it on evaporation in a crystalline form.

_General Reactions for Alkaloids._--(1) Wagner's reagent (iodine
dissolved in a solution of potassium iodide) yields a reddish-brown
precipitate; (2) Mayer's reagent (potassio-mercuric iodide) gives a
yellowish-white precipitate; (3) phospho-molybdic acid gives a yellow
precipitate; (4) platinic chloride, a brown precipitate; (5) tannic
acid, etc.

In order to isolate an inorganic substance from organic matter,
Fresenius's method is adopted. Boil the finely divided substance with
about one-eighth its bulk of pure hydrochloric acid; add from time to
time potassic chlorate until the solids are reduced to a straw-yellow
fluid. Treat this with excess of bisulphate of sodium, then saturate
with sulphuretted hydrogen until metals are thrown down as sulphides.
These may be collected and tested. From the acid solution, hydrogen
sulphide precipitates copper, lead, and mercury, _dark_; arsenic,
antimony, and tin, _yellowish_. If no precipitate, add ammonia and
ammonium sulphide, iron, _black_, zinc, _white_, chromium, _green_,
manganese, _pink_. The residue of the material after digestion with
hydrochloric acid and potassium chlorate may have to be examined for
silver, lead, and barium.

For the detection of minute quantities, the microscope must be used, and
Guy's and Helwig's method of sublimation will be found advantageous.
Crystalline poisons may be recognized by their characteristic forms.

IX.--THE MINERAL ACIDS

These are sulphuric, nitric, and hydrochloric acids.

_Symptoms of Poisoning by the Mineral Acids._--Acid taste in the mouth,
with violent burning pain extending into the oesophagus and stomach, and
commencing immediately on the poison being swallowed; eructations,
constant retching, and vomiting of brown, black, or yellow matter
containing blood, coagulated mucus, epithelium, or portions of the
lining membrane of the gullet and stomach. The vomited matters are
strongly acid in reaction, and stain articles of clothing on which they
may fall. There is intense thirst and constipation, with scanty or
suppressed urine, tenesmus, and small and frequent pulse; the lips,
tongue, and inside of the mouth, are shrivelled and corroded. Exhaustion
succeeds, and the patient dies either collapsed, convulsed, or
suffocated, the intellect remaining clear to the last. After recovering
from the acute form of poisoning, the patient may ultimately die from
starvation, due to st