John Dalton




ENGLISH CHEMIST
1766–1844

The fundamental idea of modern chemistry is that matter is made up of atoms of various sorts, which can be combined and rearranged to produce different, and often novel, materials. The person responsible for "this master-concept of our age" (Greenaway, p. 227) was John Dalton. He applied Newton's idea of small, indivisible atoms to the study of gases in the atmosphere and used it to advance a quantitative explanation of chemical composition. If French chemist Antoine Lavoisier started the chemical revolution, then it was Dalton who put it on a firm foundation. His contemporary, the Swedish chemist Jöns J. Berzelius, said: "If one takes away from Dalton everything but the atomic idea, that will make his name immortal."

John Dalton was born on or about September 6, 1766, to Quaker parents, in Eaglesfield, a remote village in the north of England. He was largely self-educated, and learned most of his mathematics and science by teaching others. He studied mathematics in a local school until the age of 11, started his own school at the age of 12, and at 15 joined his brother Jonathan in teaching at, and later running, a Quaker school in Kendal. The Quakers were a small dissenting (from the established Church of England) sect, and Dalton was thus a nonconformist, like the scientists Joseph Priestley and Michael Faraday. Dalton was taught and influenced by fellow Quakers Elihu Robinson, a wealthy instrument maker, and John Gough, a blind polymath. In Kendal Gough taught the young Dalton Latin, Greek, French, mathematics, and science, and in return Dalton read to him from books and newspapers. Gough encouraged Dalton to study natural phenomena and to keep a meteorological journal, which Dalton began on March 24, 1787. Dalton maintained this journal methodically for the rest of his life, making his last meteorological observations on his deathbed. He made over 200,000 measurements over a period of fifty-seven years, and a neighbor in Manchester is supposed to have said that she was able to set her clock by Dalton's daily appearance to take the temperature. Dalton's meteorological observations launched his scientific career and provided the material for his first book, Meteorological Observations and Essays (1793).

British chemist and physicist John Dalton, who drew up the first list of atomic weights.
British chemist and physicist John Dalton, who drew up the first list of atomic weights.

In 1793 Dalton moved to Manchester, becoming professor of mathematics and natural philosophy at New College. He stayed there until 1799, at which time he resigned in order to devote more time to research. He continued to teach private pupils in order to earn a living. According to legend, a visiting French scientist once traveled to Manchester to meet the famous Dalton. He had difficulty in finding him, finally locating him in a small house in an obscure street. He then had to wait while Dalton finished teaching a lesson in mathematics to a small boy.

Dalton stayed in Manchester for the rest of his life, and it was there that he did most of his important work, the results of which were published in the Memoirs of the Manchester Literary and Philosophical Society (MLPS). His first scientific paper, published by the MLPS in 1798, described his red-green color blindness. Dalton is said to have purchased for his mother a pair of what he thought were dull-colored stockings—Quakers did not wear bright colors—which she could not wear because they were scarlet. This misadventure motivated Dalton to investigate his color recognition deficiency. He was the first to describe red-green color blindness, sometimes known as Daltonism.

Dalton's study of the atmosphere, prompted by his weather measurements, led him in 1803 to his law of partial pressures (in a mixture of gases, each gas acts as an independent entity), and subsequently to the study of the combining of elements. He compared marsh gas (methane, CH 4 ) with olefiant gas (ethane, C 2 H 4 ), and found that ethane contained exactly double the mass of carbon to the same mass of hydrogen. It is this relationship between the two gases that guided him to his law of multiple proportions. He imagined a chemical atomic model, whereby one atom of an element could combine only with one, two, or three atoms (and so on) of a second element, the combinations forming distinct compounds. He visualized atoms as small hard balls and constructed small wooden models to illustrate how they combined. He invented symbols that enabled him (and others) to notate chemical formulas ✷. Dalton drew up the first list of atomic weights. Dalton's ideas about atoms and their combinations were first aired in 1803 at meetings of the MLPS, mentioned in Thomas Thomson's System of Chemistry (1807), and finally published by Dalton in his most important book, New System of Chemical Philosophy (1808).

✷ See an image of Dalton's symbols in the Atoms article.

Dalton's most significant work was done between 1795 and 1805, but fame came later—when the importance of his atomic theory was realized. He became a member of the Royal Society in 1822, received its first Royal Medal in 1826, and was honored with a state pension in 1833, among other honors. He died on July 27, 1844, and 40,000 people attended his funeral.

SEE ALSO Berzelius, JÖns Jakob ; Faraday, Michael ; Lavoisier, Antoine ; Priestley, Joseph .

Peter E. Childs

Bibliography

Cardwell, D. S. L., ed. (1968). John Dalton and the Progress of Science. Manchester, U.K.: Manchester University Press.

Greenaway, Frank (1966). John Dalton and the Atom. London: Heinemann.

Henry, William C. (1854). Life of Dalton. London: The Cavendish Society.

Millington, J. P. (1906). John Dalton. London: J. M. Dent.

Internet Resources

LeMoyne College, Department of Chemistry. Classic Chemistry compiled by Carmen Giunta. "John Dalton (1766–1844): A New System of Chemical Philosophy [excerpts]." Available from http://webserver.lemoyne.edu/faculty/giunta/Dalton.html .

Walnut Valley (California) Unified School District. Diamond Bar High School. "John Dalton." Available from http://dbhs.wvusd.k12.ca.us/AtomicStructure/Dalton.html .

Walnut Valley (California) Unified School District. Diamond Bar High School. "Photo Gallery." Available from http://dbhs.wvusd.k12.ca.us/Gallery/ .



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