It is London, 1862. French chemist Claude-Auguste Lamy has just been awarded a medal for the ‘discovery of a new and abundant source of thallium’ at the International Exhibition. And British chemist and journalist William Crookes is furious.1–3
After all, he had published a paper in 1861 announcing the discovery of a new element he named thallium. Unimpressed, Lamy counters that Crookes’ sample is merely powder, not pure metal like his. The fight is on with Crookes using his position at Chemical News to attack Lamy.1–3
In 1862, the exhibition committee grudgingly awarded Crookes a medal with the inscription: ‘Thallium, for the discovery of the new element’. In 1863, he was elected a Fellow – and 1913 to 1915 President – of the Royal Society. Similarly, in 1873, Lamy became President of the French Chemical Society.1–3
Although Crookes gets most of the credit, ‘the feud was never resolved’, notes Will Kearney in Distillations Magazine.2
What ‘he’ found
The substance both scientists studied is a tasteless, odourless, silvery-white, heavy metal with the atomic number 81.
Symbolised as Tl, thallium does not usually occur in its free form, but frequently combines with other elements like oxygen, chlorine or sulfur.4–6
Once it is isolated and exposed to air, thallium discolours. Exposure occurs largely via inhalation, ingestion or absorption through the skin. And exposure is a risk, as thallium is one of the most toxic metals in the world. It accumulates in the brain, causing severe damage to the central nervous system.4–6
Poison power
Such toxicity is why thallium was used worldwide as a rat poison and insecticide. It was also used in the US to control prairie dogs and squirrels, until it was banned in 1972.4,5,7,8
But beginning in the early 1900s, thallium’s most notorious application was as a treatment for ringworm of the scalp, a common fungal infection experienced by children. Why? Because dermatologists like London’s G.B. Dowling reported that within about 14 days, thallium causes the hair to fall out ‘in a most dramatic fashion’ – enabling doctors to more easily treat infected follicles.9
Although some children did die from treatment, clinicians continued to support its use into the 20th century.
As late as 1932, Liverpool dermatologist H. McCormick Mitchell reported in the British Medical Journal that ‘I believe thallium has found a permanent place
in the treatment of tinea of the scalp’.10
A novel use
While Mitchell was wrong about tinea, thallium does have a place – in murder mysteries. In her 1952 novel The Pale Horse, Agatha Christie’s villain used it to dispatch victims.3
‘Christie described the symptoms of thallium poisoning very well: lethargy, tingling, numbness of the hands and feet, blackouts, slurred speech, insomnia and general debility, and she is sometimes blamed for bringing this poison to the attention of would-be poisoners,’ notes science writer John Emsley.3
But don’t look for it on the pharmacy shelf. While radioactive thallium-201 is used in medical diagnostic procedures, thallium is heavily restricted in Australia.11
