208 M. Berzelius on the [March, 



nickel absolutely free from cobalt, by slowly evaporating an 

 aramoniacal solution of the oxalates of nickel and of cobalt. The 

 oxalate of nickel is deposited, and that of cobalt remains dis* 

 solved in the form of a double oxalate of cobalt and ammonia. 

 But tliis process, as M. Laugier observes, cannot be employed 

 in an analysis. 



Dr. Thomson proposes, in order to obtain pure nickel, to 

 dissolve the ore of»this metal in a mixture of sulphuric and 

 nitric acid, which leaves the greater part of the arsenious acid 

 undissolved : to the filtered solution, potash is to be added, and 

 then the double sulphate of nickel and potash is to be crystal- 

 lized. By this method the arsenic is separated, for the crystals 

 do not contain any ; but if the ore contains cobalt, zinc, and 

 copper, these metals also form double salts with potash which 

 are not separable by crystallization from that of nickel. Added 

 to this, Dr. Thomson's method is not apphcable to analysis. 



It is to M. Stromeyer that we are particularly indebted for a 

 knowledge of the composition of nickel ores. It is he also who 

 informed us that wodanium and vestium are not pecuhar metals ;* 

 but he has not yet, as far as I know, described the analytic 

 method by which he obtained his results. This circumstance is 

 nevertheless extremely important ; for without it, the probability 

 of the result depends entirely on the confidence which is placed 

 in the author. 



M. Berthier has given us analyses of an arseniuret and of ari 

 arseniate of nickel. We owe to him a very good process for 

 determining the quantity of arsenic acid in a solution deprived 

 of insoluble bases. It consists in dissolvino; a s^iven weisrht of 

 iron m nitric acid ; this solution is to be poured into the liquid 

 from which the arsenic acid is to be separated, and precipitated 

 by means of ammonia. The precipitate formed is subarseniate 

 of iron, which after being heated is to be washed, and the quan- 

 tity of arsenic acid is discovered, because that of the oxide of 

 iron was previously known. 



M. Psaff, of Kiel, has lately examined the same ore of nickel, 

 which is the principal subject of this memoir. The observations 

 which I have already made upon the ancient methods of analyz- 

 ing' these ores are for the most apphcable to that selected by 

 M. Psaff, and which I consider it useless now to describe. He 

 found this ore to consist of 



Nickel 24-42 



Arsenic 45*90 



Iron 10-46 



Sulphur 12-36 



Loss 6-86 



* That vestium is not a peculiar metal was also shown by IMr. Faraday in the Royal 

 Institution Journal, vol. 6. p. 112 but whether before or {rfter M. Stromeyer, I do not 

 know.— £rf. 



