In 1789 Lavoisier published the textbook Traite' elementaire de chimie which firmly established the oxygen theory of combustion and led to the downfall of phlogiston theory. This text also established a new chemical nomenclature still in use today. Priestley's "dephlogisticated air" was renamed oxygen and Cavendish's "inflammable air" was renamed hydrogen. During the development of oxygen theory, Lavoisier established the law of conservation of matter - the total mass does not change during chemical reactions. Lavoisier was executed on the guillotine during the French Revolution.