 

 ness nor its weight. I was obliged to have recourse to caustic 

 j)otash, and treat it three times in a silver crucible with three 

 grammes of this alkali, to attack completely the five centigram- 

 mes upon which the aqua-regia had not acted. 



The 



