What was the poison gas created in "Armadale" by Wilkie Collins?

Question

Armadale by Wilkie Collins, describes a method of creating a poison gas

“Do you see that bottle,” he said—“that plump, round, comfortable-looking bottle? Never mind the name of what is beside it; let us stick to the bottle, and distinguish it, if you like, by giving it a name of our own. Suppose we call it ‘our Stout Friend’? Very good. Our Stout Friend, by himself, is a most harmless and useful medicine. He is freely dispensed every day to tens of thousands of patients all over the civilized world. He has made no romantic appearances in courts of law; he has excited no breathless interest in novels; he has played no terrifying part on the stage. There he is, an innocent, inoffensive creature, who troubles nobody with the responsibility of locking him up! But bring him into contact with something else—introduce him to the acquaintance of a certain common mineral substance, of a universally accessible kind, broken into fragments; provide yourself with (say) six doses of our Stout Friend, and pour those doses consecutively on the fragments I have mentioned, at intervals of not less than five minutes. Quantities of little bubbles will rise at every pouring; collect the gas in those bubbles, and convey it into a closed chamber—and let Samson himself be in that closed chamber; our stout Friend will kill him in half an hour! Will kill him slowly, without his seeing anything, without his smelling anything, without his feeling anything but sleepiness. Will kill him, and tell the whole College of Surgeons nothing, if they examine him after death, but that he died of apoplexy or congestion of the lungs!"

While Collins does not describe the chemicals involved, he assures us in the Appendix

Wherever the story touches on questions connected with Law, Medicine, or Chemistry, it has been submitted before publication to the experience of professional men. The kindness of a friend supplied me with a plan of the doctor’s apparatus, and I saw the chemical ingredients at work before I ventured on describing the action of them in the closing scenes of this book.

Intriguingly, he also says

In November, 1865, that is to say, when thirteen monthly parts of “Armadale” had been published, and, I may add, when more than a year and a half had elapsed since the end of the story, as it now appears, was first sketched in my notebook—a vessel lay in the Huskisson Dock at Liverpool which was looked after by one man, who slept on board, in the capacity of shipkeeper. On a certain day in the week this man was found dead in the deck-house. On the next day a second man, who had taken his place, was carried dying to the Northern Hospital. On the third day a third ship-keeper was appointed, and was found dead in the deck-house which had already proved fatal to the other two. The name of that ship was “The Armadale.” And the proceedings at the Inquest proved that the three men had been all suffocated by sleeping in poisoned air!

In this latter case, I would assume that carbon monoxide from a faulty stove was to blame. Can Carbon Monoxide be created in the manner described, or is some other gas more probable?

Answer 1

I suspect the gas is carbon monoxide (not carbon dioxide), which can kill in far lower quantities than carbon dioxide. Note the reference to "six doses" and "collecting the bubbles" - this implies the gas needs to be pretty toxic (as opposed to carbon dioxide of which you would need an enormous quantity if released into a room). One candidate for the reaction described would be as follows: the stout friend is iodoform (a disinfectant that seems to have been in contemporary use) - or indeed any other trihalomethane (eg chloroform, bromoform), and the mineral substance is silver nitrate - other nitrates may have similar effects.

In '“The red brand of murder”: Women Who Kill in Victorian Literature A dissertation presented by Samantha Przybylowicz', footnote 25 suggests (re Armadale):

“Our Stout Friend” is used by Doctor Downward to describe the bottle that the unnamed liquid is in, under the pretense of explaining the chemical reaction to a layperson and a woman. Sutherland notes in the Penguin Classics edition that Collins may be referring to a reaction of carbonic acid gas, as consulted by Alfred Taylor’s Medical Jurisprudence (1849) that Collins was known to have consulted.

Carbonic acid gas however refers to Carbon Dioxide not Carbon Monoxide. However, Carbon Monoxide is also known as "Carbonous Oxide Gas", so it is possible that either Wilkie or Sutherland got confused between the two.

