Browning and Hartwell — Nickel from Cobalt. 317 



with strong sodium or potassinm hydroxide solution, in the 

 presence of an excess of potassium ferricyanide, a black flocky 

 precipitate formed which gave no test for ferro or ferricyanide, 

 and gave every indication of being nickelic hydroxide. This 

 reaction we found to afford us a most delicate test for nickel. 



The method as modified by us may be described as follows : 

 Dissolve not more than - l gm. of the salts of the two ele- 

 ments in about 5 cm3 of water, add a few drops of a saturated 

 solution of alum, destroy any free mineral acid by neutralizing 

 with ammonium hydroxide, and make faintly acid with acetic 

 acid. To this solution add about 0*5 grm. of potassium ferri- 

 cyanide and agitate to effect the solution of the ferricyanide 

 and the complete precipitation of the nickel and cobalt salts. 

 Then add about 5 cmS of strong ammonium hydroxide and filter. 

 To the filtrate, which should have no reddish color, add a piece 

 of sodium or potassium hydroxide about the size of a pea and 

 boil. The appearance of a black precipitate, in case of very 

 small amounts of nickel showing first as a dark coloration, 

 indicates nickel. 



The tables following give a record of the experimental 

 results. With the precautions indicated, this method may be 

 applied very satisfactorily. 









Table I. 



















NaOH, 







KA1(S0 4 ) 



2 





solid, 







NiS0 4 . 



saturated 





NH 4 OH 



about 





CoS0 4 7H 2 



7H 2 



sol. 



K 3 FeC 6 N 6 



(cone.) 



size ol 





grm. 



grm. 



cm 3 



grm. 



cm 3 



a pea. 



Result. 



1. 



o-oioo 



2 



0-5 



5- 



ic 



Heavy ppt, 



2. 



0-0050 



u 



u 



a 



te 



a 



3 



o-ooio 



a 



a 



a 



a 



a 



4 



0-0003 



C( 



a 



a 



a 



Distinct 



5 



o-oooi 



a 



a 



a 



u 



Plain 







Table II. 









1. o-io 







a 



a 



it 



a 



None 



2. 0-10 



o-oioo 



a 



a 



a 



a 



Heavy 



3. 0-10 



0-0050 



a 



a 



a 



a 



Distinct 



4. 0-10 



0-0030 



u 



a 



a 



a 



Very faint 



5. 0-05 







a 



a 



it 



a 



None 



6. 0'05 



o-oioo 



tt 



tt 



u 



u 



Heavy 



V. 0-05 



0-0050 



a 



a 



a 



(t 



Distinct 



8. 0-05 



0-0030 



u 



u 



<( 



a 



Plain 



9. 0-05 



o-ooio* 



u 



it 



l( 



a 



Faint 



* Equivalent to 0-0002 of the metal. 



