less_ than is sufficient to
neutralize the acid in the remaining cupric sulphate, and I then bring the
solution to or near the boiling-point by introducing steam into it; the
arsenic is dissolved not in the same vessel as the copper salt, but in a
separate one. When the arsenic solution is fully heated, a small current
of it is allowed to flow into the vat containing the copper salts, and
brisk stirring is kept up in the vat. The emerald green is at once formed;
but if there should be the slightest formation of any arsenite, the flow
of the arsenic solution is at once stopped until every trace of the
arsenite has been converted; the arsenic solution is then allowed to flow
in again, with the same precautions as before; in this way a large batch
of emerald-green can he formed in one or two hours, without containing the
slightest trace of the arsenite. I keep the arsenic solution near the
boiling-point during the whole of the time it is flowing into the other
vessel. By varying the proportions of water I could either make it coarse
or fine, as I wished, which is an important matter to have complete
control over in its manufacture.

Two points of interest occurred to me during the time I was occupied with
the research, which I had not time to complete; one was whether the
aceto-arsenite can be formed, adopting the old method for its formation,
if there is more than a certain quantity of water; from some experiments I
made in this direction I was inclined to the opinion it could not. I have
already stated that emerald-green is soluble to a certain extent in acids,
and that it is formed in a more or less acid solution; consequently a
varying amount of the pigment is always lost by being dissolved in the
supernatant liquid. To prevent to a certain extent this loss I
precipitated the copper from it as arsenite; but I was not successful in
the few experiments I had time to make on this part of the subject of
reconverting the copper arsenite thus obtained into the aceto-arsenite by
the addition of acetic acid.--_Jour. of Science._

* * * * *

ANALYSIS OF ZINC ASH AND CALCINED PYRITES BY MEANS OF AMMONIUM CARBONATE.

In a recent issue of the _Chemiker Zeitung_ Dr. Kosmann has reported an
analytical method for the examination of zinciferous products; according
to this report, the ash and flue dust produced by the extraction of zinc
from its ore comprise:

1. Zinc dust, from the distillat