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Arsenic And Its Preparations





=Arsenic= is the most important of all the metallic poisons. It is much
used in medicine and the arts. It occurs as metallic arsenic, which is
of a steel-grey colour, brittle, and gives off a garlic-like odour when
heated; as arsenious acid; in the form of two sulphides--the red
sulphide, or realgar, and the yellow sulphide, or orpiment; and as
arsenite of copper, or Scheele's green. It also exists as an impurity in
the ores of several metals--iron, copper, silver, tin, zinc, nickel, and
cobalt. Sulphuric acid is frequently impregnated with arsenic from the
iron pyrites used in preparing the acid. It is a constituent of many rat
pastes, vermin or weed killers, complexion powders, sheep dips, etc.

=Arsenious Acid= (White Arsenic, Trioxide of Arsenic).--Colourless,
odourless, and almost tasteless. It occurs in commerce as a white powder
or in a solid cake, which is at first translucent, but afterwards
becomes opaque. Slightly soluble in cold water; 1 ounce of water
dissolves about 1/2 grain of arsenic. Fowler's solution is the
best-known medicinal preparation of arsenic, and contains 1 grain of
arsenious anhydride in 110 minims.

Symptoms.--Commence in from half to one hour. Faintness, nausea,
incessant vomiting, epigastric pain, headache, diarrhoea, tightness and
heat of throat and fauces, thirst, catching in the breath, restlessness,
debility, cramp in the legs, and convulsive twitchings. The skin becomes
cold and clammy. In some cases the symptoms are those of collapse, with
but little pain, vomiting, or diarrhoea. In others the patient falls
into a deep sleep, while in the fourth class the symptoms resemble
closely those of English cholera. The vomited matters are often blue
from indigo, or black from soot, or greenish from bile, mixed with the
poison. Should the patient survive some days, no trace of arsenic may be
found in the body, as the poison is rapidly eliminated by the kidneys.
In all suspected cases the urine should be examined.

The symptoms of chronic poisoning by arsenic are loss of appetite,
silvery tongue, thirst, nausea, colicky pains, diarrhoea, headache,
languor, sleeplessness, cutaneous eruptions, soreness of the edges of
the eyelids, emaciation, falling out of the hair, cough, hæmoptysis,
anæmia, great tenderness on pressure over muscles of legs and arms, due
to peripheral neuritis, and convulsions.

Pigmentation is common; the face becomes dusky red, the rest of the body
a dark brown shade. This darkening is most marked in situations normally
pigmented and in parts exposed to pressure of the clothes, such as the
neck, axilla, and inner aspect of the arms, the extensor aspects being
less marked than the flexor. The pigmentation resembles the bronzing of
Addison's disease, but there are no patches on the mucous membranes, and
the normal rosy tint of the lips is not altered. The skin over the feet
may show marked hyperkeratosis.

The nervous system is notably affected. The sensory symptoms appear
first: numbness and tingling of the hands and feet, pain in the soles of
the feet on walking, pain on moving the joints, and erythromelalgia.
Then come the motor symptoms, with drop-wrist and drop-foot. The patient
suffers severely from neuritis, and there may be early loss of patellar
reflex. The nervous symptoms come on later than the cutaneous
manifestations.

Post-Mortem Appearances.--Signs of acute inflammation of stomach,
duodenum, small intestines, colon, and rectum. Stomach may contain dark
grumous fluid, and its mucous coat presents the appearance of crimson
velvet. Ulceration is rare, and cases of perforation still less common,
the patient dying before it occurs. If life has been preserved for some
days, there is extensive fatty degeneration of the organs. There may be
entire absence of post-mortem signs. Putrefaction of the body is
retarded by arsenic.

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
characters: In the centre a deposit of metallic arsenic, round this a
mixture of metallic arsenic and arsenious acid, and outside this another
ring of arsenious acid in octahedral crystals. The deposit is dissolved
by a solution of chloride of lime, turned yellow by sulphide of ammonium
after evaporation; on the addition of strong nitric acid, evaporated and
neutralized with ammonia and nitrate of silver added, a brick-red colour
is produced--arseniate of silver.

Reinsch's Process.--Boil distilled water with one-sixth or one-eighth
of hydrochloric acid, and introduce a slip of bright copper. If, after a
quarter of an hour's boiling, there is no stain on the copper, add the
suspected liquid. If arsenic be present, it will form an iron-grey
deposit. If this foil be dried, cut up, put in a reduction-tube, and
heated, crystals of arsenious trioxide will be deposited on the cold
part of the tube.

These tests are difficult to apply, but as arsenic is a ubiquitous
poison, and as there are many sources of fallacy, it would be well, when
possible, to obtain the services of an expert.

Biological Test.--Put the substance to be tested into a flask with
some small pieces of bread, sterilize for half an hour at 120° C. When
cold, inoculate with a culture of Penicillium brevicaule, and keep at
a temperature of 37° C. If arsenic is present, a garlic-like odour is
noticed in twenty four hours, due to arseniuretted hydrogen or an
organic combination of arsenic. This test is delicate, and will detect
1/1000 of a milligramme, but it is not quantitative.

=Other Preparations of Arsenic.=--These are arsenite of potash (Fowler's
solution), cacodylate of sodium, and arsenite of copper (Scheele's
green), the last frequently used for colouring dresses and wall-papers.
Persons using these preparations may suffer from catarrhal symptoms,
rashes on the neck, ears, and face, thirst, nausea, pain in stomach,
vomiting, headache, perhaps peripheral neuritis and loss of patellar
reflex. The cacodylates, although formerly employed in the treatment of
phthisis, should be used with the utmost caution. The arsenites give the
reactions of arsenious acid.

Arsenic is eliminated not only by the kidneys and bowels, but by the
skin, and in women by the menses. It may be detected in the sweat, the
saliva, the bronchial secretion, and, during lactation, in the milk.

The sale of arsenic and its preparations to the public is properly
hedged round with restrictions of all kinds. It is included in Part I.
of the Poisons and Pharmacy Act (8 Edward VII., c. 55). No arsenic may
be sold to a person under age, nor may it be sold unless mixed with soot
or indigo in the proportion of 1 ounce of soot or 1/2 ounce of indigo at
the least to every pound of arsenic.

=Arseniuretted Hydrogen= (arsine, AsH{3}) is an extremely poisonous
gas, and is evolved in various chemical and manufacturing processes.
When damp, Ferro-silicon evolves AsH{3} and PH{3}, both very lethal
gases. Ferrochrome is used in making steel, and it also evolves
PH{3}, and in such extreme dilution as 0.02 per cent. may cause death.





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Previous: Phosphorus



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