68 F. W. Clarke on the separation of Cobalt and Nickel. 
1 find, sepals that the different properties of their ferricy- 
anids affor n easy means of distinguishing between these met- 
als. As is wal known, potassium | ferricyanid precipitates co- 
balt and nickel from their solutions, The cobalt precipitate is 
of a deep reddish brown color, while the nickel compound is of 
a dirty yellowish brown. The nickel ferricyanid, however, dis- 
solves with the greatest ease in ammonia water, or in solution 
of potassium cyanid, while the corresponding cobalt compound 
is absolutely insoluble in either. It is a noteworthy-fact, — 
ever, that the previous presence of either ammonia water or po- 
tassium cyanid, guisrely prevents the recipitaison of oasik 
whom I do n 
It is hears 2 : employ the ammonia to dissolve the nickel 
precipitate, since the presence of a cyanid agp the subse- 
quent detection of that metal rather diffic 
In an analysis I proceed as follows. To the slightly acid so- 
lution B yoniaining the two metals, I first add an excess of am- 
mon chlorid, This causes the cobalt precipitate, which 
eee would run through the filter, to fall in a denser state, 
cess of ammonia. Upon filtering, all the cobalt remains upon 
the filter, being recognized by the characteristic color of the 
precipitate, and the nickel is ee 3 detected in the filtrate, by 
means of ammonium sulphid, If, Seas filtering, the portion at 
first running through is turbid, it may be disregarded, or re- 
turned to the filter, ~ that which filters through subsequently, 
being almost invariably clear. 
I offer this process merely as a convenient means of detect- — 
ing cobalt and nickel in presence of each other in ordinary 
analyses. It is not particularly delicate, for, although the mi- 
erat trace of cobalt is detected, very small quantities of nickel 
willescape recognition. For exceedingly delicate work it is per-— 
haps better to employ some good quantitative process, but for 
ull ordinary —— I find this method very convenient, and 
t has been employed with success in the labo- 
ratory of oa Fey, and beginners have found no difii- 
culty in using 
Cornell . May 13th, 1869. 
