John Dalton
Overview
 
John Dalton FRS (6 September 1766 – 27 July 1844) was an English chemist
Chemist
A chemist is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties such as density and acidity. Chemists carefully describe the properties they study in terms of quantities, with detail on the level of molecules and their component atoms...

, meteorologist and physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...

. He is best known for his pioneering work in the development of modern atomic theory
Atomic theory
In chemistry and physics, atomic theory is a theory of the nature of matter, which states that matter is composed of discrete units called atoms, as opposed to the obsolete notion that matter could be divided into any arbitrarily small quantity...

, and his research into colour blindness
Color blindness
Color blindness or color vision deficiency is the inability or decreased ability to see color, or perceive color differences, under lighting conditions when color vision is not normally impaired...

 (sometimes referred to as Daltonism, in his honour).
John Dalton was born into a Quaker family at Eaglesfield
Eaglesfield, Cumbria
Eaglesfield is a small settlement in West Cumbria, England. It is near the A5086 road and is four kilometres southwest of the town of Cockermouth....

, near Cockermouth
Cockermouth
-History:The Romans created a fort at Derventio, now the adjoining village of Papcastle, to protect the river crossing, which had become located on a major route for troops heading towards Hadrian's Wall....

, Cumberland
Cumberland
Cumberland is a historic county of North West England, on the border with Scotland, from the 12th century until 1974. It formed an administrative county from 1889 to 1974 and now forms part of Cumbria....

, England. The son of a weaver, he joined his older brother Jonathan at age 15 in running a Quaker school in nearby Kendal
Kendal
Kendal, anciently known as Kirkby in Kendal or Kirkby Kendal, is a market town and civil parish within the South Lakeland District of Cumbria, England...

.
Encyclopedia
John Dalton FRS (6 September 1766 – 27 July 1844) was an English chemist
Chemist
A chemist is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties such as density and acidity. Chemists carefully describe the properties they study in terms of quantities, with detail on the level of molecules and their component atoms...

, meteorologist and physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...

. He is best known for his pioneering work in the development of modern atomic theory
Atomic theory
In chemistry and physics, atomic theory is a theory of the nature of matter, which states that matter is composed of discrete units called atoms, as opposed to the obsolete notion that matter could be divided into any arbitrarily small quantity...

, and his research into colour blindness
Color blindness
Color blindness or color vision deficiency is the inability or decreased ability to see color, or perceive color differences, under lighting conditions when color vision is not normally impaired...

 (sometimes referred to as Daltonism, in his honour).

Early life

John Dalton was born into a Quaker family at Eaglesfield
Eaglesfield, Cumbria
Eaglesfield is a small settlement in West Cumbria, England. It is near the A5086 road and is four kilometres southwest of the town of Cockermouth....

, near Cockermouth
Cockermouth
-History:The Romans created a fort at Derventio, now the adjoining village of Papcastle, to protect the river crossing, which had become located on a major route for troops heading towards Hadrian's Wall....

, Cumberland
Cumberland
Cumberland is a historic county of North West England, on the border with Scotland, from the 12th century until 1974. It formed an administrative county from 1889 to 1974 and now forms part of Cumbria....

, England. The son of a weaver, he joined his older brother Jonathan at age 15 in running a Quaker school in nearby Kendal
Kendal
Kendal, anciently known as Kirkby in Kendal or Kirkby Kendal, is a market town and civil parish within the South Lakeland District of Cumbria, England...

. Around 1790 Dalton seems to have considered taking up law or medicine, but his projects were not met with encouragement from his relatives – Dissenters
English Dissenters
English Dissenters were Christians who separated from the Church of England in the 16th, 17th and 18th centuries.They originally agitated for a wide reaching Protestant Reformation of the Established Church, and triumphed briefly under Oliver Cromwell....

 were barred from attending or teaching at English universities – and he remained at Kendal until, in the spring of 1793, he moved to Manchester
Manchester
Manchester is a city and metropolitan borough in Greater Manchester, England. According to the Office for National Statistics, the 2010 mid-year population estimate for Manchester was 498,800. Manchester lies within one of the UK's largest metropolitan areas, the metropolitan county of Greater...

. Mainly through John Gough
John Gough (natural philosopher)
John Gough was a blind English natural and experimental philosopher who is known for his own investigations as well as the influence he had on both John Dalton and William Whewell.-Life:...

