Antoine Lavoisier was born in August 26, 1743. He was born into a wealthy family. He first studied math and science. For science he studied astronomy, botany, and geology. Lavoisier explained combustion in terms of chemical reactions. He built a labratory in Paris Arsenal to further his studies. Lavosisier is known as the father of modern chemisty. He created the Phlogiston Theory. This theory explained why weightloss occurs when u burn combustibles because they lose phlogiston. (Phlogiston is a weightless substance released into the air when combustibles are being burned.) Also fires and animals will die in an enclosed space because it fills the air with phlogiston. Charcoal doesn't leave very much residue (when burned) because is mostly made of phlogiston. The problem with this theory is that sometimes when they burned the combustibles the residue left was heavier then before. Lavoisier proved the law of conservation of mass, by showing that mass of the reactants had to equal the mass of the product.
http://mattson.creighton.edu/History_Gas_Chemistry/Lavoisier.html
http://cti.itc.virginia.edu/~meg3c/classes/tcc313/200Rprojs/lavoisier2/home.html#phlogiston