The first scientist who made significant progress in a new direction in the development of chemistry was the English chemist John Dalton (1766-1844), whose name is closely associated with atomistic theory. At the beginning of the 19th century, Dalton discovers several new experimental patterns: partial pressure law(Dalton's law), law of solubility of gases in liquids(Henry-Dalton's law) and, finally, law of multiple ratios. It is impossible to explain these regularities (primarily the law of multiple ratios) without resorting to the assumption of discreteness of matter. Based on the law of multiple ratios, discovered in 1803, and the law of constancy of composition, Dalton develops his atomic-molecular theory, set forth in the work "The New System of Chemical Philosophy" published in 1808.

The main provisions of Dalton's theory are as follows:

1. All substances are made up of a large number atoms (simple or complex).

2. The atoms of one substance are completely identical. Simple atoms are absolutely immutable and indivisible.

3. Atoms of various elements are able to combine with each other in certain ratios.

4. The most important property atoms is atomic weight.

Already in 1803, the first table of the relative atomic weights of certain elements and compounds appeared in Dalton's laboratory journal; as a starting point, Dalton chooses the atomic weight of hydrogen, taken equal to one. Dalton uses symbols in the form of circles with various figures inside to designate atoms of elements. Subsequently, Dalton repeatedly corrected the atomic weights of the elements, but for most elements he gave incorrect atomic weights.

Dalton was forced to make the assumption that the atoms of different elements in the formation of complex atoms are connected along "principle of maximum simplicity". The essence of the principle is that if there is only one binary compound of two elements, then its molecule (complex atom) is formed by one atom of one element and one atom of another (complex atom is double in Dalton's terminology). Triple and more complex atoms are formed only when there are several compounds formed by two elements. Hence, Dalton assumed that the water molecule consists of one oxygen atom and one hydrogen atom. The result is an underestimation of the atomic weight of oxygen, which in turn leads to an incorrect determination of the atomic weights of metals based on the composition of oxides. The principle of greatest simplicity (reinforced by the authority of Dalton as the creator of the atomic-molecular theory) later played a certain negative role in solving the problem of atomic weights. On the whole, however, Dalton's atomistic theory formed the basis of all further development of natural science.

DALTON John (Dalton J.)
(6.IX.1766 - 27.VII.1844)

John Dalton born into a poor family, possessed great modesty and an extraordinary thirst for knowledge. He did not hold any important university position, he was a simple teacher of mathematics and physics at school and college.

Dalton discovered the gas laws of physics, and in chemistry - the law of multiple ratios, compiled the very first table of relative atomic masses and created the first system of chemical signs for simple and complex substances.

John Dalton - English chemist and physicist, member of the Royal Society of London (since 1822). Born in Eaglesfield, Cumberland. He received his education on his own.
In 1781-1793. - Mathematics teacher at a school in Kendal, from 1793 he taught physics and mathematics at New College in Manchester.

Basic scientific research before 1800-1803. relate to physics, later - to chemistry.
Conducted (since 1787) meteorological observations, investigated the color of the sky, the nature of heat, refraction and reflection of light. As a result, he created the theory of evaporation and mixing of gases.
Described (1794) a visual defect called color blind.

opened three laws, which constituted the essence of his physical atomism gas mixtures: partial pressures gases (1801), dependencies volume of gases at constant pressure temperature(1802, independent of J. L. Gay-Lussac) and dependencies solubility gases from their partial pressures(1803) These works led him to solve the chemical problem of the relationship between the composition and structure of substances.

Put forward and substantiated (1803-1804) atomic theory, or chemical atomism, which explained the empirical law of the constancy of composition.
Theoretically predicted and discovered (1803) law of multiple ratios: if two elements form several compounds, then the masses of one element falling on the same mass of the other are related as integers.

Compiled (1803) the first table of relative atomic masses hydrogen, nitrogen, carbon, sulfur and phosphorus, taking the atomic mass of hydrogen as a unit.