, a blind philosopher and polymath
Polymath
A polymath is a person whose expertise spans a significant number of different subject areas. In less formal terms, a polymath may simply be someone who is very knowledgeable...

 from whose informal instruction he owed much of his scientific knowledge, Dalton was appointed teacher of mathematics and natural philosophy
Natural philosophy
Natural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...

 at the "New College"
Harris Manchester College, Oxford
Harris Manchester College is one of the constituent colleges of the University of Oxford in the United Kingdom. Formerly known as Manchester College, it is listed in the University Statutes as Manchester Academy and Harris College, and at University ceremonies it is called Collegium de Harris et...

 in Manchester, a dissenting academy. He remained in that position until 1800, when the college's worsening financial situation led him to resign his post and begin a new career in Manchester as a private tutor for mathematics and natural philosophy.

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
Meteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...

. 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
Meteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...

 diary
Diary
A diary is a record with discrete entries arranged by date reporting on what has happened over the course of a day or other period. A personal diary may include a person's experiences, and/or thoughts or feelings, including comment on current events outside the writer's direct experience. Someone...

 in which, during the succeeding 57 years, he entered more than 200,000 observations. He also rediscovered George Hadley
George Hadley
George Hadley was an English lawyer and amateur meteorologist who proposed the atmospheric mechanism by which the Trade Winds are sustained. As a key factor in ensuring that European sailing vessels reached North American shores, understanding the Trade Winds was becoming a matter of great...

's theory of atmospheric circulation (now known as the Hadley cell
Hadley cell
The Hadley cell, named after George Hadley, is a circulation pattern that dominates the tropical atmosphere, with rising motion near the equator, poleward flow 10–15 kilometers above the surface, descending motion in the subtropics, and equatorward flow near the surface...

) around this time. 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.

Colour blindness

In 1794, shortly after his arrival in Manchester, Dalton was elected a member of the Manchester Literary and Philosophical Society
Manchester Literary and Philosophical Society
The Manchester Literary and Philosophical Society, popularly known as the Lit & Phil, is a learned society in Manchester, England.Established in 1781 as the Literary and Philosophical Society of Manchester, by Thomas Percival, Thomas Barnes and Thomas Henry, other prominent members have included...

, the "Lit & Phil", and a few weeks later he communicated his first paper on "Extraordinary facts relating to the vision
Visual perception
Visual perception is the ability to interpret information and surroundings from the effects of visible light reaching the eye. The resulting perception is also known as eyesight, sight, or vision...

 of colours", in which he postulated that shortage in colour perception was caused by discolouration of the liquid medium of the eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

ball. 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 color 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 blue and purple of the spectrum he was able to recognize only one colour, yellow, or, as he says in his paper,
This paper was followed by many others on diverse topics on rain and dew
Dew
[Image:Dew on a flower.jpg|right|220px|thumb|Some dew on an iris in Sequoia National Park]]Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening...

 and the origin of springs
Spring (hydrosphere)
A spring—also known as a rising or resurgence—is a component of the hydrosphere. Specifically, it is any natural situation where water flows to the surface of the earth from underground...

, on heat, the colour of the sky
Sky
The sky is the part of the atmosphere or outer space visible from the surface of any astronomical object. It is difficult to define precisely for several reasons. During daylight, the sky of Earth has the appearance of a pale blue surface because the air scatters the sunlight. The sky is sometimes...

, steam
Steam
Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...

, the auxiliary verb
Auxiliary verb
In linguistics, an auxiliary verb is a verb that gives further semantic or syntactic information about a main or full verb. In English, the extra meaning provided by an auxiliary verb alters the basic meaning of the main verb to make it have one or more of the following functions: passive voice,...

s and participle
Participle
In linguistics, a participle is a word that shares some characteristics of both verbs and adjectives. It can be used in compound verb tenses or voices , or as a modifier...

s of the English language and the reflection
Reflection (physics)
Reflection is the change in direction of a wavefront at an interface between two differentmedia so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves...

 and refraction
Refraction
Refraction is the change in direction of a wave due to a change in its speed. It is essentially a surface phenomenon . The phenomenon is mainly in governance to the law of conservation of energy. The proper explanation would be that due to change of medium, the phase velocity of the wave is changed...

 of light.

Atomic theory

In 1800, Dalton became a secretary of the Manchester Literary and Philosophical Society, and in the following year he orally presented an important series of papers, entitled "Experimental Essays" on the constitution of mixed gases; on the pressure of steam and other vapours at different temperatures, both in a vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...

 and in air
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...

