I.--Carbon Monoxide.
§ 37. Carbon monoxide, CO, is a colourless, odourless gas of 0·96709 sp.
gravity. A litre weighs 1·25133 grm. It is practically insoluble in
water. It unites with many metals, forming gaseous or volatile
compounds, _e.g._, nickel carbon oxide, Ni(CO)₄, is a fluid volatilising
at 40°. These compounds have, so far as is known, the same effects as
CO.
Whenever carbon is burned with an insufficient supply of air, CO in a
certain quantity is produced. It is always present in ordinary domestic
products of combustion, and must be exhaled from the various chimneys of
a large city in considerable volumes. A “smoky” chimney or a defective
flue will therefore introduce carbon monoxide into living-rooms. The
vapour from burning coke or burning charcoal is rich in carbon monoxide.
It is always a constituent of coal gas, in England the carbon monoxide
in coal gas amounting to about 8 per cent. Poisoning by coal gas is
practically poisoning by carbon monoxide. Carbon monoxide is also the
chief constituent in water gas.
Carbon monoxide poisoning occurs far more frequently in France and
Germany than in England; in those countries the vapour evolved from
burning charcoal is a favourite method of suicide, on account of the
supposed painlessness of the death. It has also occasionally been used
as an instrument of murder. In this country carbon monoxide poisoning
mainly takes place accidentally as the effect of breathing coal gas;
possibly it is the secret and undetected cause of ill health where
chimneys “smoke”; and it may have something to do with the sore throats
and debility so often noticed when persons breathe for long periods air
contaminated by small leakages of coal gas.
The large gas-burners (geysers) emit in burning under certain conditions
much carbon monoxide. It has been proved by Gréhant[56] that a bunsen
burner “lit below” also evolves large quantities of the same poisonous
gas.
[56] _Compt. Rend. Soc. de Biol._, ix. 779-780.
§ 38. =Symptoms.=--Nearly all the experience with regard to the symptoms
produced by carbon monoxide is derived from breathing not the pure gas,
but the gas diluted by air, by hydrogen or by carburetted hydrogen, as
in coal gas, or mixed with large quantities of carbon dioxide. Two
assistants of Christison breathed the pure gas: the one took from two to
three inhalations; he immediately became giddy, shivered, had headache
and then became unconscious. The second took a bigger dose, for, after
emptying his lungs as much as possible, he took from three to four
inhalations; he fell back paralysed, became unconscious and remained
half-an-hour insensible and had the appearance of death, the pulse being
almost extinguished. He was treated with inhalations of oxygen, but he
remained for the rest of the day extremely ill; he had convulsive
muscular movements, stupor, headache, and quick irregular pulse; on this
passing away he still suffered from nausea, giddiness, alternate feeling
of heat and chilliness, with some fever, and in the night had a restless
kind of sleep. The chemist Chenot was accidentally poisoned by the pure
gas, and is stated to have fell as if struck by lightning after a single
inspiration, and remained for a quarter of an hour unconscious. Other
recorded cases have shown very similar symptoms.
The pulse is at the onset large, full and frequent; it afterwards
becomes small, slow and irregular. The temperature sinks from 1° to 3°
C. The respiration at first slow, later becomes rattling. As vomiting
occurs often when the sufferer is insensible, the vomited matters have
been drawn by inspiration into the trachea and even into the bronchi, so
that death takes place by suffocation.
The fatal coma may last even when the person has been removed from the
gas from hours to days. Coma for three, four and five days from carbon
monoxide has been frequently observed. The longest case on record is
that of a person who was comatose for eight days, and died on the
twelfth day after the fatal inhalation. Consciousness in this case
returned, but the patient again fell into stupor and died.
