Claude Louis Berthollet was a man who lived a long time ago, in the 1700s and 1800s. He was a scientist who was interested in how things worked, especially when it came to chemicals. He was born in France and spent most of his life there.
One of the things that Berthollet is most famous for is his work on chlorine. Chlorine is a chemical that can be very dangerous if you're not careful with it. But Berthollet figured out how to use chlorine to make things like bleach, which is a chemical that people use to clean things.
Berthollet was also interested in how chemicals react with each other. He discovered that sometimes, when you mix two chemicals together, they can create a new chemical that has different properties than the original chemicals. This process is called "chemical synthesis."
Berthollet was very curious and always wanted to know more. He read a lot of books and did a lot of experiments to learn as much as he could about the world around him. Even though he lived a long time ago, he is still remembered today for the important work he did in the field of chemistry.