John Dalton (1766 - 1844) was an English chemist, physicist, and meteorologist best known for introducing the modern atomic theory into chemistry and for providing the first detailed scientific description of colour blindness, a condition later named Daltonism in his honour. [1] Working largely outside the established scientific institutions of his day, he argued that matter is composed of indivisible atoms whose relative weights could be measured, giving chemistry a quantitative foundation.
Early life and education
Dalton was born on 6 September 1766 in Cumberland, in the north-west of England, into a modest Quaker family. Largely self-taught, he showed an early aptitude for mathematics and began teaching at a village school while still a teenager. [2] He later moved to Manchester, where he taught mathematics and natural philosophy and became associated with the town's scientific community, including New College, Manchester.
Meteorology and colour vision
Throughout his life Dalton kept meticulous daily meteorological records, and his early work focused on the weather, the atmosphere, and the behaviour of gases. In 1794 he published an account of his own inability to distinguish certain colours, the first systematic study of colour blindness. [2] Because both he and his brother were affected, he suspected the cause lay in the eye itself; the condition became widely known as Daltonism.
Atomic theory
Dalton's most influential contribution was his atomic theory, developed in the first decade of the nineteenth century and set out in his New System of Chemical Philosophy. He proposed that each chemical element consists of tiny, indivisible particles called atoms, that all atoms of a given element are identical in mass, and that chemical reactions involve the rearrangement of these atoms. [3] By assigning relative atomic weights, he transformed chemistry into a quantitative science.
Gas laws
His interest in the atmosphere led to Dalton's law of partial pressures, which states that the total pressure exerted by a mixture of gases equals the sum of the pressures each gas would exert alone. [3] This work reinforced his conviction that gases are made of discrete particles.
Legacy and honours
Dalton was elected a Fellow of the Royal Society and received one of its Royal Medals, and he was also made a Fellow of the American Academy of Arts and Sciences. [1] He continued his research in Manchester until his death on 27 July 1844. His atomic theory is regarded as a cornerstone of modern chemistry and physics, and his name endures in the unit of atomic mass, the dalton.