The slighter kinds of poisoning by carbon monoxide, as in the
Staffordshire case recorded by Dr. Reid, in which for a long time a much
diluted gas has been breathed, produce pronounced headache and a general
feeling of ill health and _malaise_, deepening, it may be, into a fatal
slumber, unless the person is removed from the deadly atmosphere. To the
headache generally succeeds nausea, a feeling of oppression in the
temples, a noise in the ears, feebleness, anxiety and a dazed condition
deepening into coma. It is probably true that charcoal vapour is
comparatively painless, for when larger amounts of the gas are breathed
the insensibility comes on rapidly and the faces of those who have
succumbed as a rule are placid. Vomiting, without being constant, is a
frequent symptom, and in fatal cases the fæces and urine are passed
involuntarily. There are occasional deviations from this picture;
tetanic strychnine-like convulsions have been noticed and a condition of
excitement in the non-fatal cases as if from alcohol; in still rarer
cases temporary mania has been produced.
In non-fatal but moderately severe cases of poisoning sequelæ follow,
which in some respects imitate the sequelæ seen on recovery from the
infectious fevers. A weakness of the understanding, incapacity for
rational and connected thought, and even insanity have been noticed.
There is a special liability to local inflammations, which may pass into
gangrene. Various paralyses have been observed. Eruptions of the skin,
such as herpes, pemphigus and others. Sugar in the urine is an almost
constant concomitant of carbon monoxide poisoning.
§ 39. The poisonous action of carbon monoxide is, without doubt, due to
the fact that it is readily absorbed by the blood, entering into a
definite chemical compound with the hæmoglobin; this combination is more
stable than the similar compound with oxygen gas, and is therefore slow
in elimination.
Hence the blood of an animal remaining in an atmosphere containing
carbon monoxide is continually getting poorer in oxygen, richer in
carbon monoxide. Gréhant has shown that if an animal breathes for one
hour a mixture of 0·5 carbon monoxide to 1000 oxygen, the blood contains
at the end of that time one-third less oxygen than normal, and contains
152 times more carbon monoxide than in the mixture. An atmosphere of 10
per cent. carbon monoxide changes the blood so quickly, that after from
10 to 25 seconds the blood contains 4 per cent. of carbon monoxide, and
after from 75 to 90 seconds 18·4 per cent. Breathing even for half an
hour an atmosphere containing from 0·07 to 0·12 per cent. carbon
monoxide renders a fourth part of the red corpuscles of the blood
incapable of uniting with oxygen.
The blood is, however, never saturated with carbon monoxide, for the
animal dies long before this takes place.
The characteristics of the blood and its spectroscopic appearances are
described at p. 58.
Besides the action on the blood there is an action on the nervous
system. Kobert,[57] in relation to this subject, says:--“That CO has a
direct action on the nervous system is shown in a marked manner when an
atmosphere of oxygen, with at least 20 per cent. carbon oxide, is
breathed; for in the first minute there is acute cramp or total
paralysis of the limbs, when the blood in no way attains the saturation
sufficiently great to account for such symptoms. Geppert has, through a
special research, shown that an animal suffocated by withdrawal of
oxygen, increases the number and depth of the respirations; but when the
animal is submitted to CO, in which case there is quite as much a
withdrawal of oxygen as in the former case, yet the animal is not in a
condition to strengthen its respiratory movements; Geppert hence rightly
concludes that CO must have a primary specific injurious action on the
nerve centres. I (Kobert) am inclined to go a step further, and, on the
ground of unpublished researches, to maintain that CO not only affects
injuriously the ganglion cells of the brain, but also the peripheral
nerves (_e.g._, the phrenic), as well as divers other tissues, as
muscles and glands, and that it causes so rapidly such a high degree of
degeneration as not to be explained through simple slow suffocation;
even gangrene may be caused.”
[57] _Lehrbuch der Intoxicationen_, 526.
It is this rapid degeneration which is the cause of the enormous
increase of the products of the decomposition of albumin, found
experimentally in animals.
