who came up with the conservation of mass
Conservation of mass By the 18th century the principle of conservation of mass during chemical reactions was widely used and was an important assumption during experiments, even before a definition was formally established,[9] as can be seen in the works of Joseph Black, Henry Cavendish, and Jean Rey.[10] The first to outline the principle was given by Mikhail Lomonosov in 1756. He demonstrated it by experiments and had discussed the principle before in 1774 in correspondence with Leonhard Euler, though his claim on the subject is sometimes challenged.[11][12] A more refined series of experiments were later carried out by Antoine Lavoisier who expressed his conclusion in 1773 and popularized the principle of conservation of mass. The demonstrations of the principle led alternatives theories obsolete, like the phlogiston theory that claimed that mass could be gained or lost in combustion and heat processes.