Joseph Priestley,1773 Mercury calx actually breaks down into two substances when it is heated, liquid mercury and a strange gas. "what surprised me more than I can well express was that a candle burned in this air with a remarkably vigorous flame.a mouse placed in a sealed container of this gas lived for a longer period of time than a mouse placed in a sealed container of ordinary air. Priestley's discovery revealed that substances could combine together or break apart to form new substances with different properties.For example, a colorless,odorless gas could combine with mercury,a silver metal,to form mercury calx,a red mineral Priestley called the gas he discovered dephlogisticated air would not stick. Mercury calxJoseph Priestley,1773 • Mercury calx actually breaks down into two substances when it is heated, liquid mercury and a strange gas. • “what surprised me more than I can well express was that a candle burned in this air with a remarkably vigorous flame.” a mouse placed in a sealed container of this gas lived for a longer period of time than a mouse placed in a sealed container of ordinary air. • Priestley’s discovery revealed that substances could combine together or break apart to form new substances with different properties. For example, a colorless, odorless gas could combine with mercury, a silver metal, to form mercury calx, a red mineral • Priestley called the gas he discovered dephlogisticated air, but this name would not stick