; on evaporation
Evaporation
Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....

; and on the thermal expansion
Thermal expansion
Thermal expansion is the tendency of matter to change in volume in response to a change in temperature.When a substance is heated, its particles begin moving more and thus usually maintain a greater average separation. Materials which contract with increasing temperature are rare; this effect is...

 of gases. These four essays were published in the Memoirs of the Lit & Phil in 1802.

The second of these essays opens with the striking remark,
After describing experiments to ascertain the pressure of steam at various points between 0 and 100 °C (32 and 212 °F), Dalton 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,

Gas laws

He thus enunciated Gay-Lussac's law
Gay-Lussac's law
The expression Gay-Lussac's law is used for each of the two relationships named after the French chemist Joseph Louis Gay-Lussac and which concern the properties of gases, though it is more usually applied to his law of combining volumes, the first listed here...

 or J.A.C. Charles's law
Charles's law
Charles' law is an experimental gas law which describes how gases tend to expand when heated. It was first published by French natural philosopher Joseph Louis Gay-Lussac in 1802, although he credited the discovery to unpublished work from the 1780s by Jacques Charles...

, published in 1802 by Joseph Louis Gay-Lussac
Joseph Louis Gay-Lussac
- External links :* from the American Chemical Society* from the Encyclopædia Britannica, 10th Edition * , Paris...

. In the two or three years following the reading of these essays, Dalton published several papers on similar topics, that on the absorption of gases by water and other liquids (1803), containing his law of partial pressures now known as Dalton's law
Dalton's law
In chemistry and physics, Dalton's law states that the total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of each individual component in a gas mixture...

.

The most important of all Dalton's investigations are those concerned with the atomic theory
Atomic theory
In chemistry and physics, atomic theory is a theory of the nature of matter, which states that matter is composed of discrete units called atoms, as opposed to the obsolete notion that matter could be divided into any arbitrarily small quantity...

 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
Ethylene
Ethylene is a gaseous organic compound with the formula . It is the simplest alkene . Because it contains a carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon. Ethylene is widely used in industry and is also a plant hormone...

 (olefiant gas) and methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

 (carburetted hydrogen) or by analysis of nitrous oxide
Nitrous oxide
Nitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula . It is an oxide of nitrogen. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...

 (protoxide of azote) and nitrogen dioxide
Nitrogen dioxide
Nitrogen dioxide is the chemical compound with the formula it is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odor and is a prominent...

 (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 by his search for an explanation of the law of multiple proportions
Law of multiple proportions
In chemistry, the law of multiple proportions is one of the basic laws of stoichiometry, alongside the law of definite proportions. It is sometimes called Dalton's Law after its discoverer, the English chemist John Dalton.The statement of the law is:...

 to the idea that chemical combination consists in the interaction of atoms of definite and characteristic weight, the idea of atoms arose in his mind as a purely physical concept, forced upon him by study of the physical properties of the atmosphere
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...

 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 21 October 1803, though not published until 1805. Here he says:

Atomic weights

Dalton proceeded to print his first published table of relative atomic weight
Atomic weight
Atomic weight is a dimensionless physical quantity, the ratio of the average mass of atoms of an element to 1/12 of the mass of an atom of carbon-12...

s. Six elements appear in this table, namely hydrogen, oxygen, nitrogen, carbon, sulfur, and phosphorus, with the atom of hydrogen conventionally assumed to weigh 1. Dalton provided no indication in this first paper how he had arrived at these numbers. However, in his laboratory notebook under the date 6 September 1803 there appears a list in which he sets out the relative weights of the atoms of a number of elements, derived from analysis of water, ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

, carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

, 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
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

, such as Democritus
Democritus
Democritus was an Ancient Greek philosopher born in Abdera, Thrace, Greece. He was an influential pre-Socratic philosopher and pupil of Leucippus, who formulated an atomic theory for the cosmos....

 and Lucretius
Lucretius
Titus Lucretius Carus was a Roman poet and philosopher. His only known work is an epic philosophical poem laying out the beliefs of Epicureanism, De rerum natura, translated into English as On the Nature of Things or "On the Nature of the Universe".Virtually no details have come down concerning...

.

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. 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 may have been added some time after the reading of the paper, which was not published until 1805.

