consequently a very permanent color. It has also been not unfrequently
stated that the injurious effects of this pigment are due to the arsenious
oxide volatilizing from the other constituents of the compound. This
volatilization would likewise cause a breaking up of the entire compound,
and would consequently cause a discoloration of the paper; but the
volatilization of this arsenic compound is in every respect most
improbable.

The injurious effects, if any, of this pigment must therefore be due to
its mechanical detachment from the paper; but has it ever been
conclusively proved that persons who inhabit rooms the wall-paper of which
is stained with emerald-green suffer from arsenical poisoning? If it does
occur, then the effects of what may be termed homoeopathic doses of this
substance are totally different from the effects which arise from larger
doses. During the packing of this substance in its dry state in the
factory, clouds of its dust ascend in the air, and during the time I had
to do with its manufacture I never heard that any of the factory hands
suffered, nor did I suffer, from arsenical poisoning. If there is any
abrasion of the skin the dust produces a sore, and also the delicate
lining of the nostrils is apt to be affected. It is in this way it acts in
large doses; I am therefore very skeptical as to its supposed poisonous
effects when wall-paper is stained with it.

Different methods are given in works on chemistry for the manufacture of
this pigment, but as they do not agree in every respect with the method
which was followed in English color factories some years ago, it will be
as well, for the full elucidation of the manufacture of this substance, to
briefly recite some of these methods before describing the one that was,
and probably is still, in use; and I will afterward describe a method
which I invented, and which is practically superior to any other, both in