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Portrait of John Dalton

Science · Chemistry

John Dalton

1766–1844 · English

Chemistry, physics and meteorology (atomic theory)

John Dalton was a Quaker schoolteacher from Cumberland who spent most of his life in Manchester and laid the foundation of modern atomic theory. Drawing on his meteorological studies of gases, he formulated the law of partial pressures and proposed that each element consists of identical atoms with a characteristic relative weight, publishing the first table of atomic weights. He also gave the first scientific description of colour blindness, which he had himself, sometimes called Daltonism.

How to spot them

  • ▸Atomic theory; first table of relative atomic weights; circular atomic symbols
  • ▸Dalton's law of partial pressures; law of multiple proportions
  • ▸Colour blindness ('Daltonism'), described from his own experience in 1794
  • ▸Quaker from Eaglesfield, Cumberland; Manchester Literary and Philosophical Society
  • ▸The dalton (Da), a unit of atomic mass

Key discoveries & works

A New System of Chemical Philosophy (1808–1827)

Set out his atomic theory, with relative atomic weights and pictorial symbols for atoms

Law of partial pressures (1801)

The total pressure of a gas mixture equals the sum of the pressures each gas would exert alone

Extraordinary Facts relating to the Vision of Colours (1794)

First scientific account of colour blindness, read to the Manchester Literary and Philosophical Society

Law of multiple proportions (1803–1808)

When two elements form more than one compound, the masses of one combining with a fixed mass of the other are in small whole-number ratios

Meteorological Observations and Essays (1793)

His first book; he kept a daily weather diary for some 57 years

Key ideas

  • Elements are made of indivisible atoms; all atoms of one element are identical in weight
  • Compounds form when atoms combine in simple whole-number ratios
  • Chemical reactions rearrange atoms; they are neither created nor destroyed
  • Took hydrogen as the reference, with a relative weight of 1

Quick-fire facts

  • •Born in Eaglesfield, near Cockermouth, Cumberland, into a Quaker family; he was teaching at a Quaker school by the age of about 12
  • •Moved to Manchester in 1793 to teach at the New College, a Dissenting academy
  • •Never married
  • •He asked for his eyes to be examined after death; DNA analysis in the 1990s showed he was a deuteranope
  • •Among the first recipients of the Royal Society's Royal Medal (1826)
  • •Over 40,000 people are said to have filed past his coffin or joined his funeral procession in Manchester
  • •The dalton (symbol Da), equal to the unified atomic mass unit, is named after him

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Sources