Argon in cylinders in Kazakhstan
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atomic number 18;
atomic mass 39,948.
temperature of boiling 77,35 K with a pressure of 101,3 kPa
specific volume is 1,239 dm3/kg at a temperature of 77,35 To and pressure of 101,3 kPa.
Argon — an element of the main subgroup of the eighth group, the third period of the Periodic Table of D. I. Mendeleyev, with atomic number 18. Argon is designated by an Ar symbol (Latin). An element, the third on prevalence, in the terrestrial atmosphere (after nitrogen and oxygen) — 0,93% on volume. Simple substance argon (CAS number: 7440-37-1) — inert one-nuclear gas without color, taste and a smell.
History of discovery of argon begins in 1785 when the English physicist and the chemist Henry Cavendish, studying composition of air, decided to establish whether all nitrogen of air is oxidized. Within many weeks it subjected to influence of an electric discharge air mix with oxygen in U-shaped tubes therefore in them all new portions of brown nitrogen oxides which the researcher periodically dissolved in alkali were formed. After a while formation of oxides stopped, but after binding of the remained oxygen there was a vial of gas which volume did not decrease at long influence of electric discharges in the presence of oxygen. Cavendish estimated the volume of the remained gas bubble in 1/120 from the initial volume of air [4][5][6]. Cavendish could not solve a bubble riddle therefore he stopped the research, and did not even publish its results. Only many years later the English physicist James Maxwell collected and published unpublished manuscripts and laboratory notes of Cavendish.
Further history of discovery of argon is connected with a name of the Rayleigh which devoted several years to researches of density of gases, especially nitrogen. It turned out that the liter of the nitrogen received from air weighed more than a liter of the "chemical" nitrogen (received by decomposition of any nitrogenous compound, for example, of nitrous oxide, oxides of nitrogen, ammonia, urea or saltpeter) on 1,6 mg (the weight of the first was equal 1,2521, and the second 1,2505 g). This difference was not so small that it was possible to charge to it an experience error. Besides it constantly repeated irrespective of a source of receiving chemical nitrogen [4].
Without having come to a solution, in the fall of 1892 Rayleigh published the letter to scientists in the Nature magazine, with a request to offer an explanation for that fact that depending on a way of release of nitrogen he received different sizes of density. The letter was read by many scientists, however nobody was able to answer the question [4][5] raised in it.
The English chemist William Ramzaya famous already at that time also had no ready answer, but he offered Rayleigh the cooperation. The intuition induced Ramzaya to assume that nitrogen of air contains impurity of unknown and heavier gas, and the Dewar paid Rayleigh's attention to the description of ancient experiences of Cavendish (which already were published by this time) [5].
Trying to allocate the hidden component from air, each of scientists went in the way. Rayleigh repeated Cavendish's experiment in the increased scale and at higher technological level. The transformer energized sent 6000 volts to a 50-liter bell filled with nitrogen, a sheaf of electric sparks. The special turbine created the fountain of the splashes of solution of alkali absorbing oxides of nitrogen and impurity of carbonic acid in a bell. The remained gas dried up the Rayleigh, and passed through a porcelain tube with the heated copper sawdust detaining the oxygen remains. Experience lasted several days [4].
Ramzay used the ability of heated metal magnesium opened for them to absorb nitrogen, forming solid nitride of magnesium. Repeatedly it missed several liters of nitrogen via the device assembled by it. In 10 days the volume of gas ceased to decrease, therefore, all nitrogen was connected. At the same time by connection with copper the oxygen which was present at quality of impurity to nitrogen was removed. This way Ramzayu in the first experience was succeeded to allocate about 100 cm ³ new gas [4].
So, the new element was open. It became known that it is heavier than nitrogen almost by one and a half times and makes 1/80 part of volume of air. Ramzay by means of acoustic measurements found that the molecule of new gas consists of one atom — before similar gases in a steady state did not meet. From here very important conclusion — time a molecule of an odnoatomn, obviously followed, new gas represents not a difficult chemical compound, but simple substance [4].
A lot of time was spent by Ramzay and Rayleigh for studying of its reactionary ability in relation to many chemically active agents. But, as one would expect, came to a conclusion: their gas is not active at all. It was embarrassingly — till that time any so inert substance [4] was not known.
The big role in studying of new gas was played by the spectral analysis. The range of the gas emitted from air with its characteristic orange, blue and green lines differed from ranges of already known gases markedly. William Kruks, one of the most visible spektroskopist of that time, counted nearly 200 lines in its range. The level of development of the spectral analysis for that time did not give the chance to define, one or several elements possessed an observed range. Several years later it became clear that Ramzay and Rayleigh held in the hand not one stranger, but several — the whole galaxy of inert gases [4].
On August 7, 1894 in Oxford, at meeting of the British association of physicists, chemists and scientists, the message on opening of a new element which was called argon was made. In the report Rayleigh claimed that at each cubic meter of air there are about 15 g of the opened gas (1,288 weight. %) [4][5]. The fact that several generations of scientists did not notice a component of air moreover and in number of the whole percent was too improbable! In few days tens of scientists from the different countries checked experiences of Ramzaya and Rayleigh. There was no doubt left: air contains argon [4].
In 10 years, in 1904, Rayleigh for researches of density of the most widespread gases and discovery of argon gets the Nobel Prize on physics, and Ramzay for opening in the atmosphere of various inert gases — the Nobel Prize in chemistry [4].
Name origin [to govern | to edit the viki-text]
According to the proposal of the doctor of Medan (the chairman of a meeting at which the report on opening was given) Rayleigh and Ramzay named new argon gas (from other - Greek — lazy, slow, inactive). This name underlined the most important property of an element — its chemical inactivity [4].