ion of this compound,
being generated, the writer thinks probable, "by the joint action of
moisture and organic matters, viz., of substances used in fixing to walls
papers impregnated with arsenic." In some of our chemical manuals, Dr.
Kolbe's "Inorganic Chemistry," for example, it is also stated that
arseniureted hydrogen is formed by the _fermentation_ of the starch-paste
employed for fastening the paper to the walls. It is perfectly obvious
that the fermentation of the starch-paste must cease after a time, and
therefore the poisonous effects of the paper must likewise cease if its
injurious effects are caused by the fermentation. I do not think that
arseniureted hydrogen could be formed under the _conditions_, for the
oxygen compound of arsenic is in a state of combination, and the compound
is in a dry solid state and not in solution and the affinities of the two
elements--arsenic and hydrogen--for each other are so exceedingly weak
that they cannot be made to unite directly except they are both set free
at the same moment in presence of each other. Further, for the formation
of this hydrogen compound by the fermentation of the starch, or by the
growth of minute fungi, the _entire_ compound must be broken up, and
therefore the pigment would become discolored; but aceto-arsenite of
copper

(3CuAs_{2}O_{4}+Cu(C_{2}H_{3}O_{2})_{2})

is a very stable compound, not readily undergoing decomposition, and is
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 manufactu