The cause of the increased weight that certain metals experience by calcination, has, at all times, been a subject of speculation and research with chemists and natural philosophers. Cardan, Cæsalpin, Libavius, and many others, formerly endeavoured to explain this phænomenon; but amongst them all, we must, in justice, distinguish John Rey, a physician of Perigord, who lived at the beginning of the last century. His work, perhaps unknown to all the chemists and naturalists of the present day, appears the more deserving to be rescued from oblivion, because the reason which he assigns for the increased weight of the calces of lead and tin, has an immediate relation with that, which is on the point of being acknowledged by all chemists.

John Rey (1583–1645) (or, in French) Jean Rey, was a physician of Périgord, France who in 1630 published a tract on calcination, or oxidation of metals, after being notified by Brun, an apothecary of Bergerac, France, of Brun's experiments (as early as 1629) on the calcination of tin. Brun had melted 2 pounds six ounces of tin, and after 6 hours the resulting calx weighed seven ounces more than the original tin. More than one hundred and forty years before Antoine Lavoisier, John Rey recognized that in the calcination of lead or tin, part of the air provided an increase in mass to the calcined metal oxide. His work was eclipsed first by the phlogiston theory and then later, by Lavoisier's discoveries disproving the existence of phlogiston. Lavoisier's oxygen theory confirmed Rey's earlier report, of which Lavoisier claimed he was unaware. After the presentation of Lavoisier's 1775 memoir at the Académie des sciences, Pierre Bayen (1725-1798) wrote a letter to Abbé François Rozier, director of the journal Observations sur la Physique, sur l'Histoire naturelle and sur les Arts, to ask him to publish an update notice, recognizing the priority Rey's work.