§ 40. =Post-mortem Appearances.=--The face, neck, chest, abdomen are
frequently covered with patches of irregular form and of clear rose-red
or bluish-red colour; these patches are not noticed on the back, and
thus do not depend upon the gravitation of the blood to the lower or
most dependent part of the body; similar red patches have been noticed
in poisoning by prussic acid; the cause of this phenomenon is ascribed
to the paralysis of the small arteries of the skin, which, therefore,
become injected with the changed blood. The blood throughout is
generally fluid, and of a fine peculiar red colour, with a bluish tinge.
The face is mostly calm, pale, and there is seldom any foam about the
lips. Putrefaction is mostly remarkably retarded. There is nearly always
a congestion of some of the internal organs; sometimes, and indeed
usually, the membranes of the brain are strongly injected; sometimes the
congestion is mainly in the lungs, which may be œdematous with effusion;
and in a third class of cases the congestion is most marked in the
abdominal cavity.
The right heart is commonly filled with blood, and the left side
contains only a little blood.
Poisoning by a small dose of carbon monoxide may produce but few
striking changes, and then it is only by a careful examination of the
blood that evidence of the real nature of the case will be obtained.
§ 41. =Mass poisonings by Carbon Monoxide.=--An interesting series of
cases of poisoning by water gas occurred at Leeds in 1889, and have been
recorded by Dr. Thos. Stevenson.[58]
[58] _Guy’s Hospital Reports_, 1889.
Water gas is made by placing coke in a vertical cylinder and heating the
coke to a red heat. Through the red-hot coke, air is forced up from
below for ten minutes; then the air is shut off and steam passes from
above downwards for four minutes; the gas passes through a scrubber, and
then through a ferric oxide purifier to remove SH₂. It contains about 50
per cent. of hydrogen and 40 per cent. of carbon monoxide, that is,
about five times more carbon monoxide than coal gas.
On November 20, 1889, two men, R. French and H. Fenwick, both
intemperate men, occupied a cabin at the Leeds Forge Works; the cabin
was 540 c. feet in capacity, and was lighted by two burners, each
burning 5·5 c. feet of water gas per hour; the cabin was warmed by a
cooking stove, also burning water gas, the products of combustion
escaping into the cabin. Both men went into the cabin after breakfast
(8.30 A.M.). French was seen often going to and fro, and Fenwick was
seen outside at 10.30 A.M. At 11.30 the foreman accompanied French to
the cabin, and found Fenwick asleep, as he thought. At 12.30 P.M.
French’s son took the men their dinner, which was afterwards found
uneaten. At that time French also appeared to be asleep; he was shaken
by his son, upon which he nodded to his son to leave. The door of the
cabin appears to have been shut, and all through the morning the lights
kept burning; no smell was experienced. At 2.30 P.M. both the men were
discovered dead. It was subsequently found that the stove was unlighted,
and the water gas supply turned on.
What attracted most attention to this case was the strange incident at
the _post-mortem_ examination. The autopsies were begun two days after
the death, November 22, in a room of 39,000 c. feet capacity. There were
present Mr. T. Scattergood (senior), Mr. Arthur Scattergood (junior),
Mr. Hargreaves, three local surgeons, Messrs. Brown, Loe and Jessop, and
two assistants, Pugh and Spray. Arthur Scattergood first fainted, Mr.
Scattergood, senior, also had some peculiar sensations, viz., tingling
in the head and slight giddiness; then Mr. Pugh became faint and
staggered; and Mr. Loe, Mr. Brown, and Mr. Spray all complained.
These symptoms were not produced, as was at first thought, by some
volatile gas or vapour emanating from the bodies of the poisoned men,
but, as subsequently discovered, admitted of a very simple explanation;
eight burners in the room were turned partly on and not lighted, and
each of the eight burners poured water gas into the room.
