Antoine Lavoisier (1743-1794) was a French taxman and scientist. He did for chemistry what Galileo did for physics: he made it a hard science by putting ideas to the test with hard numbers.
By the 1700s chemistry had come a long ways from the days when it was called alchemy and men tried to turn lead into gold. But it was still not a proper science. Lavoisier made it one.
Lavoisier loved school as a child. When he grew up he gathered taxes for the king. He was not the one who knocked on your door, he was higher up than that. But everyone knew who he was and knew how he got so rich. He married a beautiful 14-year-old girl.
With his riches he built an amazing laboratory where he worked on his chemistry with the help of his wife. Jefferson, Franklin and Priestley and other leading lights of science visited him there.
But more important than his beautiful laboratory or his beautiful wife was his approach to chemistry:
- An element is any substance that cannot be broken down into simpler substances. Lavoisier listed 32 of them.
- Every substance is itself an element or made up of elements.
- A chemical reaction is when one substance changes into another. This comes from a change in the number or proportion of the elements that make up the substance.
- The conservation of matter: matter is neither created nor destroyed – it just becomes a different sort of substance.
- Measure the weight of everything that goes into a chemical reaction and everything that comes out of it, even the air.
Much of this is now common sense, but it was not in the 1700s. It was Lavoisier who made it so.
With this approach Lavoisier was able to tell which ideas were true and which were false.
One of these false ideas was phlogiston. For over a hundred years science said that things burned because they had phlogiston. Wood is full of phlogiston, which is why it burns so easily. The ash that is left over after the wood is burned has no phlogiston. It has been all used up. That is why you cannot burn ashes.
Lavoisier disproved phlogiston. He heated different kinds of metal inside closed containers until they started to burn and change. When he measured the weight of the containers before and after, there was no change. But the burned metal was now heavier. Instead of losing phlogiston, whatever that is, something from the air must have been added to the metal.
For most this put an end to the idea of phlogiston.
In 1789 he came out with his “Elements of Chemistry”, one of the great works of science.
But that year the king was overthrown and the country went mad, wanting to kill all the king’s men. Lavoisier was one of the king’s men. In 1794 they sent him to the guillotine and cut off his head.