Paris. Lavoisier demonstrates for the first time that the transformation of copper and iron into green copper and rust, respectively, is accompanied by a gain in weight, hypothesizing that these substances absorb something from the air. He will later demonstrate that this “something” is oxygen. Lavoisier had already demonstrated years earlier that diamonds, sulfur, and phosphorus all gain weight when burned in air (taking into account both the ash and the gases emitted, of course).