In 1891 occurred some cases of poisoning[59] by CO which are probably
unique. The cases in question happened in January in a family at
Darlaston. The first sign of anything unusual having happened to the
family most affected was the fact that up to 9 A.M., Sunday morning,
January 18, none of the family had been seen about. The house was broken
into by the neighbours; and the father, mother, and three children were
found in bed apparently asleep, and all efforts to rouse them utterly
failed. The medical men summoned arrived about 10 A.M. and found the
father and mother in a state of complete unconsciousness, and two of the
children, aged 11 and 14 years, suffering from pain and sickness and
diarrhœa; the third child had by this time been removed to a
neighbouring cottage.
[59] “Notes on cases of poisoning by the inhalation of carbon monoxide,”
by Dr. George Reid, Medical Officer of Health, County of Stafford.
_Public Health_, vol. iii. 364.
Dr. Partridge, who was in attendance, remained with the patients three
hours, when he also began to suffer from headache; while others, who
remained in the house longer, suffered more severely and complained of
an indefinite feeling of exhaustion. These symptoms pointed to some
exciting cause associated with the surroundings of the cottage;
consequently, in the afternoon the two children were removed to another
cottage, and later on the father and mother also. All the patients, with
the exception of the mother, who was still four days afterwards
suffering from the effects of an acute attack, had completely recovered.
The opinion that the illness was owing to some local cause was
subsequently strengthened by the fact that two canaries and a cat had
died in the night in the kitchen of the cottage; the former in a cage
and the latter in a cupboard, the door of which was open. Also in the
same house on the opposite side of the road, the occupants of which had
for some time suffered from headache and depression, two birds were
found dead in their cage in the kitchen. It is important to notice that
all these animals died in the respective kitchens of the cottages, and,
therefore, on the ground floor, while the families occupied the first
floor.
The father stated that for a fortnight or three weeks previous to the
serious illness, he and the whole family had complained of severe
frontal headache and a feeling of general depression. This feeling was
continuous day and night in the case of the rest of the family, but in
his case, during the day, after leaving the house for his work, it
gradually passed off, to return again during the night. The headaches
were so intense that the whole family regularly applied vinegar rags to
their heads, on going to bed each night during this period, for about
three weeks. About two o’clock on Sunday morning the headaches became so
severe that the mother got out of bed and renewed the application of
vinegar and water all round, after which they all fell asleep, and, so
far as the father and mother were concerned, remained completely
unconscious until Monday morning.
A man who occupied the house opposite the house tenanted by the
last-mentioned family informed the narrator (Dr. Reid) that on Sunday
morning the family, consisting of four, were taken seriously ill with a
feeling of sickness and depression accompanied by headache; and he also
stated that for some time they had smelt what he termed a “fire stink”
issuing from the cellar.
The cottage in which the family lived that had suffered so severely was
situated about 20 or 30 yards from the shaft of a disused coal mine, and
was the end house of a row of cottages. It had a cellar opening into the
outer air, but this opening was usually covered over by means of a piece
of wood. The adjoining house to this, the occupants of which had for
some time suffered from headache, although to a less extent, had a
cellar with a similar opening, but supplied with an ill-fitting cover.
The house on the opposite side of the road, in which the two birds were
found dead, had a cellar opening both at the front and the back; but
both these openings, until a little before the occurrence detailed, had
been kept closed. The cellars in all cases communicated with the houses
by means of doors opening into the kitchens. According to the general
account of the occupants, the cellars had smelled of “fire stink,”
which, in their opinion, proceeded from the adjoining mine.
The shaft of the disused mine communicated with a mine in working order,
and, to encourage the ventilation in this mine, a furnace had for some
weeks been lit and suspended in the shaft. This furnace had set fire to
the coal in the disused mine and smoke had been issuing from the shaft
for four weeks previously. Two days previous to the inquiry the opening
of the shaft had been closed over with a view to extinguish the fire.
Dr. Reid considered, from the symptoms and all the circumstances of the
case, that the illness was due to carbon monoxide gas penetrating into
the cellars from the mine, and from thence to the living- and
sleeping-rooms. A sample of the air yielded 0·015 per cent. of carbon
monoxide, although the sample had been taken after the cellar windows
had been open for twenty-four hours.
