NICKEL 415 



whole allowed to stand for 12 or 18 hours, and frequently agitated. The precipi- 

 tated superoxide of cobalt, and the excess of carbonate of baryta, are well washed 

 with cold water, and dissolved in hot hydrochloric acid ; after the separation of the 

 baryta by sulphuric acid, the cobalt is precipitated by hydrate of potash, and, after 

 being washed and dried, is reduced in a platinum or porcelain crucible by hydrogen 

 gas. The fluid filtered from the superoxide of cobalt is of a pure green colour. It is 

 free from any trace of cobalt. After the removal of the baryta by means of sulphuric 

 acid, the oxide of nickel is precipitated by caustic potash. Even this method did 

 not give exact results on the first trial. 0'318 gr. metallic nickel and - 603 gr. 

 metallic cobalt were employed, and 0'430 gr. oxide of nickel and 0-580 gr. cobalt 

 were obtained : 



Employed 



Nickel 84-53 



Cobalt 65-47 



100-00 9973 



The cause of these incorrect results is, that the solution was filtered an hour or 

 two after the precipitation of the superoxide of cobalt by the carbonate of baryta. 

 It is necessary, however, to wait a considerable time, at least 12 hours, or even 

 18 is better, and allow the excess of carbonate of baryta to remain in contact 

 with the solution, as the superoxide of cobalt is precipitated very slowly : this 

 explains the diminution of the cobalt and increase of the nickel in the above expe- 

 riment. 



It will be readily perceived that not only cobalt, but also other metals, as iron and 

 manganese, may be separated from nickel by this method. On the other hand, oxide 

 of cobalt may be separated from the oxide of zinc, and other strongly basic oxides, 

 which are not converted into superoxides. Nickel and cobalt can, moreover, be sepa- 

 rated from metals to which they bear a close analogy in various ways. 



From nickel, manganese may be best separated in the same manner as cobalt. 

 Manganese may be separated from both of them, however, by a method which, in its 

 essential parts, was proposed by Wackenroder. It is based upon the fact that, 

 although nickel and cobalt are not precipitated from their solutions by sulphuretted 

 hydrogen, especially when they are slightly acid, still the sulphides .precipitated by 

 hydrosulphate of ammonia are hot dissolved by very dilute hydrochloric acid. When 

 the oxides are contained in an acid solution (which should not contain nitric acid, 

 however), it is made ammoniacal, and they are precipitated as sulphurets by hydro- 

 sulphate of ammonia. Very dilute hydrochloric acid is then added to the solution, 

 until it has a very slight acid reaction ; the sulphides of nickel and cobalt remain 

 undissolved ; they are washed with water containing a little sulphuretted hydrogen 

 and a trace of hydrochloric acid. The sulphide of manganese is dissolved with 

 facility, but, although the fluid filtered from the sulphides of nickel and cobalt gives 

 only a rather dirty flesh-coloured precipitate on the addition of ammonia and hydro- 

 sulphate of ammonia, still the sulphide of manganese contains small portions of 

 sulphide of cobalt or nickel ; and when, therefore, it is treated anew with very dilute 

 hydrochloric acid, minute quantities of the black sulphides remain behind. By this 

 repeated treatment a very nearly correct separation may be obtained ; but the results 

 are more satisfactory in the separation of cobalt from manganese than of nickel from 

 the latter metal, evidently because nickel is not very perfectly precipitated by hydro- 

 sulphate of ammonia : 0'303 gr. of metallic cobalt and 0'385 gr. of binoxide of man- 

 ganese gave after the sulphide had been converted by aqua regia into oxide, and 

 this precipitated by hydrate of potash, and after the chloride of manganese dissolved 

 was free from sulphuretted hydrogen and precipitated by carbonate of soda 0'302 

 metallic cobalt and 0'392 oxide of manganese. 



0'251 gr. of oxide of nickel and 0'296 gr. oxide of manganese, treated in the same 

 manner, gave 0-214 oxide of nickel and 0'324 oxide of manganese. 



Iron also may be separated from nickel, and better still from cobalt, in the same 

 manner as manganese, since sulphide of iron, like sulphide of manganese, is easily 

 soluble in very dilute hydrochloric acid ; but in this case the resolution of the sul- 

 phide of iron is likewise necessary : 0'425 gr. metallic cobalt and 0-170 gr. sesqui- 

 oxideof iron, when treated in this manner, gave 0'414 gr. metallic cobalt and 0'172 gr. 

 sesquioxide of iron. 



For the details of processes which have been found useful in the separation of 

 nickel from other bodies, the reader is referred to "Watts's ' Dictionary of Chemistry.' 



Alloys of Nickel. Various alloys of nickel have been formed under different names ; 

 the following are a Few of them : 



