John Dalton

English chemist and physicist

• Born: September 6, 1766
• Birthplace: Eaglesfield, Cumberland, England
• Died: July 27, 1844
• Place of death: Manchester, England

Dalton’s work with gases led him to develop modern atomic theory, and for his contributions he is considered one of the founders of the modern physical sciences.

Early Life

John Dalton, born September 6, 1766, in Eaglesfield, Cumberland, was the second son of Joseph Dalton, a poor weaver, and Deborah Greenup, a woman of vigor and intelligence. His parents came from old Quaker stock, and they had six children, three of whom, Jonathan, John, and Mary, lived to maturity. John was deeply influenced by his mother’s tenacity and frugality. The Society of Friends, which formed a strong social fabric in west Cumberland, was another powerful influence. The Cumberland Quakers emphasized both general education and particular training in natural philosophy, and this provided a favorableF environment for John’s development as a scientist.

Dalton made rapid progress under John Fletcher in the village school, and he quickly attracted the attention of Elihu Robinson, a prominent Quaker naturalist who became Dalton’s patron and lifelong friend. Because of the poverty of his family, Dalton was forced to work for a time as a farm laborer, but in 1781 he was liberated from this way of life by an invitation to replace his elder brother as assistant at Kendal, a boarding school some forty miles from Eaglesfield. The school, newly built by Quakers, had a well-stocked library that contained Sir Isaac Newton’s Philosophiae Naturalis Principia Mathematica (1687; Mathematical Principals of Natural Philosophy, 1729) as well as works of both British and Continental natural philosophers. As at Eaglesfield, so at Kendal, Dalton was fortunate in forming an important friendship. In this case, his patron and friend was the blind natural philosopher John Gough. Under Gough’s tutelage, Dalton made rapid progress in mathematics, meteorology, and botany. In imitation of his master, Dalton started in 1787 keeping a daily meteorological record, a practice he continued until the day of his death.

At Kendal, Dalton began giving a series of public lectures in physics and astronomy. As a teacher, he was clear and orderly, though rather colorless. In physical appearance, he was a tall, gaunt, and awkward man with a prominent chin and nose, and he dressed in the Quaker fashion: knee breeches, gray stockings, and buckled shoes. Though modestly successful at Kendal, he became restless and sought a different profession. He made inquiries about studying medicine at Edinburgh, but he met with discouraging replies. Eventually, Dalton accepted a position as professor of mathematics and natural philosophy in Manchester. He was pleased with this appointment because, in addition to mathematics and natural philosophy, he was allowed to teach chemistry.

In 1800, encouraged by his success in Manchester, Dalton decided to resign his position and open his own “mathematical academy,” where he would offer courses in mathematics, experimental philosophy, and chemistry. This endeavor prospered, and within two years Dalton had enough students to provide him with a modest income. Private teaching on this scale would occupy and support him for the rest of his days.

Life’s Work

Dalton was deeply influenced by the British tradition of popular Newtonianism, a way of visualizing the world through the internal makeup of matter and the operation of short-range forces. As shown so well by Newton, these forces could be described mathematically. Besides his interest in theoretical Newtonian physics, Dalton was involved with more practical concerns—constructing barometers, thermometers, rain gauges, and hygrometers. Dalton produced essays on trade winds, proposed a theory of the aurora borealis, and advanced a theory of rain.

Dalton’s meteorological investigations led him to question how the gases of the air were held together: Were they chemically united or were they physically mixed together in the air just as sand and stones were in the earth? He concluded that gases, composed of particles, were physically mixed together, and this led him to deduce that in a mixture of gases at the same temperature, every gas acts independently (Dalton’s law of partial pressures). It is ironic that in trying to provide a proof for his physical ideas, Dalton discovered the chemical atomic theory. What started as an interest in meteorology ended up as a new approach to chemistry.

To support his theory of mixed gases, Dalton experimented on the proportions of the different gases in the atmosphere. It was this investigation which accidentally raised the whole question of the solubility of gases in water. In 1802, he read a paper to the Manchester Literary and Philosophical Society in which he proposed that carbon dioxide gas (which he called “carbonic acid” gas) was held in water, not by chemical attractive forces but by the pressure of the gas on the surface, forcing it into the pores of the water.

