John Dalton

Meteorology, vision and miscellany

Dalton's early life was highly influenced by a prominent Eaglesfield Quaker named Elihu Robinson, a competent meteorologist and instrument maker, who got him interested in problems of mathematics and meteorology. During his years in Kendal, Dalton contributed solutions of problems and questions on various subjects to the Gentlemen's and Ladies' Diaries, and in 1787 he began to keep a meteorological diary in which, during the succeeding 57 years, he entered more than 200,000 observations.^[1] Dalton's first publication was Meteorological Observations and Essays (1793), which contained the seeds of several of his later discoveries. However, in spite of the originality of his treatment, little attention was paid to them by other scholars. A second work by Dalton, Elements of English Grammar, was published in 1801.

In 1794, shortly after his arrival in Manchester, Dalton was elected a member of the Manchester Literary and Philosophical Society, the Lit & Phil, and a few weeks later he communicated his first paper on Extraordinary facts relating to the vision of colours, in which he postulated that shortage in colour perception was caused by discolouration of the liquid medium of the eyeball. In fact, a shortage of colour perception in some people had not even been formally described or officially noticed until Dalton wrote about his own. Although Dalton's theory lost credence in his own lifetime, the thorough and methodical nature of his research into his own visual problem was so broadly recognized that Daltonism became a common term for colour blindness. Examination of his preserved eyeball in 1995 demonstrated that Dalton actually had a less common kind of colour blindness, deuteroanopia, in which medium wavelength sensitive cones are missing (rather than functioning with a mutated form of their pigment, as in the most common type of colour blindness, deuteroanomaly). Besides the green seem one colour which descends pretty uniformly from an intense to a rare yellow, making what I should call different shades of yellow".

This paper was followed by many others on diverse topics on rain and steam, the auxiliary verbs and participles of the English language and the reflection and refraction of light.

Atomic theory

In 1800 he became a secretary of the Manchester Literary and Philosophical Society, and in the following year he presented the first of an important series of papers, entitled Experimental Essays on the constitution of mixed thermal expansion of gases.

The second of these essays opens with the striking remark,

"There can scarcely be a doubt entertained respecting the reducibility of all elastic fluids of whatever kind, into liquids; and we ought not to despair of affecting it in low temperatures and by strong pressures exerted upon the unmixed gases further."

After describing experiments to ascertain the pressure of steam at various points between 0° and 100°F), he concluded from observations on the vapour pressure of six different liquids, that the variation of vapour pressure for all liquids is equivalent, for the same variation of temperature, reckoning from vapour of any given pressure.

In the fourth essay he remarks,

"I see no sufficient reason why we may not conclude that all elastic fluids under the same pressure expand equally by heat and that for any given expansion of mercury, the corresponding expansion of air is proportionally something less, the higher the temperature. It seems, therefore, that general laws respecting the absolute quantity and the nature of heat are more likely to be derived from elastic fluids than from other substances."

He thus enunciated Dalton's law.

The most important of all Dalton's investigations are those concerned with the 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. Here he says:

"Why does not water admit its bulk of every kind of gas alike? This question I have duly considered, and though I am not able to satisfy myself completely I am nearly persuaded that the circumstance depends on the weight and number of the ultimate particles of the several gases."

He proceeds to print his first published table of carbon dioxide, etc. by chemists of the time.

It appears, then, that confronted with the problem of calculating the relative diameter of the atoms of which, he was convinced, all gases were made, he used the results of chemical analysis. Assisted by the assumption that combination always takes place in the simplest possible way, he thus arrived at the idea that chemical combination takes place between particles of different weights, and it was this which differentiated his theory from the historic speculations of the Greeks.

The extension of this idea to substances in general necessarily led him to the law of multiple proportions, and the comparison with experiment brilliantly confirmed his deduction.^[4] It may be noted that in a paper on the proportion of the gases or elastic fluids constituting the atmosphere, read by him in November 1802, the law of multiple proportions appears to be anticipated in the words: "The elements of oxygen may combine with a certain portion of nitrous gas or with twice that portion, but with no intermediate quantity", but there is reason to suspect that this sentence was added some time after the reading of the paper, which was not published till 1805.

