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ContentsContributions to Nuclear Science
1766 – 1844
British chemist and physicist who developed the atomic theory of matter and hence is known as one of the fathers of modern physical science.
John Dalton was born September 6, 1766 at Eaglesfield, near Cockermouth in the Lake District of Cumberland, Great Britian.1, 5 His father, Joseph Dalton, was a weaver in poor circumstances, who, with his wife (Deborah Greenup), belonged to the Society of Friends; they had three children; Jonathan, John and Mary.7
John received his early education from his father and from John Fletcher, teacher of the Quaker school at Pardshow Hall in Eaglesfield.3, 7 John Fletcher, the master, was a superior man who did not use the rod to hammer in learning. He provided John with a superb background and lifelong quest for knowledge.3 Upon the retirement of Fletcher in 1778, when John Dalton was only 12 years old, he took charge of the Quaker school in Cumberland and two years later taught with his brother at a school in Kendal, where he was to remain for 12 years.1 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. In 1781 he left his native village to become assistant 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. About 1790 he seems to have thought of taking up law or medicine, but his projects met with no encouragement from his relatives and he remained at Kendal till, in the spring of 1793, he moved to Manchester as a tutor at New College where he spent the rest of his life. It was here that John would rise above his country schoolteacher background to do his greatest work.3
In the early days of his teaching, Dalton's way of life was influenced by a wealthy Quaker, Elihu Robinson, a capable meteorologist and instrument maker, who interested him in the problems of mathematics and meteorology.1, 5 During his life, Dalton was fascinated by the earth’s atmosphere.5 His first scientific work, which he began in 1787 and continued until the end of his life, was to keep a diary - which was ultimately to contain 200,000 entries - of meteorological observations recording the changeable climate of the lake district in which he lived.1, 2 He then became interested in preparing collections of botanical and insect species. Stimulated by a spectacular aurora borealis display in 1788, he began observations about aurora phenomena - luminous, sometimes colored displays in the sky caused by electrical disturbances in the atmosphere.
Along with his other researches he also became interested in color blindness, a condition that John Dalton and his brother, Jonathan, shared. In 1794 he was elected a member of the Manchester Literary and Philosophical Society, and a few weeks after election he communicated his first paper on Extraordinary facts relating to the vision of colors, in which he gave the earliest account of the optical peculiarity known as Daltonism or color-blindness. In his essay, Dalton had postulated that deficiency in color perception was caused by discoloration of the liquid medium of the eyeball and summed up its characteristics as observed in himself and others.1, 5, 7 Although Dalton's theory lost credence in his own lifetime, the meticulous, systematic nature of his research was so broadly recognized that Daltonism became a common term for color blindness.
These are only some of the subjects on which he wrote essays that he read before the Philosophical Society: others included such topics as the barometer, thermometer, hygrometer, rainfall, the formation of clouds, evaporation and distribution and character of atmospheric moisture, including the concept of the dew point.1
An indefatigable investigator or researcher, Dalton had an unusual talent for formulating a theory from a variety of data. Although he taught chemistry for six years at New College, he had no experience in chemical research. His early studies on gases led to development of the law of partial pressures (known as Dalton's law; q.v.), which states that the total pressure of a mixture of gases equals the sum of the pressures of the gases in the mixture, each gas acting independently.1 In 1803, while attempting to explain his law of partial pressures, John Dalton started to formulate his most important contribution to science the atomic theory. He was studying nitrogen oxides for Dr. Priestley's test for percentage of nitrogen in the air. Among the reactions he studied were those of nitric oxide with oxygen. He discovered that the reaction can take place in two different proportions in exact ratios, namely:
2NO + O ---> N2O3
NO + O ---> NO2
John stated that oxygen combines with nitrogen sometimes 1 to 1.7 and at other times 1 to 3.4 by weight. On August 4, 1803, he stated the law of multiple proportions: the weights of elements always combine with each other in small whole number ratios. John published his first list of atomic weights and symbols that year, which gave chemistry a language of its own. 3
These experiments also resulted in his theory according to which gas expands as it rises in temperature. On the strength of the data gained in these studies he devised other experiments that proved the solubility of gases in water and the rate of diffusion of gases. His analysis of the atmosphere showed it to be constant in com-position to 15,000 feet. Dalton discovered butylene and determined the composition of ether, finding its correct formula.
Finally, he developed his masterpiece of synthesis - the atomic theory.1 He proposed the Atomic Theory in 1803 which stated that (1) all matter was composed of small indivisible particles termed atoms, (2) atoms of a given element possess unique characteristics and weight, and (3) three types of atoms exist: simple (elements), compound (simple molecules), and complex (complex molecules).4, 6 Dalton's theory was presented in New System of Chemical Philosophy (1808-1827). This work identified chemical elements as a specific type of atom, therefore rejecting Newton's theory of chemical affinities.4
Altogether Dalton contributed 116 memoirs to the Manchester Literary and Philosophical Society, of which from 1817 till his death he was the president. Of these the earlier are the most important works, a few of which are listed below.7
In another paper, read in 1814, Dalton explains the principles of volumetric analysis, in which he was one of the earliest workers. In 1840 a paper on the phosphates and arsenates, which was clearly unworthy of him, was refused by the Royal Society, and he was so incensed that he published it himself. He took the same course soon afterwards with four other papers, two of which On the quantity of acids, bases and salts in different varieties of salts and On a new and easy method of analysing
sugar, contain his discovery, regarded by him as second in importance only to the atomic theory, that certain anhydrous salts when dissolved in water cause no increase in its volume, his inference being that the salt enters into the pores of the water.7
Before he had propounded the atomic theory he had already attained a considerable scientific reputation. In 1804 he was chosen to give a course of lectures on natural philosophy at the Royal Institution in London, where he delivered another course in 1809-1810. In 1810 he was asked by Sir Humphrey Davy to offer himself as a candidate for the fellowship of the Royal Society, but declined, possibly for pecuniary reasons; but in 1822 he was proposed without his knowledge, and on election paid the usual fee.2 Six years previously he had been made a corresponding member of the French Academy of Sciences, and in 1830 he was elected as one of its eight foreign associates in place of Davy.7
John Dalton died on 27 July 1844 of a stroke, after noting the weather conditions for the day in his journal. Dalton had requested that his eyes be examined after his death, in an attempt to discover the cause of his color-blindness; he had hypothesized that his aqueous humor might be colored blue. Postmortem examination showed that the humors of the eye were perfectly normal.7 It was his final experiment and proved that the condition called Daltonism is not caused by the eye itself, but some deficient sensory power.3 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.7