Answer 2

I think carbon dioxide is indicated, as this was used as a means of murder by several late 19th- and early 20th-century mystery writers. Certainly carbon dioxide is invisible and has no smell, as described by Collins (“without his seeing anything, without his smelling anything”) and one of the symptoms of breathing a high concentration of carbon dioxide is an irrestible desire for sleep (“without his feeling anything but sleepiness”). I don’t think this would be the only symptom: modern descriptions of carbon dioxide poisoning give other symptoms—dizziness, tachycardia, impaired coordination—but for the purposes of a mystery story it is close enough.

In ‘The Mystery of the Felwyn Tunnel’ (1898) by L. T. Meade and Robert Eustace, the narrator describes the experience of being overwhelmed by gas as follows

An uncontrollable shudder passed over me. The next moment, to my horror, without the slightest warning, the light I was carrying went out, leaving me in total darkness. I started back, and stumbling against one of the loose boulders reeled against the wall and nearly fell. What was the matter with me? I could hardly stand. I felt giddy and faint, and a horrible sensation of great tightness seized me across the chest. A loud ringing noise sounded in my ears. Struggling madly for breath, and with the fear of impending death upon me, I turned and tried to run from a danger I could neither understand nor grapple with. But before I had taken two steps my legs gave way from under me, and uttering a loud cry I fell insensible to the ground.

_{L. T. Meade and Robert Eustace (1898). ‘The Mystery of the Felwyn Tunnel’. In The Master of Mysteries. Project Gutenberg.}

This is explained as an escape of “choke damp” or “carbonic acid gas” from mine workings:

“Why, this is a natural escape of choke damp. Carbonic acid gas—the deadliest gas imaginable, because it gives no warning of its presence, and it has no smell. It must have collected here during the hours of the night when no train was passing, and gradually rising put out the signal light. The constant rushing of the trains through the cutting all day would temporarily disperse it.”

_{Meade and Eustace.}

“Carbonic acid gas” was the more common name in the 19th century for carbon dioxide. In Wilkie Collins’ description quoted in the question, the "Stout Friend" would then be any acid (for example, vinegar), and the "common mineral substance" would be any carbonate, for example, washing soda (sodium carbonate), or baking soda (sodium bicarbonate). These substances could well be described as “universally accessible”, though I think you would need very large quantities to evolve enough carbon dioxide to kill someone. (Industrial quantities of carbon dioxide are made by other processes.)

Other mystery stories employing carbon dioxide as a means of murder or attempted murder include one by R. Austin Freeman:

In A Silent Witness (1914), the hero is locked in a cellar in a mineral-water factory. “The hissing sound came from three of those great iron bottles, charged under pressure with liquified carbonic acid, which are used by mineral water manufacturers for aerating the water. The miscreant (or lunatic) who had imprisoned me had turned on the taps, and the liquid was escaping and turning into to snow with the cold produced by its own rapid evaporation and expansion. Of course the snow would quickly absorb heat, and, without again liquefying, evaporate into the gaseous form. In a very short time both cellars would be full of the poisonous gas, and I—well, in a word, I was shut up in a lethal chamber.”

And one by Freeman Wills Crofts:

In The End of Andrew Harrison (1938), the victim is killed in his cabin aboard a boat moored on the Thames at Henley. “A mixture of the gas with air [said Dr Jellett] of from five to six per cent upwards was dangerous. Incidentally he might mention that the test of the burning candle was quite unreliable, as a candle would burn in an atmosphere dangerous to human life. The gas prevented the normal oxygenisation of the blood in the lungs, with a speed and completeness proportionate to its purity. For this cause it was really more accurate to speak of suffocation from the gas rather than poisoning, though the latter was the popular phrase. The symptoms varied with different persons, but as a general rule they came on insidiously: producing first drowsiness, then sleep, then unconsciousness gliding imperceptibly into death. In some cases there was discomfort and pain, but this was unusual.”