Proposed (1804) chemical sign system for "simple" and "complex" atoms.
Carried out (since 1808) work aimed at clarifying certain provisions and explaining the essence of atomistic theory.

Member of many academies of sciences and scientific societies.

John Dalton was born on September 6, 1766 into a poor family in the northern English village of Eaglesfield. At the age of thirteen, he completed his studies at a local school and became a teacher's assistant himself.

In Kendal, in the autumn of 1781, he became a mathematics teacher.

Scientific research Dalton began in 1787 with observations and experimental study of air. He also studied mathematics, using the rich school library. He began to independently develop new mathematical problems and solutions, and after that he wrote his first scientific works in this area. Four years later he became the principal of the school. During this time he became close to Dr. Charles Hutton, editor of several journals at the Royal Military Academy. Dalton became one of the regular contributors to these almanacs. For his contribution to the development of mathematics and philosophy, he received several high awards. In 1793 he moved to Manchester, where he taught at New College. He brought with him the manuscript of "Meteorological observations and studies. In addition to describing the barometer, thermometer, hygrometer and other instruments and devices, Dalton analyzed in it the processes of cloud formation, evaporation, distribution of precipitation, morning northern winds, and so on.

In 1794 Dalton became a member of the Literary and Philosophical Society. In 1800 he was elected secretary, in May 1808 - vice-president, and from 1817 until the end of his life he was president.

In the autumn of 1794 he gave a lecture on color blindness. Today we call this special defect of vision color blindness.

In 1799 Dalton left New College and became the most expensive private tutor in Manchester. He taught in wealthy families no more than two hours a day, and then engaged in science. His attention was drawn to gases and gas mixtures.

Dalton made several fundamental discoveries - the law of uniform expansion of gases when heated (1802), the law of multiple ratios (1803), the phenomenon of polymers (for example, ethylene and butylene).

On September 6, 1803, Dalton wrote down the first table of atomic weights in his laboratory journal. He first mentioned the atomic theory in a lecture "On the Absorption of Gases by Water and Other Liquids" given on 21 October 1803 at the Manchester Literary and Philosophical Society.

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In December 1803 - May 1804 Dalton gave a course of lectures on relative atomic weights at the Royal Institution in London. Dalton developed the atomic theory in his book, A New System of Chemical Philosophy, published in 1808. In it, he emphasizes two points: all chemical reactions are the result of the combination or division of atoms, all atoms of different elements have different weights.

In 1816, Dalton was elected a corresponding member of the Paris Academy of Sciences. The following year, he was president of the Manchester Society, and in 1818 the British government appointed him scientific expert on the expedition of Sir John Ross, who personally handed over the appointment to the scientist.

But Dalton remained in England. He preferred quiet work in the office, not wanting to scatter and waste precious time. Research to determine atomic weights continued.

In 1822 Dalton became a Fellow of the Royal Society. Shortly thereafter, he left for France.

In 1826, the British government awarded the scientist with a golden order for his discoveries in the field of chemistry and physics, and mainly for the creation of the atomic theory. Dalton was elected an honorary member of the Academy of Sciences in Berlin, the scientific society in Moscow, the Academy in Munich.

In France, to recognize the achievements of the world's foremost scientists, the Paris Academy of Sciences has elected its honorary council.

In 1832 Dalton was awarded the highest distinction of Oxford University. He was awarded the degree of Doctor of Laws. Of the naturalists of that time, only Faraday was awarded such an honor.

In 1833 he was granted a pension. The government's decision was read out at a ceremonial meeting at Cambridge University.

Dalton, despite his advanced age, continued to work hard and make presentations. However, with the advent of old age, illnesses more and more often overcame, it became more and more difficult to work. On July 27, 1844, Dalton died.

