John Dalton(6 September 1766 – 27 July 1844) was a self-educated English provincial teacher, chemist, meteorologist, naturalist and Quaker. One of the most famous and respected scientists of his time, who became widely known for his innovative work in various fields of knowledge. He was the first (1794) to conduct research and describe a vision 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). Established the law of multiple ratios (1803), discovered the phenomenon of polymerization (using the example of ethylene and butylene), introduced the concept of “atomic weight”, was the first to calculate the atomic weights (mass) of a number of elements and compiled the first table of their relative atomic weights, thereby laying the foundation of the atomic theory structure of matter.
Professor of 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), laureate of the Royal Medal (1826).
Youth
John Dalton was born into a Quaker family in Eaglesfield, Cumberland County. The son of a tailor, it was only at the age of 15 that he began studying with his older brother Jonathan at a Quaker school in the nearby town of Kendal. By 1790, Dalton had more or less decided on his future specialty, choosing between law and medicine, but his plans were met without enthusiasm - his dissenter parents were categorically against studying at English universities. Dalton had to remain in Kendal until the spring of 1793, after which he moved to Manchester, where he met John Gough, a blind polymath philosopher who imparted to him much of his scientific knowledge in an informal setting. This enabled Dalton to obtain a position teaching mathematics and science at New College, a dissenting academy in Manchester. He remained in this position until 1800, when the deteriorating financial situation of the college forced him to resign; He began teaching privately in mathematics and science.
In his youth, Dalton was closely associated 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 he began to keep his own meteorological diary, in which over 57 years he recorded more than 200,000 observations. During the same period, Dalton re-developed the theory of atmospheric circulation , previously proposed by George Hadley. The scientist’s first publication 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 Dalton’s works. Dalton dedicated 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, but a person with deuteranopia, as a rule, will not see anything
For half of his life, Dalton had no idea that there was anything wrong with his vision. He studied optics and chemistry, but discovered his defect thanks to his passion for botany. The fact that he could not distinguish a blue flower from a pink one, he attributed to confusion in the classification of flowers, and not to the shortcomings of his own eyesight. He noticed that the flower, which during the day, in the light of the sun, was sky blue (or rather, the color that he considered sky blue), looked dark red in the light of a candle. He turned to those around him, but no one saw such a strange transformation, with the exception of his brother. Thus, Dalton realized that there was something 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”, where he explained the narrowness of color perception of some people by the discoloration of the liquid substance of the eye . Having described this disease using his own example, Dalton drew the attention of people who, until that moment, had not realized that they had it. Although 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" became firmly attached to the disease. 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 violet and blue, he could normally recognize only one color - yellow, and wrote about it this way:
That part of the picture that others call red seems to me like a shadow or simply poorly lit. Orange, green and yellow appear to be shades of the same color, ranging from intense to pale yellow.This work by Dalton was followed by a dozen new ones, devoted to a variety of topics: the color of the sky, the causes of fresh water sources, 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 number of reports under the general title “Experiments”, devoted to determining the composition of gas mixtures, the vapor pressure of various substances at different temperatures in vacuum and in air, the evaporation of liquids, and the thermal expansion of gases . Four such articles were published in the Society's Reports in 1802. Particularly noteworthy is the introduction to Dalton's second work:
There can hardly be any doubt about the possibility of the transition of any gases and their mixtures into a liquid state; you just need to apply appropriate pressure to them or lower the temperature, up to separation into individual components.After describing experiments to establish the vapor pressure of water at various temperatures ranging from 0 to 100 °C, Dalton proceeds 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 don’t see any objective reasons to consider incorrect the fact that any two gases (elastic medium) with the same initial pressure expand equally when the temperature changes. However, for any given expansion of mercury vapor (an inelastic medium), the expansion of air will be less. Thus, a general law that would describe the nature of heat and its absolute quantity should be derived from studying the behavior of elastic media. Gas lawsJoseph Louis Gay-Lussac
Thus, Dalton confirmed Gay-Lussac's law, published in 1802. Within two or three years of reading his articles, Dalton published a number of works 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 considered to be those related to the atomistic concept in chemistry, with which his name is most directly associated. It is suggested (by Thomas Thomson) that this theory was developed either from studies of the behavior of ethylene and methane under various conditions, or from the analysis of nitrogen dioxide and monoxide.