§ 42. =Detection of Carbon Monoxide.=--It may often be necessary to
detect carbon monoxide in air and to estimate its amount. The detection
in air, if the carbon monoxide is in any quantity, is easy enough; but
traces of carbon monoxide are difficult. Where amounts of carbon
monoxide in air from half a per cent. upwards are reasonably presumed to
exist, the air is measured in a gas measuring apparatus and passed into
an absorption pipette charged with alkaline pyrogallic acid, and when
all the oxygen has been abstracted, then the residual nitrogen and gases
are submitted to an ammoniacal solution of cuprous chloride.
The solution of cuprous chloride is prepared by dissolving 10·3 grms. of
copper oxide in 150 c.c. of strong hydrochloric acid and filling the
flask with copper turnings; the copper reduces the cupric chloride to
cuprous chloride; the end of the reduction is known by the solution
becoming colourless. The colourless acid solution is poured into some
1500 c.c. of water, and the cuprous chloride settles to the bottom as a
precipitate. The supernatant fluid is poured off as completely as
possible and the precipitate washed into a quarter litre flask, with 100
to 150 c.c. of distilled water and ammonia led into the solution until
it becomes of a pale blue colour. The solution is made up to 200 c.c. so
as to contain about 7·3 grms. per cent. of cuprous chloride.
Such a solution is an absorbent of carbon monoxide; it also absorbs
ethylene and acetylene.
A solution of cuprous chloride which has absorbed CO gives it up on
being treated with potassic bichromate and acid. It has been proposed by
Wanklyn to deprive large quantities of air of oxygen, then to absorb any
carbon monoxide present with cuprous chloride, and, lastly, to free the
cuprous chloride from the last gas by treatment with acid bichromate, so
as to be able to study the properties of a small quantity of pure gas.
By far the most reliable method to detect small quantities of carbon
monoxide is, however, as proposed by Hempel, to absorb it in the lungs
of a living animal.
A mouse is placed between two funnels joined together at their mouths by
a band of thin rubber; one of the ends of the double funnel is connected
with an aspirator, and the air thus sucked through, say for half an hour
or more; the mouse is then killed by drowning, and a control mouse,
which has not been exposed to a CO atmosphere, is also drowned; the
bodies of both mice are cut in two in the region of the heart, and the
blood collected. Each sample of blood is diluted in the same proportion
and spectroscopically examined in the manner detailed at p. 58.
Winkler found that, when large volumes of gas were used (at least 10
litres), 0·05 per cent. of carbon monoxide could be readily detected.
II.--Chlorine.
§ 43. Chlorine is a yellow-green gas, which may, by cold and pressure,
be condensed into a liquid. Its specific gravity is, as compared with
hydrogen, 35·37; as compared with air, 2·45; a litre under standard
conditions weighs 3·167 grms. It is soluble in water.
The usual method of preparation is the addition of hydrochloric acid to
bleaching powder, which latter substance is hypochlorite of lime mixed
with calcic chloride and, it may be, a little caustic lime. Another
method is to treat manganese dioxide with hydrochloric acid or to act on
manganese dioxide and common salt with sulphuric acid.
Accidents are liable to occur with chlorine gas from its extensive use
as a disinfectant and also in its manufacture. In the “Weldon” process
of manufacturing bleaching powder, a thick layer of lime is placed on
the floor of special chambers; chlorine gas is passed into these
chambers for about four days; then the gas is turned off; the unabsorbed
gas is drawn off by an exhaust or absorbed by a lime distributor and the
doors opened. Two hours afterwards the men go in to pack the powder. The
packers, in order to be able to work in the chambers, wear a respirator
consisting of about thirty folds of damp flannel; this is tightly bound
round the mouth with the nostrils free and resting upon it. The men are
obliged to inhale the breath through the flannel and exhale through the
nostril, otherwise they would, in technical jargon, be “gassed.” Some
also wear goggles to protect their eyes. Notwithstanding these
precautions they suffer generally from chest complaints.
