The colorimetric determination of nickel. As Ni₍₄₎ dimethylglyoxime

Abstract

Abstract A description is given of a colorimetric determination of nickel as Ni (4) dimethylglyoxime, but in contrast to the customary methods, use is made of persulphate as oxidizing agent. The influence of other metallic ions has been investigated too. It appears that, of the elements investigated Ag must be removed, while the alkaline earth metals give a sulphate precipitate which can be removed by centrifuging. The determination of Ni in the presence of Mn, Fe, Cu and Co presents the greatest difficulties. In many cases we have succeeded finally in determining nickel in the presence of these elements without removing them. Thus it is possible to determine accurately 5% Ni and over in manganese, 0.25% and over in iron, 0.05% and over in copper and 0.05% and over in cobalt. In general it has been established that the highest accuracy is obtained when full attention is paid to the following points: the avoidence of ammonia the regulation of the amount of dimethylglyoxime the acidity of the solution. If one of these points is not in order, the degree of accuracy becomes less. This is the case in the determination of Ni in the presence of cobalt, copper, in which case the presence of ammonia is a necessary condition for the formation of the colour. It can be remarked that this method is extensively applied in our laboratory in the determination of Ni in chrome‐iron. Mo and W compounds.