A study of Dalton's laboratory notes, discovered in the Lit & Phil archives, suggests that as he searched for an explanation for 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 became stronger in his head, supported by experimental facts obtained from the study of the atmosphere. The first beginnings of this idea to be seen can be found at the very end of his article on the absorption of gases (written October 21, 1803, published in 1805). Dalton writes:
Why doesn't water retain its shape like any gas? Having devoted a lot of time to solving this problem, I cannot give a suitable answer with complete confidence, but I am sure that it all depends on the weight and number of microparticles in the substance. Determination of atomic weightsA list of the chemical symbols of individual elements and their atomic weights, compiled by John Dalton in 1808. Some of the symbols used to represent chemical elements at that time date back to the era of alchemy. This list cannot be considered a "Periodic Table" because it does not contain repeating (periodic) groups of elements. Some of the substances are not chemical elements, for example, lime (position 8 on the left). Dalton calculated the atomic weight of each substance in relation to hydrogen as the lightest, ending his list with mercury, which was mistakenly assigned an atomic weight greater than that of lead (item 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 his research, Dalton after some time published a table of the 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 in his notes dated 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 the scientist believed all gases were 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 simple 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 perfectly confirmed his conclusion. It is worth noting that the law of multiple ratios was predicted 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 with twice the same, but there cannot be any intermediate values of the amount of substance." It is believed that this sentence was added some time after the report was read, but it was not published until 1805.
In his work “New Course in 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, combining with one atom of element Y, gives a double compound. If one atom of element X combines with two Y (or vice versa), then such a connection will be triple.
Five basic principles of Dalton's theory The atoms of any element are different from all others, and the 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, or destroyed through 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 the “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.
This was only an assumption received by the scientist simply from faith 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, since the calculation of relative atomic weights is impossible without knowledge of the chemical formulas of compounds. However, Dalton's hypothesis led him to determine the formula of water as OH (since, from the standpoint of his theory, water is a product of the H + O reaction, 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 at the very heart of Dalton's concept, some of its principles have survived to this day, albeit with minor reservations. Let's say that atoms really cannot be divided into parts, created or destroyed, but this is only true for chemical reactions. Dalton also did not know about the existence of isotopes of chemical elements, the properties of which sometimes differ 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 in 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 remaining unpublished material 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, making 116 reports, of which the earliest are the 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 considered one of the weakest) was considered unworthy of publication by the Royal Society, forcing Dalton 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 of 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; accordingly, as the scientist wrote, they occupy certain “pores” in the structure of water.
James Prescott Joule - Dalton's famous student.
Dalton's experimental method
Sir Humphry 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 “rude experimenter” who always found the facts he needed, more often taking them from his head than from real experimental conditions. On the other hand, historians who were directly involved with 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 misled him so often 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 accepted things. For example, Dalton criticized and, it seems, never fully accepted the Gay-Lussac gas law. The scientist adhered to unconventional views on the nature of chlorine even after G. Davy established its composition; 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 heritage. - London, 1917)
Even before the creation of his atomistic concept, Dalton was widely known in scientific circles. In 1804 he was offered to give a course of lectures on natural philosophy at the Royal Institution (London), where he then read another course in 1809-1810. Some of Dalton's contemporaries questioned his ability to present material in an interesting and beautiful manner; John Dalton had a rough, quiet, inexpressive voice; in addition, the scientist explained even the simplest things too complicated.
In 1810, Sir Humphry Davy invited him to stand for election to the Royal Society, but Dalton refused, apparently due to financial difficulties. In 1822, he found himself a candidate without knowing it, and after the elections he paid the required fee. Six years before this event, he became a corresponding member of the French Academy of Sciences, and in 1830 he was elected one of the eight foreign members of the academy (in place of Davy).
In 1833, the government of Earl Gray assigned him a salary of 150 pounds, in 1836 it increased to 300.
Dalton never married and had few friends. He lived for a quarter of a century with his friend R. W. Jones (1771-1845) in George's Street, Manchester; his usual routine 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 congresses of the British Association in York, Oxford, Dublin and Bristol.
End of life, legacy
Passepartout by Dalton (circa 1840).
Bust of Dalton by the English sculptor Chantray
In 1837, Dalton suffered a mild heart attack, but already in 1838 the next blow caused him speech impairment; 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 Manchester apartment.
