SEPARATION OF IRON FROM NICKEL AND COBALT. 163 
6, 7, 8 and 9, Table II. the lead sulphate precipitated from 
the boiling solution by 50 cc. of 5 HK. HeSO:; was filtered 
off without expelling the nitric acid. After adding an 
excess of ammonium hydrate these filtrates were electro- 
lysed. 
Standard Solutions of the nitrates of iron, nickel, and 
cobalt were prepared :— 
Nitrate of iron from iron wire containing °077} of carbon. 
Nitrate of cobalt: 25 grams. of cobait sulphate and 50 
grams of ammonium sulphate were dissolved in water, made 
very slightly acid, sulphuretted hydrogen passed through 
the solution and the resulting precipitate removed. The 
filtrate was made alkaline with ammonium hydrate, and 
boiled for a long time in order to remove the iron as ferric 
hydrate. On electrolysis this solution gave a dull grey 
firmly adherent deposit which was weighed, dissolved in 
nitric acid and the solution made toa known volume. This 
purification would give a cobalt nitrate sufficiently free 
from all impurities, excepting nickel. 
Nitrate of nickel’ was prepared similarly. The flasks 
and pipettes used were calibrated against calibrated 
weights. Judging from the greatest difference between 
the values obtained for any one pipette in this testing the 
amounts of cobalt and nickel ‘taken’ are never inaccurate 
by more than + ‘0001 grm. 
The equation for the reaction was found to be essentially 
3 PhO + 2¥Fe (NO:), Aq =3 Pb (NO;). + Fe.O; Aq. 
Thus the lead oxide used should be at least six times the 
weight of iron to be precipitated. In each of the test 
analyses, slightly more than six times as much lead oxide 
was used. An excess of 20 cc. of 17 KH. ammonium hydrate 
was used in each electrolysis. 
entirely absent from electrolytically. deposited Ni, Fe, and Co in same 
proportion as unrefined material. 
