Jean Rey (1583 - 1645)

Jean Rey

Jean Rey was a French chemist and physician.

Rey received a Master of Arts degree from the Academy of Montauban, then a doctorate from the University of Montpellier, and worked as a physician in his hometown of Le Bug. He was also engaged in chemical research, corresponded with R. Descartes, M. Mersenne and others.

Jean Rey was the first to express the idea of conservation of mass as applied to chemical reactions. While conducting experiments in his brother's forge, he discovered that the mass of lead and tin increases with calcination. The researcher explained this based on the assumption that air has mass and that lead and tin combine with air during calcination. In 1630 Rey published a treatise on this topic, "Experiments to find the reasons for the increase in the weight of tin and lead during calcination". As can be seen from the treatise, he realized that substances are made up of particles. His discovery of the weight of air also made possible the invention of the Torricelli barometer in 1643. Jean Rey also developed a device called the thermoscope, a precursor to the thermometer.