John Dalton(September 6, 1766 - July 27, 1844) - English provincial self-taught teacher, chemist, meteorologist, naturalist and Quaker. One of the most famous and respected scientists of his time, who became widely known for his pioneering work in various fields of knowledge. He for the first time (1794) conducted research and described a visual defect that he himself suffered from - color blindness, later named color blindness in his honor; discovered the law of partial pressures (Dalton's law) (1801), the law of uniform expansion of gases when heated (1802), the law of solubility of gases in liquids (Henry-Dalton's law). He established the law of multiple ratios (1803), discovered the phenomenon of polymerization (on the example of ethylene and butylene), introduced the concept of "atomic weight", was the first to calculate the atomic weights (masses) of a number of elements and compiled the first table of their relative atomic weights, thereby laying the foundation for the atomic theory of the structure of matter.

Professor at Manchester College, Oxford University (1793), member of the French Academy of Sciences (1816), president of the Manchester Literary and Philosophical Society (since 1817), member of the Royal Society of London (1822) and the Royal Society of Edinburgh (1835), winner of the Royal Medal (1826).

Youth

John Dalton was born into a Quaker family in Eaglesfield, Cumberland. As the son of a tailor, only at the age of 15 did he begin studying with his older brother Jonathan at a Quaker school in the nearby town of Kendal. By 1790, Dalton more or less decided on his future specialty, choosing between law and medicine, but his plans were met without enthusiasm - dissenter parents were categorically against studying at English universities. Dalton had to stay in Kendal until the spring of 1793, after which he moved to Manchester, where he met John Gough, a blind erudite philosopher, who imparted much of his scientific knowledge to him in an informal setting. This enabled Dalton to secure a teaching position in mathematics and science at New College, Manchester's dissent academy. He remained in this position until 1800, when the deteriorating financial situation of the college forced him to leave; he began to engage in private teaching of mathematics and science.

In his younger years, Dalton was in close contact with the famous Eaglesfield Protestant Elihu Robinson, a professional meteorologist and engineer. Robinson instilled in Dalton an interest in various problems of mathematics and meteorology. During his life in Kendal, Dalton collected solutions to the problems he considered in the book Diaries of Ladies and Gentlemen, and in 1787 began to keep his own meteorological diary, in which he recorded more than 200,000 observations over 57 years. During the same period, Dalton re-developed the theory of atmospheric circulation, previously proposed by George Hadley (George Hadley). The first publication of the scientist was called "Meteorological Observations and Experiments", it contained the germs of ideas for many of his future discoveries. However, despite the originality of his approach, the scientific community did not pay much attention to the works of Dalton. Dalton devotes his second major work to language; it was published under the title “Peculiarities of English grammar» (1801).

color blindness

A healthy person will see the numbers 44 or 49 here, and a patient with deuteranopia, as a rule, will not see anything.

For half of his life, Dalton did not even suspect that something was wrong with his eyesight. He studied optics and chemistry, but discovered his defect through a passion for botany. The fact that he could not tell the difference between a blue flower and a pink one, he attributed to a confusion in the classification of colors, and not to defects in his own eyesight. He noticed that the flower, which in the daytime, in the light of the sun, was sky blue (more precisely, the color that he considered sky blue), in the light of a candle looked dark red. He turned to those around him, but no one saw such a strange transformation, with the exception of his own brother. Thus, Dalton guessed that something was wrong with his vision and that this problem was inherited. In 1794, immediately after arriving in Manchester, Dalton was elected a member of the Manchester Literary and Philosophical Society ("Lit & Phil") and a few weeks later published an article entitled "Unusual Cases of Color Perception", in which he explained the narrowness of the color perception of some people by the discoloration of the liquid substance of the eye. Describing this disease on his own example, Dalton drew the attention of people to it, until that moment they were not aware of its presence. Despite the fact that Dalton's explanation was questioned during his lifetime, the thoroughness of his research into his own disease was so unprecedented that the term "color blindness" was firmly entrenched in this ailment. In 1995, studies were carried out on the preserved eye of John Dalton, during which it turned out that he suffered from a rare form of color blindness - Protanopia. In this case, the eye cannot recognize red, green and green-blue colors. In addition to purple and blue, he could normally recognize only one - yellow, and wrote about it like this:

That part of the picture, which others call red, seems to me like a shadow or just poorly lit. Orange, green, and yellow appear to be shades of the same color, ranging from intense to pale yellow.

