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SULPHUR DIOXIDE 743
Fatal Dose and Fatal Period.—A concentration of 0.02 per cent of hydrogen sulphide
in the air is sufficient to produce local irritation in man; 0.05 per cent gives rise to
alarming symptoms, if breathed for half an hour, while 0.07 per cent is dangerous • 0.18
per cent proves fatal immediately.
Chronic Poisoning.—This occurs in workmen who are exposed to the constant in-
halation of this gas for a prolonged period. According to Haggard is the prolonged
inhalation of a concentration of the gas even as low as 0.01 per cent is sufficient to induce
symptoms of chronic poisoning.
Symptoms.—These are conjunctivitis, headache, gastric disturbances, anaemia, and
furunculosis. Nervous disturbances are also present.
Treatment.—Fresh air, inhalation of oxygen, prompt artificial respiration and
warmth to the extremities. Give intravenously respiratory stimulants, such as coramine
(1 to 2 cc. of a 25 per cent solution), rnetrazol (1£ to 6 grains) or caffeine with sodium
benzoate (7J to 15 grains).
Post-mortem Appearances.—Putrefaction sets in much more rapidly. An offensive
smell is noticed on opening the body. The blood is liquid and dark-brown in colour
from the conversion of hemoglobin into sulphmethaemoglobin, which is characterized
by an absorption spectrum of two bands, consisting of one band in the red between C
and D, and a fainter band between D and E. The lungs are congested and cedematous.
The other organs are dark and congested.
Tests.—1. Hydrogen sulphide is recognized by its offensive smell, which is percep-
tible when one part is present in 10,000 of air.
2. A piece of white filter paper moistened with lead acetate or carbonate turns
black on bringing it in contact with the stomach or other organs containing -the gas.
NITROGEN MONOXIDE (NITROUS OXIDE OR LAUGHING GAS), N2O
This is a colourless gas, obtained by heating ammonium nitrate, and has a charac-
teristic odour and faintly sweetish taste. It does not break up and give oxygen to the
body. It is a pharmacopoeia! preparation, called Nitrogenii monoxidum.
Symptoms.—When inhaled mixed with 20 per cent of oxygen, it produces after a
few seconds a condition of hysterical excitement often accompanied by noisy laughter and
gas intoxication; hence it is known as laughing gas. When pushed beyond this hysteri-
cal stage, it causes anaesthesia, and is used in minor surgery, especially dentistry. Death
occurs usually within a few minutes of inhalation, but it is very rare. Death occurred
in two cases in 60 and 74 hours from the commencement of its inhalation.17 A case of
accidental death from self-administration of nitrous oxide as an anaesthetic is recorded,
wherein a dentist was found dead in his operating chair with the mask applied to his
face,18 By taking occasional whiffs of the gas for a prolonged period one gets addicted
to it and the habit thus formed is difficult to break.
When inhaled in the pure state, it at first causes the abovementioned symptoms
followed immediately by unconsciousness, cyanosis, cold, clammy sweats, dyspnoeic and
stertorous breathing, and death from respiratory paralysis. The heart may continue to
beat for some time after the stoppage of respiration.
Treatment.—This consists in the inhalation of oxygen and carbon dioxide, artificial
respiration and stimulants.
Post-mortem Appearances.—There may be degenerative changes in the cortex of
the brain and in the parenchyma of the basal ganglia. The blood is dark in colour.
Tests.—The gas supports combustion, but not life. It dissolves in alcohol.
Case.—A 58-year-old man died in about eight and a half hours from respiratory
failure caused by anoxaemia due to nitrous oxide administered inadvertently for oxygen
in the course of an anaesthetic given for an operation for a perforated peptic ulcer.—
Lancet, Dec. 24, 1949, p. 1205.
SULPHUR DIOXIDE (SULPHUROUS ACID GAS OR
SULPHUROUS ANHYDRIDE), SO*
This is formed by burning sulphur or certain metallic sulphides, such as iron
pyrites, in air or oxygen, and is a bi-product in the manufacture of sulphuric acid. It
is met with in the gaseous emanations from volcanoes. It is present in a noticeable
amount in the air of towns, being derived from the combustion of the sulphur com-
pounds present in coal.
16, Jour, of Industrial Hygiene, March 1925, p. 113.
17, K. Lowenberg, R. Waggoner and T. Zainden, Ann. Surg.t November 1936, p. 801;
Lancet, Jan. 16, 1937, p. 158.
18, Holmes and Visick, Lancet, Dec. 4, 1920, p. 1167. ,