I think the question is right that the 1865 deaths aboard the Armadale were more likely to be caused by carbon monoxide from a stove or engine with faulty ventilation. Ships using carbon dioxide for refrigeration of cargo don’t seem to have been introduced until the 1890s. However, Collins does not claim that the 1865 deaths were due to the same gas as described in his novel.

Answer 3

I suspect that it will not be possible to answer this question definitively, due to the contradictory information that Wilkie Collins provides in the text. On the whole, I believe that the weight of evidence points towards carbon monoxide being the toxic agent, rather than carbon dioxide, as I will explain below. Probably the contraditions arise from Collins confusing the terms "carbonic acid" (carbon dioxide), and the very similar term "carbonic oxide" (carbon monoxide), having seen them in Alfred Taylor’s Medical Jurisprudence (1849), available to read on google books.

We are first told that the liquid used to fill the purple bottle is yellow in color:

he [the doctor] took from the specimens a handsome purple flask, high and narrow in form, and closed by a glass stopper. This he filled with the yellow liquid...

While impure acids (such as vinegar, for example) can be colored, medical grades would be clear and colorless. The unusual yellow color would indicate some other substance, such as iodoform¹ as suggested in abligh's answer. The poison gas was created and introduced into the victim's room by means of the fumigation apparatus connected to the room, which consisted of:

a large stone jar, having a glass funnel, and a pipe communicating with the wall, inserted in the cork which closed the mouth of it

The jar would contain some solid or powdered substance, and the mode of use was to pour some fluid into the funnel to react with it. This would release gas, which would escape through the pipe into the room the apparatus was connected to.

As noted by Gareth Rees, carbon dioxide can be conveniently produced by adding acid to a carbonate salt. Carbon dioxide has toxicity threshold of about 30000 parts per million,and so to render the air of a reasonably sized room poisonous would require the use of several kilograms of carbonate². The amount of acid necessary would depend on its concentration, but would require several litres. This does not seem consistent with the description of the purple flask, which can be held easily in one hand.

Carbon monoxide, however, has a much lower toxicity level of just 200 ppm. It can be produced by dropping iodoform (a yellow liquid) onto silver nitrate. Both of these substances are commonly used in medicine as disinfectants, consistent with the doctor's description of them as "harmless and useful". It is interesting to note that dropping hydrogen peroxide onto silver nitrate liberates oxygen instead. This is relevant, because the use of the apparatus was either as a fumigant or to provide oxygen for patients with difficulties in breathing:

I noiselessly fumigate one of them; I noiselessly oxygenize the other, by means of a simple Apparatus fixed outside in the corner here

So if the Apparatus had been configured to provide oxygen by loading it with silver nitrate, all the murderer would have to do is swap the hydrogen peroxide for iodoform.

Given how strong the case for carbon monoxide is, why can there still be doubt? The reason is that carbon monoxide poisoning is very obvious in the post-mortem, as the blood remains bright red. In the cases of carbonic oxide poisoning provided by Taylor, for example:

the whole surface of the brain [was] intensely red... the substance of the lungs was of a bright red colour

This would be very obvious to any pathologist, and conflicts with the doctor's assertion that "the whole College of Surgeons" would find nothing suspicious about the death. Here I believe that Collins confused the two substances. Taylor's description of the effects of carbon dioxide poisoning are very similar to that given by Collins:

there is nothing very characteristic in the post-mortem appearances...carbonic acid [i.e. carbon dioxide] acts by inducing apoplexy or cerebral congestion

So I believe that Collins intended the poisonous agent to be carbon monoxide, but confused the issue by ascribing to it the post-mortem effects of carbon dioxide.

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^{1. Another possibility would be sodium hypochlorite, which forms a yellow-green solution. This is used as a disinfectant and bleaching agent, and produces carbon monoxide when reacted with sugars. Sugar, though, does not seem to match the doctor's description of "a common mineral substance".}

^{2. Details of the calculation can be provided on reasonable request.}