Compounds were listed as binary, ternary, etc. in the New System of Chemical Philosophy depending on the number of atoms a compound had in its simplest, empirical form.

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 correspond to modern views, although many others do not.

Dalton used his own symbols to visually represent the atomic structure of compounds. These have made it in New System of Chemical Philosophy where Dalton listed a number of elements, and common compounds.

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.

Unfortunately, Dalton proposed an additional "rule of greatest simplicity" that created controversy, since it could not be independently confirmed.

When atoms combine in only one ratio, "..it must be presumed to be a binary one, unless some cause appear to the contrary"

This was merely an assumption, derived from faith in the simplicity of nature. No evidence was then available to scientists to deduce how many atoms of each element combine to form compound molecules. His rule caused him to assume that the formula for water was OH and ammonia was NH. Because of this, Dalton's experimental data did not support all of the conclusions he drew from it.

But the principles of the theory survived. To be sure, the conviction that atoms cannot be subdivided, created, or destroyed into smaller particles when they are combined , separated, or rearranged in chemical reactions is inconsistent with the existence of nuclear fusion and fission, but such processes are nuclear reactions and not chemical reactions. In addition, the idea that all atoms of a given element are identical in their physical and chemical properties is not literally true, as the different isotopes of an element have varying numbers of neutrons in their nuclei, though the number of protons remains consistent.

Later years

  Dalton communicated his atomic theory to Thomson who, by consent, included an outline of it in the third edition of his System of Chemistry (1807), and Dalton gave a further account of it in the first part of the first volume of his New System of Chemical Philosophy (1808). The second part of this volume appeared in 1810, but the first part of the second volume was not issued till 1827. This delay is not explained by any excess of care in preparation, for much of the matter was out of date and the appendix giving the author's latest views is the only portion of special interest. The second part of vol. ii. never appeared.

Dalton was president of the Lit & Phil from 1817 until his death, contributing 116 memoirs. Of these the earlier are the most important. In one of them, read in 1814, he explains the principles of anhydrates, when dissolved in water, cause no increase in its volume, his inference being that the salt enters into the pores of the water.

Dalton's experimental method

As an investigator, Dalton was often content with rough and inaccurate instruments, though better ones were obtainable. Sir Humphry Davy described him as "a very coarse experimenter", who almost always found the results he required, trusting to his head rather than his hands. On the other hand, historians who have replicated some of his crucial experiments have confirmed Dalton's skill and precision.

In the preface to the second part of vol. i. of his New System he says he had so often been misled by taking for granted the results of others that he determined to write "as little as possible but what I can attest by my own experience", but this independence he carried so far that it sometimes resembled lack of receptivity. Thus he distrusted, and probably never fully accepted, Gay-Lussac's conclusions as to the combining volumes of gases. He held unconventional views on Jöns Jakob Berzelius, although most thought that it was much simpler and more convenient than his own cumbersome system of circular symbols.

Public life

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. However, some witnesses reported that he was deficient in the qualities that make an attractive lecturer, being harsh and indistinct in voice, ineffective in the treatment of his subject, and singularly wanting in the language and power of illustration.

In 1810 Davy asked him to offer himself as a candidate for the fellowship of the Royal Society, but Dalton declined, possibly for financial reasons. However, in 1822 he was proposed without his knowledge, and on election paid the usual fee. Six years previously he had been made a corresponding member of the French Académie des Sciences, and in 1830 he was elected as one of its eight foreign associates in place of Davy.

In 1833 Lord Grey's government conferred on him a pension of £150, raised in 1836 to £300.

Dalton never married and had only a few close friends. He lived for more than a quarter of a century with his friend the Rev. W. Johns (1771–1845), in George Street, Manchester, where his daily round of laboratory work and tuition was broken only by annual excursions to the Lake District and occasional visits to London. In 1822 he paid a short visit to Paris, where he met many distinguished resident scientists. He attended several of the earlier meetings of the British Association at York, Oxford, Dublin and Bristol.

