He was born in Ballycommon, County Offaly, to Elizabeth Arabin and lieutenant-colonel Daniel Chenevix of the Royal Irish Artillery.
[1] His sister, Sarah Elizabeth, married Captain Hugh Tuite of Sonna, Co. Westmeath, twice Member of Parliament for that county.
In 1803, in the Philosophical Transactions of the Royal Society, he published a paper asserting that the palladium that the English chemist William Hyde Wollaston had extracted from platinum ore the previous year (and had announced and offered for sale anonymously) was in fact an alloy of mercury and platinum.
On his part, Chenevix published a second paper supporting his result in 1805, by which time he'd made Paris his permanent home.
[3] Later that year, Wollaston publicly revealed his authorship (although he had communicated as much to the Royal Society before Chenevix's second paper)[3] and details of how he had, correctly, isolated the element palladium.
How damaging the affair was to Chenevix's reputation as a chemist in the scientific world has been a discussion point for different writers.
[1] An English translation of a paper he wrote in 1808 for Annales de Chimie was published in London in 1811 as Observations on Mineralogical Systems.
In Paris, in 1816, he met Abbé Faria, who reawakened an interest in animal magnetism that had been dormant since Chenevix's visit to Rotterdam in 1797.