John Dalton was buried in Ardwick Cemetery, Manchester. Nowadays there is a playground on the site of the cemetery, but photographs of it have survived. A bust of Dalton (by Chantray) adorns the entrance to King's College Manchester, and a statue of Dalton, also by Chantray, is 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 designate a unit of atomic mass of an element (equivalent to 1/12 the mass of 12C). Also named after the scientist is the street connecting Deansgate and Albert Square in the center of Manchester.
One of the buildings on the campus 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 from the building there is a statue of Dalton, moved here from London (the work of William Teed, 1855, until 1966 it stood on Piccadilly Square).
The University of Manchester student residence building also bears Dalton's name. The university has established various grants named after Dalton: two in chemistry, two in mathematics, and the Dalton Prize in natural history. There is also the Dalton Medal, awarded periodically by the Manchester Literary and Philosophical Society (a total of 12 medals were issued).
There is a crater on the Moon named after him.
Much of John Dalton's work was destroyed in the bombing of Manchester on December 24, 1940. Isaac Asimov wrote about this: “In war, not only the living die.”
The basis of every theory in natural science
there is always something that cannot
be confirmed experimentally.
I. Ya. Berzelius
How does D. Dalton’s atomic theory differ from previous versions of atomism? What influence did Dalton's work have on the subsequent development of natural science? What new did Dalton's atomism contribute to the understanding of the genesis of the properties of substances?
Lesson-lecture
THE STUDY ABOUT THE COMPOSITION OF SUBSTANCES. Historically, it so happened that the doctrine of elements and atomistic ideas until the beginning of the 19th century. were considered as fundamentally different ways of explaining the structure and properties of bodies. Properties were often explained by the presence in the body of certain elementary principles, the role of which could be played by the elements of Aristotle (fire, water, air, earth), the three principles of Paracelsus (mercury, sulfur, salt) or any other sets of elementary essences. Proponents of atomistic ideas associated properties with the geometric and mechanical characteristics of the particles that make up the body (for example, with their size, shape, movement, with their inherent forces).
Lavoisier's idea about the existence in nature of a finite number of elements that have a certain set of properties and can be determined by methods of chemical analysis contributed to the subsequent synthesis of atomism and the study of elements.
But in order for these two teachings to merge into one, the atomic theory had to be modified. And the main thing that had to be done was to find a property of the atom that, on the one hand, would remain unchanged during chemical reactions and aggregate transitions, and on the other, would be amenable to quantitative experimental determination. Neither the shape nor the size of the atoms were suitable for this role, if only because they could not be determined experimentally. As a suitable property of the atom, D. Dalton chose relative atomic weight (the term is currently used relative atomic mass, or simply “atomic mass”).
John Dalton (1766-1844) - English physicist and chemist. Worked in the fields of meteorology and gas physics, described the vision defect known as color blindness
DALTON'S THEORY. It all started with meteorology, which Dalton studied throughout his adult life, making about 200,000 records of weather conditions. In the process of meteorological observations, he became interested in the properties of gases and gas mixtures, and when discussing certain issues of the physics of gases, he used atomic theories, which were very common in England since the 17th century. As a result, by 1801 he had developed the following ideas about the nature of the gaseous state:
- gas atoms are surrounded by a thermogenic shell, the volume of which increases with increasing temperature;
- between gas particles there are repulsive forces caused by the repulsion of caloric shells, and attractive forces (“chemical affinity”);
- gas particles are located in space so densely that the caloric shells touch each other (Fig. 55).
Rice. 55. Dalton gas model
To answer a number of important questions (why gas diffusion occurs; why the atmosphere does not stratify, i.e., why heavy gases do not accumulate near the Earth’s surface, etc.), it was necessary first of all to learn how to determine the composition of the gas mixture; for a start - at least the amount of oxygen in it: without this it was impossible to experimentally study the change in the composition of the atmosphere with altitude, the solubility of gases in water and other problems. The fastest way to determine oxygen in a gas mixture, according to Dalton, could be the so-called Priestley test, i.e., reactions that in modern notation have the form:
2NO + O 2 → 2NO 2 or in the presence of water:
2NO + O 2 + H 2 O → HNO 2 + HNO 3
As a result, Dalton came to the need to determine the composition of nitrogen oxides, and for this it was necessary to know the relative atomic masses of nitrogen and oxygen. Thus, it was in the process of solving the chemical problem of the composition of nitrogen oxides that the problem of determining relative atomic masses arose. However, in order to create a scale of relative atomic masses (Dalton took the mass of a hydrogen atom as one), it was necessary to know the atomic compositions of compounds - how many atoms of each element are included in the molecule (“complex atom”, in Dalton’s terminology) of a given compound, and in order to determine atomic composition of a compound, you need to know its elemental composition (in percent by mass) and... the relative atomic masses of the atoms of the elements included in the compound. The circle is closed.