Death and legacy

 

Dalton suffered a minor stroke in 1837, and a second one in 1838 left him with a speech impediment, though he remained able to do experiments. In May 1844 he had yet another stroke; on July 26 he recorded with trembling hand his last meteorological observation. On July 27th, in Manchester, Dalton fell from his bed and was found lifeless by his attendant. Dalton was buried in Manchester in Ardwick cemetery. The cemetery is now a playing field, but pictures of the original grave are in Patterson's book^[5] and the article by Elliott.^[6]

A bust of Dalton, by Chantrey, was publicly subscribed for^[7] and placed in the entrance hall of the Royal Manchester Institution. Chantrey also crafted a large statue of Dalton, now in the Manchester Town Hall.

In honour of Dalton's work, 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.

The University of Manchester established two Dalton Chemical Scholarships, two Dalton Mathematical Scholarships and a Dalton Prize for Natural History.

In his book The 100, Michael H. Hart ranks Dalton as the 32nd most influential person in history.

A lunar crater has been named after Dalton.

See also

• dalton - the atomic mass unit
• daltonism
• Dalton's law

References

1. ^ Smith, R. Angus (1856). Memoir of John Dalton and History of the Atomic Theory. London: H. Bailliere, 279. Retrieved on 2007-12-24. 
2. ^ Roscoe, Henry E.; Arthur Harden (1896). A New View of the Origin of Dalton's Atomic Theory. London: Macmillan. Retrieved on 2007-12-24. 
3. ^ Laboratory notebooks for 1802–1804, under the date 6 September 1803, on p.248
4. ^ Roscoe, Henry E.; Arthur Harden (1896). A New View of the Origin of Dalton's Atomic Theory. London: Macmillan, 50 – 51. Retrieved on 2007-12-24. 
5. ^ Patterson, Elizabeth C. (1970). John Dalton and the Atomic Theory. Garden City, New York: Anchor. 
6. ^ Elliott, T. Lenton (1953). "John Dalton's Grave". Journal of Chemical Education 30: 569. Retrieved on 2007-12-24.
7. ^ Millington, John Price (1906). John Dalton. London: J. M. Dent & Company, 201 – 208. Retrieved on 2007-12-24. 

Bibliography

 

• Greenaway, Frank (1966). John Dalton and the Atom. Ithaca, New York: Cornell University Press. 

• Henry, William C. (1854). Memoirs of the Life and Scientific Researches of John Dalton. London: Cavendish Society. Retrieved on 2007-12-24. 

• Hunt, D. M.; Dulai, K. S. & Bowmaker, J. K. et al. (1995), " ", Science 267: 984 – 988, . Retrieved on 2007-12-24

• Lonsdale, Henry (1874). The Worthies of Cumberland: John Dalton. George Routledge and Sons: George. Retrieved on 2007-12-24. 

• Millington, John Price (1906). John Dalton. London: J. M. Dent & Company. Retrieved on 2007-12-24. 

• Patterson, Elizabeth C. (1970). John Dalton and the Atomic Theory. Garden City, New York: Anchor. 

• Rocke, A. J. (2005). "In Search of El Dorado: John Dalton and the Origins of the Atomic Theory". Social Research 72: 125 – 158. Retrieved on 2007-12-24.

• Roscoe, Henry E. (1895). John Dalton and the Rise of Modern Chemistry. London: Macmillan. Retrieved on 2007-12-24. 

• Roscoe, Henry E.; Arthur Harden (1896). A New View of the Origin of Dalton's Atomic Theory. London: Macmillan. Retrieved on 2007-12-24. 

• Smith, R. Angus (1856). Memoir of John Dalton and History of the Atomic Theory. London: H. Bailliere. Retrieved on 2007-12-24. 

• Smyth, A. L. (1998). John Dalton, 1766-1844: A Bibliography of Works by and About Him, With an Annotated List of His Surviving Apparatus and Personal Effects. - Original edition published by Manchester University Press in 1966

• Thackray, Arnold (1972). John Dalton: Critical Assessments of His Life and Science. Harvard University Press. ISBN 0-674-47525-9. 

• Dalton, John (1893). Foundations of the Atomic Theory. Edinburgh: William F. Clay. Retrieved on 2007-12-24. - Alembic Club reprint with some of Dalton's papers, along with some by William Hyde Wollaston and Thomas Thomson