MERCURY	529
Chronic Poisoning.—This form, of poisoning occurs among those who are
exposed to the vapours of mercury in factories where mercury and its salts
are largely used. It also occurs among those who have taken internally for
a prolonged period excessive doses of mercury compounds, or used the
mercurial ointment in the form of an external application.
Symptoms.—These are nausea, digestive disturbances, colicky pain,
vomiting and diarrhoea. Ptyalism or salivation is a constant symptom which
is accompanied by foul breath, swollen and painful salivary glands and
inflamed and ulcerated gums, which usually present a blue line at their,
junction with the teeth. Later, the teeth become loo'se and carious, necrosis
of the jaw occurs, and the patient suffers from a condition known as ergthjgPij
which is characterized by shyness, timidity, irritability, loss of c<52S[ence,
mental depression, loss ot memory and insomnia. Sometimes, the patient is
affected by mental disturbances,, hallucinations and delusions, which may
result in insanity.
The skin eruptions of an erythematous, eczematous or pustular type may
be noticed. The nervous symptoms, known as mercurial tremors, super-
vene, these are considerably coarser than in thyrotoxicosis. These first of
all affect the muscles of the tongue, producing stammering and hesitation of
speech, and then affect the muscles of the face; these latter extend to the
muscles of the arms and legs. They are excited by voluntary movements,
and are absent during sleep. The tremors are followed by paralysis of the
limbs. The patient complains of cough with, bloody expectoration, suffers
from general wasting, anaemia and chronic nephritis, and dies from
exhaustion.
Treatment.—The patient should be removed from the surroundings
where he was exposed to the poison. He should be directed to drink milk
freely and to gargle his mouth with potassium, chlorate or borax, to keep his
bowels open by saline purgatives, and to take warm baths to promote the
action of the skin. Intravenous injections of sodium thiosulphate in doses
of 0.45 to 0.6 gramme in 5 cc. of water on alternate days are considered
efficacious for the treatment of salivation.^61
It is advisable to give potassium iodide in small doses, so that the poison
may be converted into mercuric iodide, which is soluble in excess of the
potassium salt. Massage and electricity should be advised for paralysis.
Narcotics should be given for severe tremors.
Post-mortem Appearances.—The heart and liver may show fatty dege-
neration. The kidneys show parenchymatous nephritis.
Chemical Tests for Mercuric Salts.—1. Hydrochloric acid and sul-
phuretted hydrogen give a yellow precipitate which changes to orange
brown and lastly black, insoluble in alkalis or dilute acids.
 2.	Caustic potash gives a yellow or orange precipitate.
 3.	Potassium iodide gives a scarlet precipitate, soluble in excess.
 4.	Stannous chloride gives a white precipitate, changing to black.
 5.	If a piece of a bright wire of copper be introduced into the solution
acidulated with a few drops of hydrochloric acid, a silver coating of mercury
will be formed on the wire.
Chemical Tests for Mercurous Salts.—1. Hydrochloric acid -gives a
white precipitate, which is insoluble in acids and is blackened by attrmonia.
 2.	Potassium iodide gives a yellowish-green precipitate, which becomes
grey or greyish-black if the reagent is added in excess and then heated.
 3.	Caustic potash yields a black precipitate, insoluble in excess.
61.   H. C. Semon, Brit. Med. Jour., April 12, 1944, p. 662.
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