r survival for several days. In all cases every
organ should be examined. Vomited matters and contents of stomach should
not be mixed, but each _separately_ examined. This rule holds good for
all poisons. On _cloth_ the stain may be cut out, boiled in water, the
solution filtered, and tested with blue litmus and other tests.

_Post-Mortem Appearances._--Where the acid has come in contact with the
mucous membranes there are dark brown or black patches. The stomach is
greatly contracted, the summits of the mucous membrane ridges being
charred and the furrows greatly inflamed; the contents are black or
brown.

_Tests._--Concentrated acid chars organic matter; evolves heat when
added to water, and sulphurous fumes when boiled with chips of wood,
copper cuttings, or mercury. Dilute acid chars paper when the paper is
heated; gives a white precipitate with nitrate or chloride of barium,
and is entirely volatilized by heat. Dilute solutions give a white
precipitate with barium nitrate, insoluble in hydrochloric acid even on
boiling.

_Fatal Dose._--In an adult, 1 drachm.

_Fatal Period._--Shortest, three-quarters of an hour; average period
from onset of primary effects, eighteen to twenty-four hours.

XI.--NITRIC ACID

=Nitric Acid=, or aqua fortis, is less frequently used as a poison than
sulphuric acid. The fumes from nitric acid have caused death from
pneumonia in ten or twelve hours.

_Method of Extraction from the Stomach._--The same as for sulphuric
acid. In beer, etc., the mixture may be neutralized with carbonate of
potassium, dialyzed, the fluid concentrated and allowed to crystallize,
when crystals of nitrate of potassium may be recognized.

_Post-Mortem Appearance._--The mucous membranes are rendered yellow or
greenish if bile be present; they are also thickened and hardened.

_Tests._--Concentrated acid gives off irritating orange-coloured fumes
of nitric acid gas. When poured on copper, it gives off red fumes and
leaves a green solution of nitrate of copper. It gives a red colour with
brucine, turns the green sulphate of iron black, and with hydrochloric
acid dissolves gold. A delicate test for the acid, free or in
combination, is to dissolve in the suspected fluid some crystals of
ferrous sulphate, and then to gently pour down the test-tube some strong
sulphuric acid. Where the two liquids meet, if nitric acid be present, a
reddish-brown ring will be formed. It turns the skin bright yellow, and