348 Contributions to Chemistry from the 
This process answers extremely well for the analysis of nickel 
‘salts and gives more accurate results than the precipitation of 
the nickel as oxyd by caustic potash: it also requires less time 
since the sulphid may be washed with the greatest ease. On the 
other hand, as [ shall show, it is of very limited application as 
a means of separating nickel from other metals. The sulphid 
of nickel precipitated by heating with solution of hyposulphite 
of soda appears black at first, but after ignition has a dar 
bronze yellow color. It is unchangeable in the air, and may be 
boiled with strong chlorhydric acid without being sensibly at- 
tacked. Strong sulphuric acid exerts no action upon it: nitric 
acid oxydizes it to sulphate of nickel. It may be heated ina 
covered porcelain crucible without oxydation, but by roasting 
in a current of air is converted into a basic sulphate. For quan- 
titative purposes it is best, after washing and drying the sul- 
id, to burn it with the filter in a porcelain crucible so as: 
convert it into basic sulphate, to add to this a few drops of sul- 
phuric acid, evaporate to dryness and gently ignite the resulting 
neutral sulphate, from the weight of which the nickel may be 
calculated. The sulphate must be completely soluble in hot 
wate! se has shown that the sulphate may be completely 
converted into oxyd by strong ignition.’ 
ltj—The relations of cobalt to hyposulphite of soda are 
nary atmospheric pressure is almost impossible, In a seal 
tube, at a temperature of 120° C., the precipitation is cones 
ll cases, now- 
ever, it is best to treat the roasted sulphid with a few drops of 
sulphuric acid, evaporate and ignite gently. The cobalt (i) 
then be calculated from the weight of the sulphate. Cobalt 
by this process; as in the case of nickel, however, the nA 
completely precipitated together as sulphids b hyposulphite of 
soda at 120° C. ag is eat to weigh oth scaptbee as sulphates 
and then determine the cobalt by Stromeyer’s method as mo 
fied by Dr. Genth*, and myself; the oakel is then found by 
simply subtracting the weight of the sulphate of cobalt } 
that of the mixed sulphates. _ | 
* Pogg. Ann., cx, 132. * This Journal, [2], vol. xxiv, p- 86 
