[Footnote: NOTE.--Each of these determinations was accompanied by a
series of results in which the practical determinations obtained from
the method described were compared with the theoretical contents of the
solutions of the various elements. These, however, would take up too
much room for insertion in these columns.]
By ALEX. CLASSEN and M.A. VON REIS; translated by M. BENJAMIN, Ph.B.,
F.C.S.
Ever since the electrolytic method for the estimation of copper came
into general use, numerous chemists have endeavored to adapt this
peculiarly simple and elegant method to the determination of other
metals. According to the experiments which have been made up to the
present time, it has been found that the separation of copper is best
effected in a nitric acid solution, while that of nickel and cobalt
takes place most readily in an ammoniacal solution, and for the
precipitation of zinc and cadmium a potassium cyanide solution is the
best. The accuracy of the results depend chiefly upon the following of
certain fixed rules, such as, for instance, that the precipitation of
copper only takes place when there is a definite amount of nitric acid
in the solution; that of cobalt and nickel when a certain quantity of
ammonium hydrate and ammonium sulphate is present. The electrolytic
decomposition of the chlorides has not yet been successfully
accomplished, so that prior to the operation it is necessary to convert
them into sulphates. The experiments which have been made for the
purpose of investigating the application of the electric current in
quantitative analyses are very few, about the only exception being the
separation of copper from the metals which are not precipitated from a
nitric acid solution, or which are deposited as peroxides at the other
electrode. We shall endeavor to show in that which follows, that copper,
zinc, nickel, and cobalt, and even iron, manganese, cadmium, bismuth,
and tin, whether they be present as sulphates, chlorides, or nitrates,
may be precipitated and separated from each other by electrolytic
methods much more rapidly than by any previously known process.