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Founder of the Chemical Atomism. To the 250th anniversary since the birth of John Dalton


Джон Дальтон

The 6th of September, 2016 it has been 250 years since the birth of famous English scientist John Dalton.

He was a member of the Royal Society, a foreign member of the French Academy of Science, the President The Manchester Literary and Philosophical Society, an honored doctor in Oxford and Edinburgh universities.

Nowadays, many scientific terms have been named after him: Dalton’s chemical atomism, Dalton’s law of gas, measurement unit of weight of atoms, molecules and viruses – Dalton(Da), daltonides – chemicals of constant proportions, daltonism or color vision deficiency.

Life

In the beginning of John Dalton’s life there were no reasons to attain worldwide fame. He was born the 6th of September in 1766 in the family of a poor weaver in the village Eaglesfield in the north of England. Father taught him to read and gave basic knowledge in the Math. When he was 10, he started attending school in Pardshow-hall which was 3 km from home and there he turned out to have brilliant skills in the Math. After studying for 2 years he began to teach (as well as make a living) at the age of 12 in the Eaglesfield school. In 2 years he had to quit and work in the farm for a year. Since 1781 he had been a teacher in Kendall for 12 years. At the same time he learned Latin, Math and “natural philosophy”- mostly Physics. During that period he began to work with “Calendar for gentlemen and ladies” , therefore in 1787 he started meteorological observations which he continued to do during the whole life. The result of 5 years’ observations he put in the book “Meteorological observations and researches” which was published in 1793.

During scientific lessons Dalton got acquainted with John Hogue who helped him get a job as a professor of Math and Physics in 1793 in the New College - institution of higher education in Manchester. After a while Dalton befriended with 23-years old Robert Owen – future famous public figure in England who recommended John for membership in Manchester Literary and Philosophical Society. A few weeks later Dalton made a report and published his article in the collection society’s collection. In that article defect of vision was described for the first time. John noticed in himself and his brother this defect – inability to differentiate colors. Afterwards this defect was called daltonism.

In 1794-1800 Dalton was making researches, reports and speeches at the society’s sessions and publishing articles about meteorological phenomena such as rain, dew, fog and about some issues in English grammar.

In 1800 the New College moved from Manchester to York, but Dalton stayed in Manchester to continue teaching activities. In 1801 he was chosen to be the secretary of Manchester Literary and Philosophical Society.

The same year the most productive period of John’s research began. In 1801 he formulated the law: the pressure of gas mixture equals the sum of their partial pressures(Dalton’s law). In 1802 h e discovered the law of thermal expansion of gases at constant pressure which is now known as Gay-Lussac's law ( although Gay-Lussac discovered this law several months after Dalton).

In 1803 Dalton first version of “table of relative weights of primary particles” which appeared to be the first step on the way to his atomic theory. In 1804 he told an authoritative chemist Tomas Tomson who was the author of the manual “The system of chemistry” about his theory .With Dalton’s agreement Tomson included his theory in the third edition of his book. This action advanced the establishment of the theory among the scientists. The next year the first part of first tome of Dalton’s book “ New system of chemical philosophy” with detailed description and experimental basis of the theory was published. The second part was published in 1810 and the second tome in 1827.

In 1816 Dalton was chosen to be a foreign member of the French Academy of Science. The next year he became the president of The Manchester Literary and Philosophical Society. In 1822 he went on a trip to France where he met French scientists including C. Berthollet and J.Gay-Lussac.The same year he was chosen in members of the Royal Society.

Dalton continued his experimental and theoretical researches and teaching as well. It is interesting to point out that in 1834- 1837 he gave lessons in Math and Physics to the future famous physician John Joule and his brother.

In 1837 he suffered an infarction and became partially paralyzed. The 27th of July he died from the second infarction in Manchester.

THE BEGINING OF THE CHEMICAL ATOMISTYC CREATION

The main John Dalton"s achivement as a scientist was the creation of chemical atomistyc concept, according to which a substance consists of indivisible atoms in chemical process; simple substancesconsist of one kind of atoms,and the smallest shares of compound substances consist of different atoms.

The way to that invention was very difficult. The most difficult, accordingly, the most interesting, was the first step. To tell about this first step is worth more,because a lot of books give its erroneus description. They are confirm, that Dalton, based on given of quantitative substances" analysis, formulated the law of кратный не знаю как, relations [ if two elements which react to each other, they develop some combinations,then different mass quantity of one element,which connect with the same mass quantity of another, refer as not big целые,не знаю и нет в словаре numbers} he explained this law,putting forward a hypothesis about atom"s existence. In reallity that was the other way round. According to his hypothesis about existence of named кратных тоже нет в словаре relations, for control it he began to analyse the facts of quantity substances" analyse. As for substances" chemical construction, he payed attention when he solved questions connected with meteorology.

First of all, it should be noted that at the beginning of XIX century gases were considered to be elastic fluid. Gases’ particles were considered to join one to another and different gases as well as fluids were considered to dissolve one in another due to existence of force of gravity (affinity) between their parts. Moreover, state of saturated water vapor in the air was believed to emerge because of the same reason the brine in water: the solvent saturates and stops absorbing the substance which dissolves.

Researching atmosphere air, Dalton identified that the amount of “dissolved” steam in closed container is determined only by temperature and doesn’t depend on the amount(pressure) of air in it. Moreover, the amount of vapor will be the same if the air from the container is discharged. That implied that the reason of evaporation isn’t about chemical affinity between steam and air. Then what is the reason? Dalton suggested that gases dissolved one in another not due to attraction of their atoms, but due to existence of repulsive force between atoms of one of the gases. Also he suggested that one gas’ atoms don’t influence on the other gas’ atoms: every gas is emptiness for another. It followed the conclusion that now is called Dalton’s law: the pressure of gas mixture equals the sum of their partial pressures.

The suggestion about existence of so many repulsive forces ,however, seemed unreal and was criticized by French and English chemists. Dalton listened to critics and started thinking how to get rid of suggestion about variety of repulsive forces. In 1803 it came to his mind that v of atoms was caused by the influence of weightless fluid of Caloric which creates membrane around gas’ atoms. Then why is one gas emptiness for another ? Dalton decided that it can be explained, provided that the atoms’ sizes of different gases are different and the process of mixing the gases is like pouring of small balls through big ones.

To prove this hypothesis, Dalton began to search for a way to fix the atom"s size.Thinking the atoms of gas connect with each other, the volume of atom can be estimated deviding the volume of gas into its quantity,and knowing the atom"s volume and supposing it has spherical shape, it is easy to discover its diameter. General number of atoms can be find, if you know the weigh of gas and atom. It is impossible to weigh atom. But you can find its relative weigh,if you will take a weigh of any atom.Dalton took the weight of hydrogen as the smallest, and using well known facts about the per cent composition of chemical combinations, on the sixth of September in 1803 he had put together the first list of relative weights of primary componants. On the 19 of September he had put together the list where he wrote the specific weight of gas,relative weight of gas atoms and their diameters. Since he had known that two elements{ for example, nitrogen and oxygen create not only one combination, he supposed, that parts of chemical compound gases can consist of two,three and more atoms. In this case he concludes, the weight of one element, which takes to unit of others weight, in different combinations will difer as not big numbers.

There were experiments calculations discussions. But the decisive step to the chemical atomistyc had been done.

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