Compounds were listed as binary, ternary, quaternary, etc. (molecules composed of two, three, four, etc. atoms) 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

  1. Elements are made of extremely small particles called atom
    Atom
    The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...

    s.
  2. Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
  3. Atoms cannot be subdivided, created, or destroyed.
  4. Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
  5. In chemical reactions, atoms are combined, separated, or rearranged.


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. But this or some other such rule was absolutely necessary to any incipient theory, since one needed an assumed molecular formula in order to calculate relative atomic weights. In any case, Dalton's "rule of greatest simplicity" caused him to assume that the formula for water was OH and ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 was NH, quite different from our modern understanding.

Despite the uncertainty at the heart of Dalton's atomic theory, 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
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...

 and nuclear fission
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...

, 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 precisely true, as we now know that different isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...

s of an element have slightly varying weights. However, Dalton had created a theory of immense power and importance. Indeed, Dalton's innovation was fully as important for the future of the science as Antoine Laurent Lavoisier's oxygen-based chemistry had been.

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.

He 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 volumetric analysis, in which he was one of the earliest workers. In 1840 a paper on the phosphate
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...

s and arsenate
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...

s, often regarded as a weaker work, was refused by the Royal Society
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...

, 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 acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

s, base
Base (chemistry)
For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...

s 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 anhydrates, when dissolved in water, cause no increase in its volume, his inference being that the salt enters into the pores
Porosity
Porosity or void fraction is a measure of the void spaces in a material, and is a fraction of the volume of voids over the total volume, between 0–1, or as a percentage between 0–100%...

 of the water.

James Prescott Joule
James Prescott Joule
James Prescott Joule FRS was an English physicist and brewer, born in Salford, Lancashire. Joule studied the nature of heat, and discovered its relationship to mechanical work . This led to the theory of conservation of energy, which led to the development of the first law of thermodynamics. The...

 was a famous pupil of Dalton.

Dalton's experimental method

As an investigator, Dalton was often content with rough and inaccurate
Accuracy and precision
In the fields of science, engineering, industry and statistics, the accuracy of a measurement system is the degree of closeness of measurements of a quantity to that quantity's actual value. The precision of a measurement system, also called reproducibility or repeatability, is the degree to which...

 instruments, though better ones were obtainable. Sir Humphry Davy
Humphry Davy
Sir Humphry Davy, 1st Baronet FRS MRIA was a British chemist and inventor. He is probably best remembered today for his discoveries of several alkali and alkaline earth metals, as well as contributions to the discoveries of the elemental nature of chlorine and iodine...

 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 Volume 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 chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

. Even after its elementary character had been settled by Davy, he persisted in using the atomic weights he himself had adopted, even when they had been superseded by the more accurate determinations of other chemists. He always objected to the chemical notation devised by Jöns Jakob Berzelius
Jöns Jakob Berzelius
Jöns Jacob Berzelius was a Swedish chemist. He worked out the modern technique of chemical formula notation, and is together with John Dalton, Antoine Lavoisier, and Robert Boyle considered a father of modern chemistry...

, although most thought that it was much simpler and more convenient than his own cumbersome system of circular symbols.

Public and personal 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
Royal Institution
The Royal Institution of Great Britain is an organization devoted to scientific education and research, based in London.-Overview:...

 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, Sir Humphry 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, Earl Grey
Charles Grey, 2nd Earl Grey
Charles Grey, 2nd Earl Grey, KG, PC , known as Viscount Howick between 1806 and 1807, was Prime Minister of the United Kingdom of Great Britain and Ireland from 22 November 1830 to 16 July 1834. A member of the Whig Party, he backed significant reform of the British government and was among the...

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

Dalton never married and had only a few close friends, all in all as a Quaker he lived a modest and unassuming life.

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
Lake District
The Lake District, also commonly known as The Lakes or Lakeland, is a mountainous region in North West England. A popular holiday destination, it is famous not only for its lakes and its mountains but also for its associations with the early 19th century poetry and writings of William Wordsworth...

 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
British Association for the Advancement of Science
frame|right|"The BA" logoThe British Association for the Advancement of Science or the British Science Association, formerly known as the BA, is a learned society with the object of promoting science, directing general attention to scientific matters, and facilitating interaction between...

 at York
York
York is a walled city, situated at the confluence of the Rivers Ouse and Foss in North Yorkshire, England. The city has a rich heritage and has provided the backdrop to major political events throughout much of its two millennia of existence...

, Oxford
Oxford
The city of Oxford is the county town of Oxfordshire, England. The city, made prominent by its medieval university, has a population of just under 165,000, with 153,900 living within the district boundary. It lies about 50 miles north-west of London. The rivers Cherwell and Thames run through...

