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John Dalton (September 6, 1766 – July 27, 1844) was a British chemist and physicist, born at Eaglesfield, near Cockermouth in Cumberland. He is most well known for his advocacy of the atomic theory.
Biography
Early life
John Dalton was born September 6, 1766 in Eaglesfield, Cumberland and received his early education from his father and from John Fletcher, a teacher of the Quaker school at Cumberland, on whose retirement in 1778 he himself started teaching. This youthful venture was not successful, the amount he received in fees being only about five shillings a week, and after two years he took to farm work. But he had received some instruction in mathematics from a distant relative, Elihu Robinson, and in 1781 he left his native village to become helper to his cousin George Bewley, who kept a school at Kendal. There he passed the next twelve years, becoming in 1785, through the retirement of his cousin, joint manager of the school with his elder brother Jonathan. Dalton was unable to attend both Oxford and Cambridge university because they were only open to members of the Church of England.
Meteorology, vision and miscellany
The most important of all Dalton's investigations are those concerned with the atomic theory in chemistry, with which his name is inseparably associated. It has been proposed that this theory was suggested to him either by researches on ethylene (olefiant gas) and methane (carburetted hydrogen) or by analysis of nitrous oxide (protoxide of azote) and nitrogen dioxide (deutoxide of azote), both views resting on the authority of Thomas Thomson. However, a study of Dalton's own laboratory notebooks, discovered in the rooms of the Lit & Phil, concluded that so far from Dalton being led to the idea, that chemical combination consists in the interaction of atoms of definite and characteristic weight, by his search for an explanation of the law of multiple proportions, the idea of atomic structure arose in his mind as a purely physical concept, forced upon him by study of the physical properties of the atmosphere and other gases. The first published indications of this idea are to be found at the end of his paper on the absorption of gases already mentioned, which was read on October 21 1803 though not published till 1805.
He hypothesized the structure of compounds can be represented in whole number ratios. So, one atom of element X combining with one atom of element Y is a binary compound. Furthermore, one atom of element X combining with two elements of Y or vice versa, is a ternary compound. Many of the first compounds listed in the New System of Chemical Philosophy were listed correctly, although others have not.
Many of Dalton's ideas were acquired from other chemists at the time, such as Antoine Lavoisier and William Higgins. However, he was the first to put the ideas into a universal atomic theory, which was undoubtedly his greatest achievement.
Five main points of Dalton's Atomic Theory
- Elements are made of tiny particles called atoms
- All atoms of a given element are identical
- The atoms of a given element are different from those of any other element
- Atoms of one element can combine with atoms of other elements to form compounds. A given compound always has the same relative numbers of types of atoms.
- Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process. A chemical reaction simply changes the way atoms are grouped together.
Death and legacy
Dalton died in Manchester in 1844 of paralysis. The first attack he suffered in 1837, and a second in 1838 left him with a speech impediment, though he remained able to make experiments. In May 1844 he had another stroke; on July 26 he recorded with trembling hand his last meteorological observation, and on the 27th he fell from his bed and was found lifeless by his attendant. A bust of him, by Chantrey, was publicly subscribed for him and placed in the entrance hall of the Manchester Royal Institution.
Dalton had requested that his eyes be examined after his death, in an attempt to discover the cause of his colour-blindness; he had hypothesised that his aqueous humour might be coloured blue. Postmortem examination showed that the humours of the eye were perfectly normal. However, an eye was preserved at the Royal Institution, and a 1990s study on DNA extracted from the eye showed that he had lacked the pigment that gives sensitivity to green; the classic condition known as a deuteranope.
In honor of his work with ratios and chemicals that led to the idea of atoms and atomic weights, many chemists and biochemists use the (as of yet unofficial) unit Dalton (abbreviated Da) to denote one atomic mass unit, or 1/12 the weight of a neutral atom of Carbon-12.
In his book The 100, Michael H. Hart ranks Dalton as the 32nd most influential person in history.
References
- Roscoe & Harden (1896)
Bibliography
- Henry, Life of Dalton, Cavendish Society (1854)
- Angus Smith, Memoir of John Dalton and History of the Atomic Theory
- Roscoe and Harden, A New View of the Origin of Dalton's Atomic Theory (1896)
- Arnold Thackray, John Dalton: Critical Assessments of His Life and Science, Harvard University Press, (1972) ISBN 0674475259
- DM Hunt, KS Dulai, JK Bowmaker, JD Mollon, "The Chemistry of John Dalton's Color Blindness", Science, February 17 1995
External links
- John Dalton Manchester Man exhibit
- Dalton Bicentennial celebrations
- John Dalton Biography
- Template:Nndb name
- e-learning biography: John Dalton
- Biography of John Dalton at SLCC
- Contains additional information and a scanned document from the New System of Chemical Philosophy