After this work, Dalton followed a dozen new ones, devoted to a variety of topics: the color of the sky, the causes of sources of fresh water, the reflection and refraction of light, as well as participles in the English language.

Development of the atomistic concept

In 1800, Dalton became secretary of the Manchester Literary and Philosophical Society, after which he presented a series of reports under the general title "Experiments" on determining the composition of gas mixtures, vapor pressure various substances at different temperatures in vacuum and in air, evaporation of liquids, thermal expansion of gases. Four such articles were printed in the Reports of the Society in 1802. Of particular note is the introduction to Dalton's second work:

One can hardly doubt the possibility of the transition of any gases and their mixtures into a liquid state, it is only necessary to apply appropriate pressure to them or lower the temperature, up to separation into separate components.

After describing the experiments on establishing the pressure of water vapor at various temperatures in the range from 0 to 100 °C, Dalton goes on to discuss the vapor pressure of six other liquids and concludes that the change in vapor pressure is equivalent for all substances for the same change in temperature.

In his fourth work, Dalton writes:

I do not see any objective reasons to consider incorrect the fact that any two gases (elastic medium) at the same initial pressure expand in the same way with a change in temperature. However, for any given expansion of mercury vapor (inelastic medium), the expansion of air will be less. Thus, common law, which would describe the nature of heat and its absolute amount, should be derived on the basis of studying the behavior of elastic media. Gas laws

Joseph Louis Gay-Lussac

Thus, Dalton confirmed Gay-Lussac's law, published in 1802. Within two or three years of reading his papers, Dalton published a series of papers on similar topics, such as the absorption of gases by water and other liquids (1803); at the same time he postulated the law of partial pressures, known as Dalton's law.

The most important of all Dalton's works are those related to the atomistic concept in chemistry, with which his name is most directly connected. It is assumed (by Thomas Thomson) that this theory was developed either in the course of studies of the behavior of ethylene and methane under various conditions, or in the course of the analysis of nitrogen dioxide and monoxide.

The study of Dalton's laboratory records, found in the archives of Lit & Phil, suggests that in the course of the search for an explanation of the law of multiple ratios, the scientist came closer and closer to considering chemical interaction as an elementary act of combining atoms of certain masses. The idea of ​​atoms gradually grew and strengthened in his head, supported by experimental facts obtained in the study of the atmosphere. The first published beginnings of this idea can be found at the very end of his article on the absorption of gases (written October 21, 1803, published 1805). Dalton writes:

Why doesn't water retain its shape like any gas? Having devoted enough time to solving this problem, I cannot give a suitable answer with full confidence, but I am sure that everything depends on the weight and number of microparticles in the substance. Determination of atomic weights

List of chemical symbols for individual elements and their atomic weights compiled by John Dalton in 1808. Some of the symbols used at that time to designate chemical elements date back to the era of alchemy. This list cannot be regarded as a "Periodic Table" since it does not contain repeating (periodic) groups of elements. Some of the substances are not chemical elements, for example, lime (pos. 8 on the left). Dalton calculated the atomic weight of each substance with respect to hydrogen as the lightest, ending his list with mercury, which was erroneously assigned an atomic weight greater than that of lead (pos. 6 on the right)

Various atoms and molecules in John Dalton's book New Course in Chemical Philosophy (1808).

To visualize his theory, Dalton used his own system of symbols, also presented in the New Course in Chemical Philosophy. Continuing research, Dalton after some time published a table of relative atomic weights of six elements - hydrogen, oxygen, nitrogen, carbon, sulfur, phosphorus, taking the mass of hydrogen equal to 1. Note that Dalton did not describe the method by which he determined the relative weights, but in his notes of September 6, 1803, we find a table for calculating these parameters based on data from various chemists on the analysis of water, ammonia, carbon dioxide and other substances.