This explanation provoked William Henry, Dalton’s close friend, to begin a series of experiments to discover the order of attractions of gases for water. He eventually found that, at a certain temperature, the volume of a gas taken up by a given volume of water is directly proportional to the pressure of the gas (Henry’s law). Dalton was quick to see the relevance of Henry’s results to his own ideas. He saw the absorption of gases by water as a purely mechanical effect. He realized that the greatest difficulty with the mechanical theory of gas-water solubility came from different gases obeying different laws. Why does water not admit into its bulk every kind of gas in the same way? Dalton answered this question by saying that gases whose particles were lightest were least absorbable and those with greater weight were more absorbable. Therefore it is clear that Dalton’s important decision to investigate the relative weights of atoms arose from his attempt to find experimental support for his theory of mixed gases. The paper that he wrote on this subject in 1803 closed with the very first list of what would come to be called atomic weights.

Dalton’s method of calculating the relative weights of atoms was quite simple. Following the postulates of his theory of mixed gases, he assumed that when two elements come together in a chemical reaction, they do so in the simplest possible way (the rule of greatest simplicity). For example, Dalton knew that water was a compound of oxygen and hydrogen. He reasoned that if water was the only compound of these two elements that could be obtained (and it was at the time), then water must be a binary combination of one hydrogen atom and one oxygen atom (HO). Dalton also gave rules for deciding on formulas when there were two or more compounds of two elements. Armed with this mechanical view of combining atoms, it was easy for Dalton to argue from the experimental knowledge that, in forming nine ounces of water, eight ounces of oxygen combined with one ounce of hydrogen to the statement that the relative weights of their atoms were as eight to one.

When Dalton published his table of atomic weights in a Manchester journal, his theory, for the most part, provoked little reaction. It is true that Humphry Davy at the Royal Institution rejected Dalton’s ideas as speculations that were more ingenious than important. Despite this lack of enthusiasm, Dalton continued to develop his theory, and in 1804 he worked out the formulas for different hydrocarbons. By 1807, he was spreading the news of his system of chemical philosophy (the first part of which was published in 1808, the second part in 1810). With this publication, the chemical atomic theory was launched. Unfortunately, the theory was the climax of Dalton’s scientific creativity, and although he did much work in several scientific fields for the next twenty-five years, the main thrust of his work was in providing atomic weights for known chemical compounds, a problem that would plague chemists for the next fifty years.

Dalton’s scientific studies were nourished by the Manchester Literary and Philosophical Society. This group gave him encouragement, an audience, and recognition. In contrast, the Royal Society was dilatory in making him a member, which they did in 1822 at the urging of some of Dalton’s friends. In 1831, Dalton helped to found the British Association for the Advancement of Science, and he chaired several of its committees. His activity in these scientific societies was halted in 1837 by two severe paralytic attacks, which left him an invalid for the remaining years of his life.

Dalton lived according to regular and rigid habits. He never married, but he was deeply attached to several relatives and associates, in particular, Jonathan, his brother, and Peter Clare, his closest friend. In his later years, Dalton was admired by his countrymen, and after he died on July 27, 1844, he was given a civic funeral with full honors. His body lay in state in the Manchester Town Hall for four days while more than forty thousand people filed past his coffin. This response to his death was an indication of his scientific achievements and a manifestation of the love for him felt by the inhabitants of the city where he spent his happiest years.

Significance

John Dalton sometimes used the word “atom” in the sense of the smallest particle with a particular nature. If the atom were divided any further, it would lose its distinguishing chemical characteristics. Dalton also began, however, to think of atoms in the more radical sense of indivisible particles. With this usage, he provided a new and enormously fruitful model of matter for chemistry, because he was able to develop a way of determining atomic weights.

In his New System of Chemical Philosophy (1808, 1810), Dalton emphasized that chemical analysis is only the separating of ultimate particles, and synthesis is only the uniting of these particles. God created these elementary particles, and they cannot be changed. All the atoms of a particular element are alike, but the atoms of different elements differ. Though the atoms cannot be changed, they can be combined. Water, Dalton wrote, is composed of molecules formed by the union of a single particle of oxygen to a single ultimate particle of hydrogen.

