Dalton, John (1766-1844), an English chemist, proposed an atomic theory of matter that became a basic theory of modern chemistry. His theory, first presented in 1803, states that each chemical element is composed of its own kind of atoms, all with the same relative weight. It explained why a fixed weight of one substance always combines with a fixed weight of another substance in forming a compound.
Dalton was born in Eaglesfield, near Carlisle. In 1794, Dalton published the first major study of color blindness, an affliction he had. In 1802, he published a law now known as Dalton’s law of partial pressures. The law states that the total pressure exerted by a mixture of gases is the sum of the pressures of all individual gases in the mixture.
See also Atom (The birth of the modern atomic theory); Chemistry (Dalton’s atomic theory).
