An interesting e-mail about TCP received February 2013

If you have come to this page straight from a search engine, it will be meaningless to you unless you first read the page about TCP.

Received from Steve Hunter in February 2013 . . .

Dear Mr Clark,

I read with interest your page on the composition of TCP, and thought you may be interested in some extra information I've dug up on the possible origin of the term "trichlorophenylmethyliodosalicyl", and the pre-1950s composition of TCP.

The following text in Order and chaos in the world of atoms (pp.103-104, Saunders & Clark, 1942) suggests that rather than referring to a particular chemical, it may have been an invented name for the purposes of a tax dodge:

Chemical Names

We have just looked in at the laboratory and watched the chemist at work. But now arises a further point of some importance. If the chemist is to be able to tell his fellow chemists what he has succeeded in making, he must be able to give names to his molecular structures. To the uninitiated, names are by far the most frightening part of organic chemistry. Those who read the labels on bottles of medicine will no doubt have seen exceedingly lengthy words from time to time, such as:


Now, for the most part, these names on medical preparations convey little even to a chemist, for they are not fully descriptive and often may stand for any one of thousands of different substances. Frequently they were only used by the trade in order to avoid the medicine tax, for until very recently a law required that where the "formula" was not disclosed, tax had to be paid. It appears that some officials, not knowing sufficient chemistry to realise that the names were often ambiguous, were frequently prepared to accept names of this kind in the belief that they are genuine disclosures of the exact nature of a preparation.

Records in various pharmacopoeias prior to 1950 are somewhat mixed, with some using the term above, but others indicating a similar composition to that as described on your website. For example the 22nd edition of The Extra Pharmacopoeia (Martindale & Westcott) has this in Volume I (1941):

T.C.P. (British Alkaloids Ltd., London) is stated to be a 1% aqueous solution of "trichlorophenylmethyliodosalicyl" with a R.W. coefficient of 10 calculated on the pure salt. It is a non-toxic antiseptic advocated for local application to wounds, ulcers, boils, burns, chilblains, skin affections, insect bites and stings, nasal catarrh (diluted in 1 in 2 or 3 of water) and conjunctivitis (1 in 10), etc.

but the following in Volume II (1943):

T.C.P. (British Alkaloids Ltd., London). "The perfect antiseptic. For external and internal use. Non-toxic, non-caustic, analgesic, antithermic, endosmotic, keroplastic, non-haemostatic, stable." Formula:- A solution of halogenated phenolic bodies in water made from the following ingredients - Chlorine 0.2%, Iodine 0.11%, Phenol 0.63%, Salicylic Acid 0.045%, Bromine a minute trace.

and also a different brand that refers to both the above name and similar composition:

Surgaseptic (Wands Ltd., Leicester). "Trichlorophenylmethyliodosalicyl in water. The perfect treatment for sore throats, tonsilitis, bad breath, burns, cuts, abrasions." Formula:- Contains halogenized phenolic compounds made from the following ingredients:- Phenol 0.63%, Chlorine 0.22%, Salicylic Acid 0.06%, Iodine 0.15%.

I hope this helps shed a little more light onto the mystery!

Best regards,

Steve Hunter

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© Steve Hunter 2013