§ 44. =Effects.=--Free chlorine, in the proportion of 0·04 to 0·06 per
thousand, taken into the lungs is dangerous to life, since directly
chlorine attacks a moist mucous membrane, hydrochloric acid is formed.
The effects of chlorine can hardly be differentiated from hydrochloric
acid gas, and Lehmann found that 1·5 per thousand of this latter gas
affected animals, causing at once uneasiness, evidence of pain with
great dyspnœa, and later coma. The eyes and the mucous membrane of the
nose were attacked. Anatomical changes took place in the cornea, as
evidenced by a white opacity.
In cases that recovered, a purulent discharge came from the nostrils
with occasional necrosis of the mucous membrane. The symptoms in man are
similar; there is great tightness of the breath, irritation of the nose
and eyes, cough and, with small repeated doses, bronchitis with all its
attendant evils. Bleaching powder taken by the mouth is not so deadly.
Hertwig has given 1000 grms. to horses, 30 grms. to sheep and goats, and
15 grms. to dogs without producing death. The symptoms in these cases
were quickening of the pulse and respiration, increased peristaltic
action of the bowels and a stimulation of the kidney secretion. The
urine smelt of chlorine.
§ 45. =Post-mortem Appearances.=--Hyperæmia of the lungs, with
ecchymoses and pneumonic patches with increased secretion of the
bronchial tubes. In the mucous membrane of the stomach, ecchymoses. The
alkalescence of the blood is diminished and there may be external signs
of bleaching. Only exceptionally has any chlorine smell been perceived
in the internal organs.
§ 46. =Detection of Free Chlorine.=--The usual method of detection is to
prepare a solution of iodide of potassium and starch and to soak strips
of filter-paper in this solution. Such a strip, when moistened and
submitted to a chlorine atmosphere, is at once turned blue, because
chlorine displaces iodine from its combination with potassium.
Litmus-paper, indigo blue or other vegetable colours are at once
bleached.
To estimate the amount of chlorine a known volume of the air is drawn
through a solution of potassium iodide, and the amount of iodine set
free, determined by titration with sodic hyposulphite, as detailed at p.
74.
III.--Hydric Sulphide (Sulphuretted Hydrogen).
§ 47. Hydric sulphide, SH₂, is a colourless transparent gas of sp.
gravity 1·178. It burns with a blue flame, forming water and sulphur
dioxide, and is soluble in water; water absorbing about three volumes
at ordinary temperatures. It is decomposed by either chlorine gas or
sulphur dioxide.
It is a common gas as a constituent of the air of sewers or cesspools,
and emanates from moist slag or moist earth containing pyrites or
metallic sulphides; it also occurs whenever albuminous matter putrefies;
hence it is a common constituent of the emanations from corpses of
either man or animals. It has a peculiar and intense odour, generally
compared to that of rotten eggs; this is really not a good comparison,
for it is comparing the gas with itself, rotten eggs always producing
SH₂; it is often associated with ammonium sulphide.
§ 48. =Effects.=--Pure hydric sulphide is never met with out of the
chemist’s laboratory, in which it is a common reagent either as a gas or
in solution; so that the few cases of poisoning by the pure gas, or
rather the pure gas mixed with ordinary air, have been confined to
laboratories.
The greater number of cases have occurred accidentally to men working in
sewers, or cleaning out cesspools and the like. In small quantities it
is always present in the air of towns, as shown by the blackening of any
silver ornament not kept bright by frequent use.
