"On chloride of amyle"

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By John Snow, M.D.

This compound was first made by M. Cahours, but was afterwards described more particularly by M. Balard, in the Annales de Chimie, in 1844. It is made by distilling equal quantities of amylic alcohol, or purified fusel oil, and perchloride of phorphorus. It is a colourless liquid, with a slight alliaceous odour, lighter than water, and boiling at 215º Fahr.

I prepared some of this substance a few months ago, and made some experiments with it on guinea-pigs and mice, and also inhaled a drachm of it myself. I ascertained from the experiments on the animals that they require to absorb one-fifth as much of the vapour as the blood is capable of dissolving, in order to be rendered quite insensible. This is exactly the same relative quantity as requires to be absorbed in the case of amylene, and it is not improbable that all the members of the amyle series will be found to possess the same relative physiological strength; for I found that this was the case with several substances of the ethyle series with which I made experiments some years ago. About one part in twenty-eight of what the blood would dissolve was the proportion which required to be absorbed, in order to cause complete insensibility with the compounds of ethyle.

The volatility of chloride of amyle is so moderate that it yields only three cubic inches and three-quarters of vapour at 60º Fahr. to 100 cubic inches of air, even when fully saturated by it. Owing chiefly to this circumstance it causes insensibility, slowly and with difficulty, and its effects pass off slowly; therefore I have not thought of applying it in surgical operations, although the symptoms it induced were very favourable. I think, however, that it might be tried with benefit in neuralgia, and other medical cases, and, possibly, in midwifery; it would, at least, have this advantage, that it could not possibly cause a sudden accident. I have not yet, however, sought an opportunity of applying it. The drachm of it which I inhaled took me ten minutes to consume; it produced a feeling of numbness and drowsiness, which slowly passed off without ill effects.

I should, probably, not yet have brought the subject of chloride of amyle before the Profession, except for what I believe to be a mistake which has been made respecting it. Dr. Simpson brought a substance which he called chloride of amyle before a recent meeting of the Medico-Chirurigical Society of Edinburgh, as a new anæsthetic.* He stated that it did not boil under 120º Fahr., and that it had anæsthetic properties equal to those of the hydride of amyle. (*See Edinburgh Medical Journal, May, 1857, p. 1044.) Now the latter is a powerful anæsthetic, very closely resembling amylene; and from this circumstance, and the very wide difference between the boiling points of chloride of amyle and the liquid which Dr. Simpson exhibited, I feel convinced that the latter was not the real chloride of amyle, but some other compound, or mixture of compounds.

The hydride of amyle is so very difficult to separate from the amylene, which is produced at the same time, that it could probably not be procured in sufficient quantity to apply to the human subject. Moreover, as it boils at 86º Fahr., and would be gaseous in sultry weather and in tropical climates, it would be extremely inconvenient in practice. It is, however, desirable to ascertain the properties of as many volatile narcotic substances as possible.

Sackville-street, May, 1857.