Many chemists were unwilling to adopt Dalton’s chemical atoms. Others used the atomic theory in a pragmatic way, for it helped to make sense of their observations in the laboratory, but they could not grasp its philosophical basis. Some scientists continued to object to atoms well into the twentieth century. They were a minority, however, and a characteristic theme of nineteenth century chemistry was the triumphant march of Dalton’s ideas.

Bibliography

Cardwell, D. S. L., ed. John Dalton and the Progress of Science. Manchester, England: Manchester University Press, 1968. A valuable record of the conference held in Manchester in 1966 to celebrate the bicentennial of Dalton’s birth. It contains articles by scholars on various aspects of Dalton’s achievement. The focus is on the intellectual background to the chemical atomic theory.

Dickinson, Christine, Ian Murray, and David Carden. John Dalton’s Colour Vision Legacy: Selected Proceedings of the International Conference. London: Taylor & Francis, 1997. The proceedings of a conference commemorating the two-hundredth anniversary of Dalton’s description of a newly discovered congenital color vision defect. The text is written by experts in the field and the book is most useful for readers with some knowledge of color vision.

Greenaway, Frank. John Dalton and the Atom. Ithaca, N.Y.: Cornell University Press, 1966. This book, intended for general audiences, explores the reasons that Dalton’s atomic theory had greater impact on the scientific world than other similar theories produced before his time. Greenaway also investigates Dalton’s work in other fields, such as his discovery of color blindness.

McDonnell, John J. The Concept of an Atom from Democritus to John Dalton. Lewiston, N.Y.: Edwin Mellen Press, 1991. Chronicles how scientists throughout the ages have sought to determine if a primary indivisible body exists. Traces these scientific attempts from Democritus in the fifth century b.c.e. through Dalton’s proposed atomic theory of 1802.

Patterson, Elizabeth C. John Dalton and the Atomic Theory: The Biography of a Natural Philosopher. Garden City, N.Y.: Doubleday, 1970. Patterson’s study developed out of a fusion of two of her interests: early nineteenth century science and autodidacts, or self-taught persons. The book was part of the Science Study series for high school students, and it provides an analysis of Dalton and his work for the young student or layman.

Roscoe, H. E., and A. Harden. New View of the Origin of Dalton’s Atomic Theory: A Contribution to Chemical History, Together with Letters and Documents Concerning the Life and Labour of John Dalton, Now for the First Time Published from the Manuscript. London, 1896. Reprint. New York: Johnson Reprint, 1970. Most of Dalton’s manuscripts were destroyed in World War II, but important extracts from Dalton’s notebooks have been preserved in this book. For example, it contains selections from Dalton’s notebooks during the crucial years from 1802 to 1808. The reprint includes an introduction by Arnold Thackray.

Smyth, A. L. John Dalton: A Bibliography of Works by and About Him. Manchester, England: Manchester University Press, 1966. Rev. ed. Brookfield, Vt.: Manchester Library and Philosophical Publications in Association with Ashgate, 1998. This book, more than a bibliography, describes Dalton’s portraits and illustrations and many of his surviving manuscripts. Smyth also provides a useful guide to the enormous secondary literature on Dalton.

Thackray, Arnold. Atoms and Powers: An Essay on Newtonian Matter-Theory and the Development of Chemistry. Cambridge, Mass.: Harvard University Press, 1970. This book provides an excellent treatment of the background by means of which Dalton’s ideas were developed. It traces the development of chemistry from Newton to the radical break with Newtonian chemistry engineered by Dalton.

‗‗‗‗‗‗‗. John Dalton: Critical Assessments of His Life and Science. Cambridge, Mass.: Harvard University Press, 1972. Thackray is a leading scholar on Dalton, and in this book, which relies on new documentation, he situates Dalton in the social and cultural context of the Industrial Revolution. He also uses Dalton to exemplify certain aspects of scientific change.