Ferrous sulphide was next similarly treated, and gave, after the lapse of a
few hours, a copious blackish precipitation of sulphur, and possessing
properties similar to the sulphur obtained by dissolving sulphides such as
cupric sulphide in dilute nitric acid, in all other respects resembling
common sulphur.

Phosphides of iron, zinc, etc., were next introduced, and gave, besides
carbon and other impurities, a residue containing a large percentage of
phosphorus, which differed from ordinary phosphorus with respect to its
insolubility in carbon disulphide, and which resembled the reaction in the
case with silicon-eisen rather than that of the boron compound, insomuch
that a large quantity of the phosphorus had passed into solution.

A rod of impure copper, containing arsenic, iron, zinc, and other
impurities, was next substituted, using hydrochloric acid as a solvent in
place of sulphuric acid. In the course of a day the copper had entirely
dissolved and precipitated itself on the negative electrode, the impurities
remaining in solution. The copper, after having been washed, dried, and
weighed, gave identical results with regard to percentage with a careful
gravimetric estimation. I have lately used this method, and obtained
excellent results with respect to the analysis of commercial copper,
especially in the estimation of small quantities of arsenic, thus enabling
the experimenter to perform his investigation on a much larger quantity
than when precipitation is resorted to, at the same time avoiding the
precipitated copper carrying down with it the arsenic. I have in this
manner detected arsenic in commercial copper when all other methods have
totally failed. I have also found the above method especially applicable
with respect to the analysis of brass.