_Treatment._--The stomach-pump, emetics, then milk, milk and eggs, oil
and lime-water. Inflammatory symptoms, collapse, coma, etc., must be
treated on ordinary principles. As an antidote, the best when the poison
is in solution is the hydrated sesquioxide of iron, formed by
precipitating tinctura ferri perchloridi with excess of ammonia, or
carbonate of soda. This is filtered off through muslin and given in
tablespoonful doses. It forms ferric arsenate, which is sparingly
soluble. Colloidal iron hydroxide may be used instead. Dialyzed iron in
large quantities is efficacious.

_Fatal Dose (Smallest)._--Two grains. Exceptionally, recovery from very
large doses if rejected by vomiting.

_Fatal Period (Shortest)._--Twenty minutes. Exceptionally, death as late
as the sixteenth day. The effects of arsenic are modified by tolerance,
some persons being able to take considerable quantities. The peasants of
Styria are in the habit of eating it.

_Method of Extraction from the Stomach._--The coats of the stomach
should be examined with a lens for any white particles. These, if
present, may be collected, mixed with a little charcoal in a test-tube,
and heated. If arsenic is present, a metallic ring will be formed in the
cooler parts of the tube. If this ring be also heated, octahedral
crystals of arsenic will be deposited farther up the tube, and are
easily recognized by the microscope. The contents of the stomach, or the
solid organs minced up, should be boiled with pure hydrochloric acid and
water, then filtered. The filtrate can then be subjected to Marsh's or
Reinsch's process.

_Tests._--In _solution_, arsenic may be detected by the liquid tests.
(1) Ammonio-nitrate of silver gives a yellow precipitate (arsenite of
silver). (2) Ammonio-sulphate of copper gives a green precipitate
(Scheele's green). (3) Sulphuretted hydrogen water gives a yellow
precipitate.

_Marsh's Process._--Put pure distilled water into a Marsh's apparatus
with metallic zinc and sulphuric acid. Hydrogen is set free, and should
be tested by lighting the issuing gas and depressing over it a piece of
white porcelain. If no mark appears, the reagents are pure, and the
suspected liquid may now be added. The hydrogen decomposes arsenious
acid, and forms arseniuretted hydrogen. The gas carried off by a fine
tube is again ignited. A piece of glass or porcelain held to the flame
will have, if arsenic be present, a deposit on it having the following
charac