Faced with the problem of calculating the relative diameter of atoms (of which, as the scientist believed, all gases are composed), Dalton used the results of chemical experiments. Assuming that any chemical transformation always occurs along the simplest path, Dalton comes to the conclusion that a chemical reaction is possible only between particles of different weights. From this moment on, Dalton's concept ceases to be a mere reflection of the ideas of Democritus. The extension of this theory to substances led the researcher to the law of multiple ratios, and the experiment ideally confirmed his conclusion. It is worth noting that the law of multiple ratios was foreseen by Dalton in a report on the description of the content of various gases in the atmosphere, read in November 1802: “Oxygen can combine with a certain amount of nitrogen, or already with twice the same, but there cannot be any intermediate value of the amount of substance.” There is an opinion that this sentence was added some time after reading the report, but it was not published until 1805.

In the New Course of Chemical Philosophy, all substances were divided by Dalton into double, triple, quadruple, etc. (depending on the number of atoms in the molecule). In fact, he proposed to classify the structures of compounds according to the total number of atoms - one atom of element X, when combined with one atom of element Y, gives a double compound. If one atom of the element X is combined with two Y (or vice versa), then such a connection will be triple.

The five main provisions of Dalton's theory The atoms of any element are different from all others, and a characteristic feature in this case is their relative atomic mass All atoms of a given element are identical Atoms of different elements can combine to form chemical compounds, and each compound always has the same ratio of atoms in its composition Atoms cannot be created anew, divided into smaller particles, destroyed by any chemical transformations. Any chemical reaction simply changes the order in which atoms are grouped. see Atomism Chemical elements are made up of small particles called atoms

Dalton also proposed a "rule of greatest simplicity", which, however, has not received independent confirmation: when atoms combine in only one ratio, this indicates the formation of a double compound by them.

It was only an assumption, received by the scientist simply from a belief in the simplicity of the structure of nature. Researchers of that time did not have objective data to determine the number of atoms of each element in a complex compound. However, such "assumptions" are vital for such a theory, because the calculation of relative atomic weights is impossible without knowing chemical formulas connections. However, Dalton's hypothesis led him to define the formula of water as OH (since, from the standpoint of his theory, water is the product of the reaction H + O, and the ratio is always constant); for ammonia, he proposed the formula NH, which, of course, does not correspond to modern ideas.

Despite the internal contradictions that lie at the very heart of Dalton's concept, some of its principles have survived to this day, albeit with minor reservations. For example, atoms really cannot be divided into parts, created or destroyed, but this is true only for chemical reactions. Dalton also did not know about the existence of isotopes of chemical elements, the properties of which are sometimes different from the "classical" ones. Despite all these shortcomings, Dalton's theory (chemical atomics) influenced the future development of chemistry no less than Lavoisier's oxygen theory.

mature years

James Prescott Joule

Dalton showed his theory to T. Thomson, who briefly outlined it in the third edition of his "Course of Chemistry" (1807), and then the scientist himself continued its presentation in the first part of the first volume of the "New Course of Chemical Philosophy" (1808). The second part was published in 1810, but the first part of the second volume was not published until 1827 - the development of chemical theory went much further, the material that remained unpublished was of interest to a very narrow audience even for the scientific community. The second part of the second volume was never published.

In 1817, Dalton became president of Lit & Phil, which he remained until his death, having made 116 reports, of which the earliest are most notable. In one of them, made in 1814, he explains the principles of volumetric analysis, in which he was one of the pioneers. In 1840, his work on phosphates and arsenates (often called one of the weakest) was declared unworthy of publication by the Royal Society, as a result, Dalton had to do it himself. The same fate befell four more of his articles, two of which ("On the amount of acids, alkalis and salts in various salts", "On a new and simple method for analyzing sugar") contained a discovery that Dalton himself considered second in importance after the atomistic concept. Certain anhydrous salts, when dissolved, do not cause an increase in the volume of the solution, respectively, as the scientist wrote, they occupy some “pores” in the structure of water.

James Prescott Joule is a famous student of Dalton.

