Priestley Isolates Oxygen

Joseph Priestley heated red mercuric oxide using a 12-inch convex lens to focus sunlight, releasing a colorless gas that caused candles to burn brightly and sustained a mouse longer than ordinary air. Working in his laboratory at Bowood House near Calne, Wiltshire, Priestley called the substance dephlogisticated air, interpreting it through the prevailing phlogiston framework. He later demonstrated the experiment for Antoine Lavoisier in Paris, providing the empirical foundation that Lavoisier would use to identify and name oxygen.