48 Conservation of Matter
He weighed the flask (and the tin inside) before heating it over a burner. A thick layer
of calx (a light gray tarnish) formed on the tin as it heated—as Boyle had described in his
paper.
Lavoisier turned off the burner, let the flask cool, and then reweighed it. The flask had
not changed weight. He pried off the flask’s lid. Air rushed in, as if into a partial vacuum.
Antoine removed and weighed the calx-covered tin. It had gained two grams of weight (as
had Boyle’s).
Lavoisier deduced that the weight had to have come from the air inside the flask and
that was why new air rushed into the flask when he opened it. The tin gained two grams as it
mixed with air to form calx. When he opened the lid, two grams of new air rushed in to replace the air that had been absorbed into calx.
He repeated the experiment with a larger piece of tin. However, still only two grams of
air were absorbed into calx. He ran the experiment again and measured the volume of air
that was absorbed into calx—20 percent of the total air inside the flask.
He concluded that only 20 percent of air was capable of bonding with tin. He realized
that this 20 percent of air must be the “pure air” Priestley had discovered in 1774, and
Lavoisier named it “oxygen.”
Through further experiments Lavoisier realized that he had proved something far more
important. Boyle thought weight, or matter, was “created” during experiments. Lavoisier
had proved that matter was neither created nor lost during a chemical reaction. It always
came from someplace and went to someplace. Scientists could always find it if they
measured carefully.
The all-important concept of conservation of matter had been discovered. However,
Lavoisier didn’t release this principle until he published his famed chemistry textbook in 1789.
Fun Facts: The Furnace Constellation (Fornax) was created to honor the
famous French chemist Antoine Lavoisier, who was guillotined during
the French Revolution in 1794.
More to Explore
Donovan, Arthur. Antoine Lavoisier: Science Administration and Revolution. New
York: Cambridge University Press, 1996.
Grey, Vivian. The Chemist Who Lost His Head. Coward, McCann & Geoghegan, New
York, 1982.
Holmes, Lawrence. Antoine Lavoisier: The Next Crucial Year or the Source of His
Quantitative Method of Chemistry. Collingdale, PA: Diane Publishing Co., 1998.
Kjelle, Marylou. Antoine Lavoisier: Father of Chemistry. Hockessin, DE: Mitchell
Lane, 2004.
Riedman, Sarah. Antoine Lavoisier: Scientist and Citizen. Scarborough, ON: Nelson,
1995.
Susac, Andrew. The Clock, the Balance, and the Guillotine: The Life of Antoine
Lavoisier. New York: Doubleday, 1995.
Yount, Lisa. Antoine Lavoisier: Founder of Modern Chemistry. Berkeley Heights, NJ:
Enslow, 2001.