I was thinking about phenol the other day. “Very interesting,” I hear you say, “now if you don’t mind I’ve got a fascinating patch of drying paint I need to keep an eye on.” But wait! Bear with me. Phenol is a very interesting molecule. It’s history has a little something for everyone, from lawyers to doctors to advertising copywriters. There are gruesome tales from history, legal wrangles, and even a warning about the dangers of believing everything you read on the internet. So drag yourself away from the eggshell white, find yourself a comfy seat and I’ll begin.

Phenol: a simple molecule with a complicated history.

Phenol is a simple molecule, consisting of a single -OH group attached to what chemists call a benzene ring (the structure of which was, so legend has it, finally determined after the German chemist August Kekulé dreamt of a snake eating its own tail).

You may think you’ve never heard of phenol, less still used it, but chances are you’ve come across the term ‘carbolic soap‘ somewhere. Phenol’s other name is carbolic acid, and it’s the main ingredient in carbolic soap, a mildly disinfectant cleaning agent that used to be a common household product in both Britain and America (in the form of Lifebuoy), was widely used in English state schools up until at least the 1970s, and is distributed to disaster victims for routine hygiene by the Red Cross to this day.

Carbolic soap isn’t so common these days since it has a tendency to irritate the skin and far gentler alternatives are available, although you can still find it in specialist outlets and apparently it’s quite popular in the Caribbean.

Friedlieb Ferdinand Runge

But back to phenol itself. It was discovered in 1834 when it was extracted from coal tar – a by-product of the coal industry – by the chemist Friedlieb Ferdinand Runge, also famous for identifying caffeine.

Joseph Lister

Despite his rather glorious name, Runge is not the best-remembered scientist associated with phenol. That honour almost certainly goes to Joseph Lister who, in the late 19th century, pioneered the technique of antiseptic surgery. It may seem difficult to believe today, but back then surgeons weren’t required to wash their hands before treating patients, and even took pride in the accumulated stains on their surgical gowns. Until Lister’s use of phenol (or carbolic acid), people were more likely to die from infection following the treatment than from the original injury itself. Lister started using phenol to sterilise surgical instruments and wounds and after seeing his results others soon followed, completely changing surgery as we know it today.

In case you’re wondering, Lister had nothing directly to do with the invention of the (phenol-free) mouthwash product that bears his name. It was, however, named after him in honour of his work. Interestingly, Listerine was first marketed as a surgical antiseptic, then a floor cleaner and a cure for gonorrhoea, before it eventually found success as a solution for bad breath.

I mentioned lawyers earlier, and that’s because phenol was instrumental in one of the first examples of contract law: Carlill v Carbolic Smoke Ball Company [1892]. It was the main ingredient of the Carbolic Smoke Ball, an ineffective piece of medical quackery marketed in London in the 19th century as protecting the user against influenza and other ailments. The manufacturer advertised that buyers who found it did not work would be awarded £100.

The Carbolic Smoke Ball Company thought this was nothing more than an inspired piece of advertising, and tried to argue that it was “mere puff” that no reasonable person would take literally. The judge rejected their claims, ruled that the advert made an clear promise, and ordered the company to pay £100 to the unfortunate flu-suffering customer Louisa Carlill. To this day, this case is often cited as an example of the basic principles of contract and how they relate to every day life.

St. Maximilian Kolbe

Phenol also has a darker past, injections of it having been used as a means of execution. In particular, in World War II the Nazis used it in the euthanasia program, Action T4. Phenol was inexpensive, easy to make and fast-acting, and so quickly became the injectable toxin of choice. Famously, the Polish Catholic priest St. Maximilian Kolbe volunteered to undergo three weeks of starvation and dehydration in the place of another inmate and was ultimately executed by phenol injection. Kolbe was canonized on 10 October 1982 by Pope John Paul II; he is the patron saint of drug addicts.

Anyone who’s ever used phenol has probably experienced a phenol burn at some point. It doesn’t always hurt immediately but it slowly starts to burn after a little while, leaving white marks that ultimately turn red and slough off leaving brown-stained skin behind. It is, I should stress, not to be messed with – absorption of phenol through skin can result in phenol toxicity, and if left on the skin it can lead to cell death and gangrene. Even a tiny not-even-remotely-lethal spot is really quite painful. I can’t begin to imagine what death from phenol injection must have been like.

Let’s end on a slightly lighter note. Have you got a bottle of TCP in your medicine cabinet? Many have fallen into the trap of believing that its initials relate directly to its ingredients, and specifically 2,4,6-trichlorophenol. In fact, a number of chemistry textbooks have stated this as hard, cold fact, as did a number of other online sources.

Not so, TCP originally contained trichlorophenylmethyliodosalicyl (not the same thing, and actually some have even wondered if this is truly a compound), but even that was replaced by other active ingredients in the 1950s. These days TCP contains a dilute solution of phenol (about 0.175% w/v) and halogenated phenols (0.68 w/v). So after all that, it does have phenol in it, but it’s not clear whether ‘halogenated phenols’ includes 2,4,6-trichlorophenol.

For a long time many, many websites stated that TCP contained trichlorophenylmethyliodosalicyl, probably traceable back to an earlier Wikipedia article (Wikipedia’s information has since been updated). As Jim Clark points out on his excellent Chemguide website, “The internet is a potentially dangerous tool. One single bit of misinformation can get multiplied over huge numbers of web sites”.

It’s true. Trust no one. (Except The Chronicle Flask of course*.)

(* If you spot an inaccuracy do let me know…)