, Dublin and Bristol
Bristol
Bristol is a city, unitary authority area and ceremonial county in South West England, with an estimated population of 433,100 for the unitary authority in 2009, and a surrounding Larger Urban Zone with an estimated 1,070,000 residents in 2007...

.

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 26 July he recorded with trembling hand his last meteorological observation. On 27 July, in Manchester, Dalton fell from his bed and was found lifeless by his attendant. Approximately 40,000 people filed by his coffin as it was laid in state in the Manchester Town Hall
Manchester Town Hall
Manchester Town Hall is a Victorian-era, Neo-gothic municipal building in Manchester, England. The building functions as the ceremonial headquarters of Manchester City Council and houses a number of local government departments....

. He was buried in Manchester in Ardwick cemetery. The cemetery is now a playing field, but pictures of the original grave are in published materials.

A bust of Dalton, by Chantrey
Francis Legatt Chantrey
Sir Francis Legatt Chantrey was an English sculptor of the Georgian era. He left the Chantrey Bequest or Chantrey Fund for the purchase of works of art for the nation, which was available from 1878 after the death of his widow.-Life:Francis Leggatt Chantrey was born at Norton near Sheffield ,...

, was publicly subscribed for and placed in the entrance hall of the Royal Manchester Institution
Royal Manchester Institution
The Royal Manchester Institution was an English learned society founded on 1 October 1823 at a public meeting held in the Exchange Room by Manchester merchants, local artists and others keen to dispel the image of Manchester as a city lacking in culture and taste.The Institution was housed in a...

. Chantrey also crafted a large statue of Dalton, now in the Manchester Town Hall
Manchester Town Hall
Manchester Town Hall is a Victorian-era, Neo-gothic municipal building in Manchester, England. The building functions as the ceremonial headquarters of Manchester City Council and houses a number of local government departments....

. The statue was erected while Dalton was still alive and it has been said: "He is probably the only scientist who got a statue in his life time".

In honour of Dalton's work, many chemists and biochemists use the (as yet unofficial) unit dalton
Atomic mass unit
The unified atomic mass unit or dalton is a unit that is used for indicating mass on an atomic or molecular scale. It is defined as one twelfth of the rest mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of...

 (abbreviated Da) to denote one atomic mass unit, or 1/12 the weight of a neutral atom of carbon-12
Carbon-12
Carbon-12 is the more abundant of the two stable isotopes of the element carbon, accounting for 98.89% of carbon; it contains 6 protons, 6 neutrons, and 6 electrons....

. There is a John Dalton Street connecting Deansgate
Deansgate
Deansgate is a main road through the city centre of Manchester, England. It runs roughly north–south in a near straight route through the western part of the city centre and is the longest road in the city centre at over one mile long....

 and Albert Square
Albert Square, Manchester
Albert Square is a public square in the centre of Manchester, England.It is dominated by its largest building, Manchester Town Hall , a Victorian Gothic building by Alfred Waterhouse...

 in the centre of Manchester.

Manchester Metropolitan University
Manchester Metropolitan University
Manchester Metropolitan University is a university in North West England. Its headquarters and central campus is in the city of Manchester, but there are outlying facilities in the county of Cheshire. It is the third largest university in the United Kingdom in terms of student numbers, behind the...

 has a building named after John Dalton and occupied by the Faculty of Technology, in which the majority of its Science & Engineering lectures and classes take place. A statue is outside the John Dalton Building of the Manchester Metropolitan University in Chester Street which has been moved from Piccadilly. It was the work of William Theed (after Chantrey) and is dated 1855 (it was in Piccadilly until 1966).

The University of Manchester
University of Manchester
The University of Manchester is a public research university located in Manchester, United Kingdom. It is a "red brick" university and a member of the Russell Group of research-intensive British universities and the N8 Group...

 has a hall of residence called Dalton Hall; it also established two Dalton Chemical Scholarships, two Dalton Mathematical Scholarships, and a Dalton Prize for Natural History. There is a Dalton Medal awarded occasionally by the Manchester Literary and Philosophical Society
Manchester Literary and Philosophical Society
The Manchester Literary and Philosophical Society, popularly known as the Lit & Phil, is a learned society in Manchester, England.Established in 1781 as the Literary and Philosophical Society of Manchester, by Thomas Percival, Thomas Barnes and Thomas Henry, other prominent members have included...

