be without interest.

In the paragraph referred to, it is stated that the poisonous effect of
this pigment cannot be _entirely_ due to its mere mechanical detachment
from the paper. This writer therefore attributes the poisonous effects to
the formation of the hydrogen compound of arsenic, viz., arseniureted
hydrogen (AsH_{3}); the hydrogen, for the formation 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