John Dalton (6.09.1766-27.07.1844) was an English chemist and physicist and a Fellow of the Royal Society (1822). He was born in Eaglesfield. He was self-taught. He was a teacher of mathematics in Manchester.
His research in physics was in the field of molecular physics. He observed (1800) that the temperature of air rises when it is compressed adiabatically and falls when it expands. He studied the properties of water vapour and was the first to point out (1801) the difference between saturated and superheated vapours. In 1801 he discovered the law of the partial pressures of gases, in 1803 the law by which the dissolution of gases depends on their partial pressure (Dalton's law), and in 1801, independently of J. Gay-Lussac, one of the gas laws: at constant pressure all gases expand equally as the temperature rises.
Dalton's great contribution was the development of atomistic ideas as applied to chemistry. He established that the atoms of one and the same chemical element have identical properties. He introduced the concept of atomic weight and drew up the first table of the atomic weights of the elements (1803). He proposed symbols for the atoms of the chemical elements, but they did not come into general use. In 1794 he was the first to describe the defect of vision which came to be called daltonism. A member of the Paris Academy of Sciences.