 (only 12 times altogether).

Dalton Township
Dalton Township, Ontario
The Township of Dalton was a municipality located in the northwest corner of the former Victoria County, now the city of Kawartha Lakes, in the Canadian province of Ontario. It was named after Dr...

 in southern Ontario
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....

 was named for Dalton. It has, since 2001, been absorbed into the City of Kawartha Lakes
Kawartha Lakes
The city of Kawartha Lakes is a unitary municipality in Central Ontario, Canada. Although called a city, Kawartha Lakes is the size of a typical Ontarian county and is mostly rural....

. However the township name was used in a massive new park: Dalton Digby Wildlands Provincial Park, itself renamed since 2002.

A lunar crater
Dalton (crater)
Dalton is a lunar impact crater that is located near the western limb of the Moon's near side. It is attached to the eastern rim of the walled plain Einstein, with Balboa lying just to the north and Vasco da Gama due south. The rim of this crater is not heavily eroded, and the interior walls are...

 has been named after Dalton. "Daltonism" became a common term for colour blindness and "Daltonien" is the actual French word for "colour blind".

The inorganic section of the UK's Royal Society of Chemistry
Royal Society of Chemistry
The Royal Society of Chemistry is a learned society in the United Kingdom with the goal of "advancing the chemical sciences." It was formed in 1980 from the merger of the Chemical Society, the Royal Institute of Chemistry, the Faraday Society and the Society for Analytical Chemistry with a new...

 is named after Dalton (Dalton Division), and the Society's academic journal for inorganic chemistry also bears his name (Dalton Transactions
Dalton Transactions
Dalton Transactions is a peer-reviewed scientific journal publishing original research and review articles on all aspects of the chemistry of inorganic, bioinorganic, and organometallic compounds. It is published weekly by the Royal Society of Chemistry...

).

The name Dalton can often be heard in the halls of many Quaker schools, for example, one of the school houses in Coram House, the primary sector of Ackworth School, is called Dalton.

Much of his collected work was damaged during the bombing of the Manchester Literary and Philosophical Society on 24 December 1940. This event prompted Isaac Asimov
Isaac Asimov
Isaac Asimov was an American author and professor of biochemistry at Boston University, best known for his works of science fiction and for his popular science books. Asimov was one of the most prolific writers of all time, having written or edited more than 500 books and an estimated 90,000...

 to say, "John Dalton's records, carefully preserved for a century, were destroyed during the World War II bombing of Manchester
Manchester Blitz
The Manchester Blitz was the heavy bombing of the city of Manchester and its surrounding areas in North West England during the Second World War by the Nazi German Luftwaffe...

. It is not only the living who are killed in war." The damaged papers are now in the John Rylands Library
John Rylands Library
The John Rylands Library is a Victorian Gothic building on Deansgate in Manchester, England. The library, which opened to the public in 1900, was founded by Mrs Enriqueta Augustina Rylands in memory of her late husband, John Rylands...

 having been deposited in the university library by the society.s

See also

  • Atomic mass unit
    Atomic mass unit
    The unified atomic mass unit or dalton is a unit that is used for indicating mass on an atomic or molecular scale. It is defined as one twelfth of the rest mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of...

     (dalton) – the atomic mass unit
  • Dalton Minimum
    Dalton Minimum
    The Dalton Minimum was a period of low solar activity, named after the English meteorologist John Dalton, lasting from about 1790 to 1830. Like the Maunder Minimum and Spörer Minimum, the Dalton Minimum coincided with a period of lower-than-average global temperatures...

     – a period of low solar activity
  • Daltonism
  • Democritus
    Democritus
    Democritus was an Ancient Greek philosopher born in Abdera, Thrace, Greece. He was an influential pre-Socratic philosopher and pupil of Leucippus, who formulated an atomic theory for the cosmos....

  • Pneumatic chemistry
    Pneumatic chemistry
    Pneumatic chemistry is a term most-closely identified with an area of scientific research of the seventeenth, eighteenth, and early nineteenth centuries. Important goals of this work were an understanding of the physical properties of gases and how they relate to chemical reactions and,...


External links

- Alembic Club reprint with some of Dalton's papers, along with some by William Hyde Wollaston
William Hyde Wollaston
William Hyde Wollaston FRS was an English chemist and physicist who is famous for discovering two chemical elements and for developing a way to process platinum ore.-Biography:...

 and Thomas Thomson
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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