To somehow get out of this situation, Dalton came up with a rule that he called the “rule of simplicity.” He just came up with it, because he couldn’t give any more or less compelling arguments to prove this rule, only speculative ones, like “nature always acts in the simplest way,” “you shouldn’t increase complexity unnecessarily,” etc.
Chemical symbols of D. Dalton. 1810
According to this rule, if two elements form only one compound (as, for example, hydrogen and oxygen give only water; hydrogen peroxide had not yet been discovered), then its composition will be the simplest: AB, i.e. water in this case should have the composition of HO, ammonia NH, etc. As we see, Dalton did not “guess” the composition of water and ammonia, and therefore his numerical scale of relative atomic masses turned out to be incorrect.
But the imperfections of Dalton's theory do not detract from the breakthrough he made. Dalton proceeded in his reasoning from the fact that an element is atoms of the same type, with certain atomic weights, and each atom is an atom of a certain chemical element. In other words, the atoms of various chemical elements are not identical in their properties and in their masses, while all atoms of the same substance are completely identical.
In addition, Dalton showed that the atomic theory he proposed could be not only speculative, but also a working theory: the problem of the genesis of the properties of substances can and should be associated with the atomic composition of bodies.
Atomistic ideas and ideas about the elements, having undergone a long historical evolution, finally united into one fundamental teaching.
- In his calculations of the relative atomic masses of nitrogen and oxygen, Dalton proceeded from those known at the beginning of the 19th century. data on the percentage (by mass) composition of water (85% oxygen and 15% hydrogen) and ammonia (80% nitrogen and 20% hydrogen). Based on these data and Dalton’s principle of simplicity, determine the values he obtained for the relative masses of nitrogen and oxygen (Dalton took the atomic mass of hydrogen as 1).
- At first, Dalton believed that one of the nitrogen oxides, the so-called saltpeteric acid, had an atomic composition that in modern notation can be represented by the formula NO 2. The percentage (by weight) composition of this oxide, according to data of that time, was as follows: 29.5% nitrogen and 70.5% oxygen. By comparing the hypothetical atomic and experimentally determined percentage compositions of this oxide and using his scale of relative atomic masses (see the previous problem), Dalton proposed a new formula for ammonium nitrate. Which one? Justify your answer with calculations.
- How can one interpret the law of constancy of composition from the standpoint of Dalton's atomic theory?
- Why did Dalton call his two-volume work, published in 1808-1810, “A New System of Chemical Philosophy”?
- What provisions of Dalton's atomic theory, in your opinion, caused the greatest objections among his contemporaries?
DALTON John (Dalton J.)
(6.IX.1766 - 27.VII.1844)
John Dalton Born into a poor family, he had great modesty and an extraordinary thirst for knowledge. He did not hold any important university position, but 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 symbols for simple and complex substances.
John Dalton - English chemist and physicist, member of the Royal Society of London (since 1822). Born in Eaglesfield (Cumberland). I received my education on my own.
In 1781-1793 - teacher of mathematics at a school in Kendal, from 1793 he taught physics and mathematics at New College in Manchester.
Basic scientific research before 1800-1803. belong to physics, later ones - to chemistry.
Conducted (since 1787) meteorological observations, studied 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 blindness.
Opened three laws, which formed the essence of his physical atomism of gas mixtures: partial pressures gases (1801), dependencies volume of gases at constant pressure on temperature(1802, independent of J.L. Gay-Lussac) and dependence solubility gases from their partial pressures(1803) These works led him to the solution of the chemical problem of the relationship between the composition and structure of substances.
Proposed and substantiated (1803-1804) theory of atomic structure, or chemical atomism, which explained the empirical law of constancy of composition.
Theoretically predicted and discovered (1803) law of multiples: if two elements form several compounds, then the masses of one element per the same mass of the other are related as whole numbers.
Compiled (1803) the first table of relative atomic masses hydrogen, nitrogen, carbon, sulfur and phosphorus, taking the atomic mass of hydrogen as unity.
Proposed (1804) system of chemical signs for "simple" and "complex" atoms.
He carried out (since 1808) work aimed at clarifying certain provisions and explaining the essence of the atomic theory.
Member of many academies of sciences and scientific societies.
