Antoine Lavoisier Guillotined

Found guilty of fraud, the French chemist was executed on 8 May 1794.

Antoine Laurent Lavoisier by Pierre Michel Alix, Finnish National Gallery (CC0).

Born into a noble family, the son of an attorney at the Parlement de Paris, Antoine Lavoisier invested his fortune in the Ferme générale, a tax-farming company that collected tax and customs on behalf of the royal government in return for a handsome cut. With his finances secure, the dashing Lavoisier could embark on his study of chemistry, aided by his 13-year-old prodigy of a bride, Marie-Anne Pierrette Paulze, who translated foreign papers for him and kept extensive notes on his work.

Perhaps Lavoisier’s greatest contribution to chemistry was in the development of modern chemical nomenclature and scientific method. He was not, however, averse to borrowing ideas from others and claiming them as his own with new names. As his own biographer delicately puts it: ‘This tendency to use the results of others without acknowledgment ... was characteristic of Lavoisier.’

Among those borrowed results were Henry Cavendish’s discovery of inflammable air (hydrogen) and Joseph Priestley’s isolation of dephlogisticated air (oxygen). It was Lavoisier, however, who combined the two to demonstrate for the first time that water was not an element but a compound of the two gases.

While Lavoisier was unpopular among other scientists, it was his income that proved most troublesome. Despite his support for social reform and public education, his role as a tax farmer was his undoing, being best known in the run-up to the Revolution for having built a wall around Paris to enforce customs duties.

On 24 November 1793, the arrest of all the former tax farmers was ordered on charges of defrauding the state. Lavoisier drafted their combined defence, but the revolutionary court was in no mood to listen to aristocratic tax collectors. The 28 co-defendants were found guilty and guillotined on 8 May 1794, no doubt to the great satisfaction of the pro-Revolutionary Unitarian Joseph Priestley.