406 E. W. CHALLINOR. 



The APPROXIMATE COLORIMETRIC ESTIMATION 



OF NICKEL and COBALT in PRESENCE of 



ONE ANOTHER. 



By R. W. Challinor. 



[Communicated by Acting Professor J. A. Schofield, 



f.i. a, F.C.S., A.R.S.M.] 



[Read before the Royal Society <>/ A*. S. Wale*, December 7, 1904.'] 



Maumene about 1851 appears to have first observed that 

 the colours of solutions of Xi and Co are complementary, 

 hi^ experiment being quoted by Rudolph Wagner in 1854. 1 



Dr. 0. Winkler in 1866 2 published a method, founded on 

 Maumene's observation, for the colorimetric estimation of 

 Ni and Oo, but the method does not seem to have been 

 used, probably owing to his experiments being few in num- 

 ber and the method somewhat complicated. 



Dr.Wolcott Gibbs made useof the complementary colours 

 of the Ni and ) solutions, to remove the colour from a 

 solution of either metal when testing for Mn in its presence 

 by the PbO, and UNO, method. 



W. Gould Leison 4 also used the same method to avoid 

 the colour interference when estimating Ni or Co by titra- 

 ting the oxalates with KMn0 4 . 



J. Shiiller 5 estimated Ni in Ni steels by removing iron and 

 comparing the Ni solution with a Ni solution of known Ni 

 content. He states that steel containing under If Ni gives 

 too faint a colour for estimation by this method. 



1 Journal fur Practische Chemie, 61, 129. 

 * hoc. cit., 97, 414. 



3 Amer. Journ. Sci., Series 2, Vol. xin., p. 204. 



4 Chemical News, Vol. xxn., p. 210. 



5 Chem. Zeit., 1897, xxi., pp. 243 - 244. 