It is distinctly a blood poison, the gas uniting with the alkali of the
blood, and the sulphide thus produced partly decomposing again in the
lung and breathed out as SH₂. Lehmann[60] has studied the effects on
animals; an atmosphere containing from 1 to 3 per thousand of SH₂ kills
rabbits and cats within ten minutes; the symptoms are mainly convulsions
and great dyspnœa. An atmosphere containing from 0·4 to 0·8 per thousand
produces a local irritating action on the mucous membranes of the
respiratory tract, and death follows from an inflammatory œdema of the
lung preceded by convulsions; there is also a paralysis of the nervous
centres. Lehmann has recorded the case of three men who breathed 0·2 per
thousand of SH₂: within from five to eight minutes there was intense
irritation of the eyes, nose, and throat, and after thirty minutes they
were unable to bear the atmosphere any longer. Air containing 0·5 per
thousand of SH₂ is, according to Lehmann, the utmost amount that can be
breathed; this amount causes in half an hour smarting of the eyes, nasal
catarrh, dyspnœa, cough, palpitation, shivering, great muscular
weakness, headache and faintness with cold sweats. 0·7 to 0·8 per
thousand is dangerous to human life, and from 1 to 1·5 per thousand
destroys life rapidly. The symptoms may occur some little time after the
withdrawal of the person from the poisonous atmosphere; for example,
Cahn records the case of a student who prepared SH₂ in a laboratory and
was exposed to the gas for two hours; he then went home to dinner and
the symptoms first commenced in more than an hour after the first
breathing of pure air. Taylor[61] records an unusual case of poisoning
in 1857 at Cleator Moor. Some cottages had been built upon iron slag,
the slag contained sulphides of calcium and iron; a heavy storm of rain
washed through the slag and considerable volumes of SH₂ with, no doubt,
other gases diffused during the night through the cottages and killed
three adults and three children.
[60] K. B. Lehmann, _Arch. f. Hygiene_, Bd. xiv., 1892, 135.
[61] _Principles and Practice of Medl. Jurisp._, vol. ii. 122.
§ 49. =Post-mortem Appearances.=--The so-called apoplectic form of SH₂
poisoning, in which the sufferer dies within a minute or two, shows no
special change. The most frequent change in slower poisoning is,
according to Lehmann, œdema of the lungs. A green colour of the face and
of the whole body is sometimes present, but not constant. A
spectroscopic examination of the blood may also not lead to any
conclusion, the more especially as the spectrum of sulphur methæmoglobin
may occur in any putrid blood. The pupils in some cases have been found
dilated; in others not so.
=Chronic poisoning.=--Chronic poisoning by SH₂ is of considerable
interest in a public health point of view. The symptoms appear to be
conjunctivitis, headache, dyspepsia and anæmia. A predisposition to
boils has also been noted.
§ 50. =Detection.=--Both ammonium and hydric sulphides blacken silver
and filter-paper moistened with acetate of lead solution. To test for
hydric sulphide in air a known quantity may be aspirated through a
little solution of lead acetate. To estimate the quantity a decinormal
solution of iodine in potassium iodide[62] solution is used, and its
exact strength determined by d.n. sodic hyposulphite solution[63]; the
hyposulphite is run in from a burette into a known volume, _e.g._, 50
c.c., of the d.n. iodine solution, until the yellow colour is almost
gone; then a drop or two of fresh starch solution is added and the
hyposulphite run in carefully, drop by drop, until the blue colour of
the starch disappears. If now a known volume of air is drawn through 50
c.c. of the d.n. iodine solution, the reaction I₂ + SH₂ = 2HI + S will
take place, and for every 127 parts of iodine which have been converted
into hydriodic acid 17 parts by weight of SH₂ will be necessary; hence
on titrating the 50 c.c. of d.n. iodine solution, through which air
containing SH₂ has been passed, less hyposulphite will be used than on
the previous occasion, each c.c. of the hyposulphite solution being
equal to 1·11 c.c. or to 1·7 mgrm. of SH₂.
[62] 12·7 grms. of iodine, 16·6 grms. of potassium iodide, dissolved in
a litre of water.
[63] 24·8 grms. of sodic hyposulphite, dissolved in a litre of water.