Lavoisier (1743-1794)

• the father of modern chemistry
• best known for a new theory of combustion and respiration in which oxygen is consumed instead of phlogiston being released
• his new theory was based on very careful, quantitative weight measurements
• mass was conserved during chemical reactions
• repeated earlier experiments

Regarding combustion:

• charcoal + oxygen --> ash

Regarding respiration:

• oxygen is taken into the body from the air
• air = mephitic air (nitrogen) + eminently respirable air (oxygen)
• when oxygen is gone, breathing stops

Regarding Boyle's metal calx formation in sealed retorts:

• metal calx does form on heating
• total weight of the sealed retort is unchanged
• when opened, air rushes in and total weight increases
• the increase in total weight matches the difference in weight between the metal and the heavier metal calx
• metal + oxygen --> metal calx

Regarding Priestley's preparation of "dephlogisticated" air:

• mercury calx --> mercury + oxygen

Regarding Cavendish's formation of water:

• inflammable air (hydrogen) + oxygen --> water
• water is a compound not an element
• reverse experiment also performed

Regarding reducing metal calxes:

• metal calx + charcoal --> metal + ash + fixed air

Other contributions of Lavoisier:

• helped introduce a modern naming system, e.g. calx = oxide
• published the first modern chemistry textbook, "Elements of Chemistry", in 1789
• introduced the modern definition of the element (a substance that can not be further decomposed)
• produced a table of elements (it included heat and light)
• explicitly stated the law of conservation of mass during chemical reactions

Lavoisier was beheaded during the French Revolution in 1789.

• Lagrange, "It took them only an instant to cut off that head, and a hundred years may not produce another like it."

Charles