The first scientist who achieved significant success in the new direction of development of chemistry was the English chemist John Dalton (1766-1844), whose name is closely associated with atomic theory. At the beginning of the 19th century, Dalton discovered several new experimental principles: law of partial pressures(Dalton's law), law of solubility of gases in liquids(Henry-Dalton law) and finally law of multiples. It is impossible to explain these patterns (primarily the law of multiple ratios) without resorting to the assumption that matter is discrete. Based on the law of multiple ratios, discovered in 1803, and the law of constancy of composition, Dalton developed his atomic-molecular theory, outlined in his work “A New System of Chemical Philosophy,” published in 1808.
The main provisions of Dalton's theory are as follows:
1. All substances consist of a large number of atoms (simple or complex).
2. Atoms of the same substance are completely identical. Simple atoms are absolutely immutable and indivisible.
3. Atoms of different elements are able to combine with each other in certain proportions.
4. The most important property of atoms is atomic weight.
Already in 1803, the first table of relative atomic weights of certain elements and compounds appeared in Dalton's laboratory journal; As a reference point, Dalton chooses the atomic weight of hydrogen, taken equal to unity. To designate the atoms of elements, Dalton uses symbols in the form of circles with various figures inside. Subsequently, Dalton repeatedly corrected the atomic weights of elements, but for most elements he gave incorrect values of atomic weights.
Dalton was forced to make the assumption that atoms of different elements join together in the formation of complex atoms. "the 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 (a 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 underestimated value of the atomic weight of oxygen, which leads, in turn, to incorrect determination of the atomic weights of metals based on the composition of the oxides. The principle of greatest simplicity (supported by the authority of Dalton as the creator of the atomic-molecular theory) subsequently played a certain negative role in solving the problem of atomic weights. However, in general, Dalton's atomic theory formed the basis for all further development of natural science.
DALTON, John
English physicist and chemist John Dalton was born in the village of Eaglesfield in Cambeoland into a weaver's family. He received his education on his own, except for the lessons in mathematics that he took from the blind teacher J. Gauff. In 1781–1793 Dalton taught mathematics at a school in Kendal, and from 1793 - physics and mathematics at New College in Manchester. Dalton's scientific work began in 1787 with observations of the air. Over the next 57 years, he kept a meteorological diary in which he recorded more than 200,000 observations. During his annual trips around the Lake District, Dalton climbed the peaks of Skiddaw and Helvellyn to measure atmospheric pressure and take air samples.
In 1793, Dalton published his first work, Meteorological Observations and Sketches, which contained the beginnings of his future discoveries. Trying to understand why gases in the atmosphere form a mixture with certain physical properties, and are not located one above the other in layers in accordance with their densities, he established that the behavior of the gas does not depend on the composition of the mixture. Dalton formulated the law of partial pressures of gases, and also discovered the dependence of the solubility of gases on their partial pressure. In 1802, Dalton independently, independently of J. L. Gay-Lussac and J. Charles, discovered one of the gas laws: at constant pressure, with increasing temperature, all gases expand equally.
Studying the compositions of chemical compounds, Dalton established that in various compounds of two elements, for the same amount of one element there are amounts of the other, related to each other as simple integers (the law of multiple ratios). Dalton tried to explain the discovered laws using the atomistic concepts he developed. Dalton introduced the concept of atomic weight as the most important property of the atom. Taking the atomic weight of hydrogen as one, Dalton calculated the atomic weights of a number of elements and compiled the first table of relative atomic masses (1803).
Dalton considered chemical reactions as processes of connection and separation of atoms connected with each other, because only this could explain the abrupt changes in composition when converting one compound into another. Therefore, each atom of any element must, in addition to a certain mass, have specific properties and be indivisible from a chemical point of view.
Dalton's calculations of atomic masses were inaccurate because he did not distinguish between atoms and molecules, calling the latter complex atoms. Nevertheless, it was thanks to Dalton that atomism received a new natural scientific basis; Dalton's work became a major milestone in the development of chemical science. In 1804, Dalton also proposed a system of chemical symbols for “simple” and “complex” atoms. Dalton's name is given to a visual defect - color blindness, from which he himself suffered and which he described in 1794.
In 1816 Dalton was elected a member of the French Academy of Sciences, chairman of the Manchester Literary and Philosophical Society, and in 1822 a member of the Royal Society of London. In 1832, Oxford University awarded him the degree of Doctor of Laws.
