62 Qualitative Tests. 
Interfering Elements. 
Arsenic.—Roast and scorify with successive addi- 
tions of borax. There may be, in order given: Yellow 
(iron), green (iron and cobalt), blue (cobalt), reddish 
brown (nickel), green (nickel and copper), blue (cop- 
per). | 
Copper and other Elements which Color Strongly. 
—Fuse with borax and lead in coal in R. F. The borax 
on platinum wire in O. F. will show the cobalt, except 
when obscured by much iron or chromium. 
Iron, Nickel, or Chromium.—Fuse in R. F. with 
a little metallic arsenic, then treat as an arsenide. 
Sulphur or Selenium.—Roast and scorify with bo- 
rax, as before described. 
IN THE WET WAY. 
1. Fixed alkalies precipitate blue basic salts. This 
precipitate absorbs oxygen and becomes olive-green hy- 
droxide. If boiled before oxidation in the air becomes’ 
rose-red Co(OH):; does not dissolve in excess. HN« 
OH produces the same precipitate, which is soluble in 
excess. 
2. KsFeCceNe precipitates dark brown Cos(FeCs 
Ne):, insoluble in HCl. If to a solution of Co or Ni an 
excess of NH:Cl and NH:OH is added and then KsFe 
OcNe, a blood-red color indicates Co. If Ni is present, 
and the solution is boiled, a copper-red precipitate 
forms ; if any Co is present, a dirty green, on boiling. 
3. To a dilute solution of cobaltous nitrate add 
tartaric or citric acid, then an excess of ammonia, and 
a few drops of potassium ferricyanide; a deep-red color 
appears, even if largely diluted. 
Confirm.—By blowpipe test. 