Experimental Dalton Method

Sir Humphrey Davy, 1830 engraving after a painting by Sir Thomas Lawrence (1769-1830)

Dalton often worked with old and inaccurate instruments, even when better ones were available. Sir Humphry Davy called him "a crude experimenter" who always found the facts he needed, more often taking them from his head than from the actual conditions of the experiment. On the other hand, historians who were directly involved in Dalton repeated a number of the scientist's experiments and spoke, on the contrary, about his skill.

In the preface to the second part of the first volume of The New Deal, Dalton writes that the use of other people's experimental data so often led him astray that in his book he decided to write only about those things that he could personally verify. However, such “independence” resulted in distrust even of generally recognized things. For example, Dalton criticized and, it seems, did not fully accept the Gay-Lussac gas law. The scientist adhered to unconventional views on the nature of chlorine even after the establishment of its composition by G. Davy; he categorically rejected the nomenclature of J. Ya. Berzelius, despite the fact that many considered it much simpler and more convenient than the cumbersome system of Dalton symbols.

Personal life and social activities

John Dalton (from the book: A. Shuster, A. E. Shipley. British Science Legacy. - London, 1917)

Even before the creation of his atomistic concept, Dalton was widely known in scientific circles. In 1804 he was invited to give a course of lectures on natural philosophy at the Royal Institution (London), where he then taught another course in 1809-1810. Some of Dalton's contemporaries questioned his ability to present material in an interesting and beautiful way; John Dalton had a rough, quiet, inexpressive voice, in addition to this, the scientist was too difficult to explain even the simplest things.

In 1810, Sir Humphry Davy invited him to run for election as a Fellow of the Royal Society, but Dalton declined, apparently due to financial difficulties. In 1822, he turned out to be a candidate without knowing it himself, and after the election he paid the due fee. Six years before this event, he became a corresponding member of the French Academy of Sciences, and in 1830 was elected one of the eight foreign members of the academy (in place of Davy).

In 1833 Earl Gray's government gave him a salary of 150 pounds, in 1836 it increased to 300.

Dalton never married and had few friends. For a quarter of a century he lived with his friend R. W. Jones (1771-1845) in George Street, Manchester; his usual course of day, which consisted of laboratory and teaching work, was interrupted only by annual excursions to the Lake District or occasional visits to London. In 1822 he made a short trip to Paris, where he met with various local scientists. Also, a little earlier, he attended a number of scientific conventions of the British Association in York, Oxford, Dublin and Bristol.

End of life, legacy

Passepartout Dalton (circa 1840).

Bust of Dalton by English sculptor Chantray

In 1837, Dalton experienced a mild heart attack, but already in 1838 the next stroke caused him a speech impediment; however, this did not prevent the scientist from continuing his research. In May 1844, he survived another blow, and on July 26, with a trembling hand, he made the last entry in his meteorological journal; On July 27, Dalton was found dead in his apartment in Manchester.

John Dalton was buried at Ardwick Cemetery in Manchester. Now there is a playground on the site of the cemetery, but its photographs have been preserved. A bust of Dalton (by Chantrey) adorns the entrance to King's College Manchester, a statue of Dalton, also by Chantrey, now in Manchester City Hall.

In memory of Dalton's work, some chemists and biochemists informally use the term "dalton" (or Da for short) to refer to the unit of atomic mass of an element (equivalent to 1/12 of the mass of 12C). Also named after the scientist is a street connecting Deansgate and Albert Square in the center of Manchester.

One of the buildings on the territory of the University of Manchester is named after John Dalton. It houses the Faculty of Technology and hosts most of the lectures on natural science subjects. At the exit of the building there is a statue of Dalton, moved here from London (the work of William Theed, 1855, until 1966 soyal on Piccadilly Square).

The student residence building at the University of Manchester also bears Dalton's name. The university has established various Dalton grants: two in chemistry, two in mathematics, and the Dalton Prize in Natural History. There is also the Dalton Medal, issued periodically by the Manchester Literary and Philosophical Society (a total of 12 medals have been issued).

