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§ 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.