There is a crater on the Moon named after him.

Most of John Dalton's work was destroyed in the bombing of Manchester on 24 December 1940. Isaac Asimov wrote about this: “It is not only the living who die in war.”

Ministry of Education of Ukraine

Mariupol city lyceum

Abstract on the topic:

John Dalton

(1766 – 1844)

Mariupol

John Dalton was born on September 6, 1766, the son of a country Quaker weaver, and did not go to school until he was 12 years old. He received a scientific education on his own, since the doors of Oxford and Cambridge were then open only to members of the Anglican Church, and by the age of 15 he had achieved such success that he got a job as a teacher of mathematics at a school in Kendal. In 1793, he became a teacher of natural philosophy (as physics was called in English colleges) and mathematics at Manchester College, where the famous utopian socialist Robert Owen introduced him to the Manchester Literary and Philosophical Society. Later, another famous Manchester man, Joel, was a member of this society, and in the 20th century. At a meeting of this society, Ernst Rutherford made a report on his experiments that led to the discovery of the nuclear model of the atom. Dalton in 1800 became the secretary of the society, and from 1817 his chairman.

Observing atmospheric phenomena, Dalton became interested in the composition of the air. The study of the composition and properties of air led him to the discovery of gas laws:

Named after him, the law of independence of the partial pressures of the components of a mixture (1801);

A few months before Gay-Lussac, he established the law of thermal expansion of gases (1802);

The law of solubility of gases in liquids (1803).

These laws became important milestones on the way to the creation of the theory of the composition of gases - physical atomism. Having accepted the hypothesis of different sizes of gas atoms surrounded by a thermal shell, Dalton explained such physical phenomena as the expansion of gases during heating, the nature of gas diffusion, and the dependence of their pressure on external conditions. In 1803, Dalton, guided by the atomistic hypothesis, derived the law of multiple ratios and proved it using the example of hydrocarbon compounds - methane and ethylene.

The difference in the size of gas atoms led Dalton to the need to admit their different mass (weight). Thus, in 1803, he moved from physical atomism to the creation of chemical atomism. The main provisions of Dalton's chemical atomistics were the following:

1. Matter consists of the smallest particles - indivisible atoms, which are neither created nor destroyed.

2. All atoms of one element are the same in size and have the same mass (weight).

3. Atoms of different elements have different masses and sizes.

4. Complex particles ("complex atom") consist of a certain number of different atoms included in this substance.

5. The mass of a complex particle is determined by the sum of the masses of its constituent atoms of the elements.

Having based his atomistic theory on the concept of relative atomic weight (mass), Dalton introduced into chemistry a quantitative characteristic of atoms and thereby finally proved their materiality. Atomic mass later became one of the main characteristics of substances. Dalton believed that the atoms of different elements have different sizes and masses. Mistakenly assuming that one oxygen atom is part of the water molecule, he incorrectly determined the atomic weights of oxygen and nitrogen. But Dalton was the first to draw up a table of atomic weights.

In 1803, Dalton compiled the first table of the relative atomic and molecular masses of substances and introduced chemical symbolism, though not entirely successful and replaced in chemistry by the more convenient symbolism of Berzelius (1779 - 1848). He took the atomic mass of hydrogen as a unit. In this table, the relative masses of hydrogen, oxygen, nitrogen, carbon, ammonia, sulfur oxides, nitrogen and other substances were first established.

The merit of Dalton in the development of chemistry is enormous: he first made atomistics the basis of chemical knowledge and outlined the right way to quantitatively determine the composition of substances.

John Dalton also contributed to the development of medicine, first describing in detail in 1794 the visual defect of color blindness (later called color blindness), from which he and his brother suffered.

List of used literature:

1. "Course of the history of physics", Moscow, "Prosveshchenie" 1982

2. "Encyclopedic dictionary of a young chemist", Moscow, "Pedagogy", 1990

3. "Polytechnic Dictionary", Moscow, "Soviet Encyclopedia" 1989