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MOST IMPORTANT SCIENTIFIC DISCOVERIES
Discovery of oxygen. History and essence of scientific discovery
Directory / The most important scientific discoveries All this ancient information was gradually forgotten. Only in the XNUMXth century did the great Leonardo da Vinci mention oxygen in passing. It was rediscovered in the 1620th century by the Dutchman Drebbel. Very little is known about him. He was probably a great inventor and a great scientist. He managed to create a submarine. However, the volume of the boat is limited, so taking air, consisting mainly of nitrogen, was unprofitable. It makes more sense to use oxygen. And Drebbel gets it from saltpeter! This happened in XNUMX, more than one hundred and fifty years before the "official" discovery of oxygen by Priestley and Scheele. Joseph Priestley (1733–1804) was born in Fieldhead, Yorkshire, the son of a poor cloth maker. Priestley studied theology and even preached to a Protestant community independent of the Anglican Church. This allowed him to further receive a higher theological education at the Academy in Deventry. There, Priestley, in addition to theology, was engaged in philosophy, natural science, studied nine languages. So when, in 1761, Priestley was accused of freethinking and banned from preaching, he became a teacher of languages at Warrington University. It was there that Priestley took his first chemistry course. This science made such a great impression on Priestley that, at the age of thirty, being a man of a certain position, he decided to start studying natural science and conducting chemical experiments. At the suggestion of Benjamin Franklin, Priestley in 1767 wrote a monograph "History of the doctrine of electricity." For this work, he was elected an honorary doctor of the University of Edinburgh, and later a member of the Royal Society of London (1767) and a foreign honorary member of the St. Petersburg Academy of Sciences (1780). From 1774 to 1799, Priestley discovered or first obtained in pure form seven gaseous compounds: nitrous oxide, hydrogen chloride, ammonia, silicon fluoride, sulfur dioxide, carbon monoxide and oxygen. Priestley was able to isolate and study these gases in a pure state, because he significantly improved the previous laboratory equipment for collecting gases. Instead of water in a pneumatic bath, proposed earlier by the English scientist Stephen Gales (1727), Priestley began to use mercury. Priestley, independently of Scheele, discovered oxygen by observing the evolution of gas when a solid substance under a glass jar is heated without access to air, using a strong biconvex lens. In 1774, Priestley conducted experiments with mercury oxide and minium. He dipped a small test tube with a small amount of red powder into mercury and heated the substance from above with a biconvex lens. Priestley subsequently outlined his experiments on obtaining oxygen by heating mercury oxide in the six-volume work "Experiments and Observations on Different Types of Air". In this work, Priestley wrote: “I took out a lens with a diameter of 2 inches, with a focal length of 20 inches, and began to investigate with its help what kind of air is emitted from a variety of substances, natural and artificially prepared. After I made a series of experiments with this apparatus, I tried on August 1, 1774, to isolate air from calcined mercury and immediately saw that air could very quickly be released from it. I was unspeakably surprised that a candle in this air burns unusually brightly, and I did not know at all how to explain this phenomenon. A smoldering splinter, brought into this air, emitted bright sparks. I have found the same release of air when lead lime and red lead are heated. I tried in vain to find an explanation for this phenomenon ... But nothing that I have done so far has surprised me so much and has not given me such satisfaction. “Why did this discovery cause such surprise in J. Priestley?” asks Yu.I. Solovyov. "dephlogisticated air" from mercury oxide when heated seemed to him simply impossible. That's why he was "so far from understanding what he really got" ... In 1775, he described those properties that distinguish "new air" from "other gas "nitrogen oxide". Having discovered a new gas in August 1774, J. Priestley, however, did not have a clear idea of its true nature: “I frankly admit that at the beginning of the experiments referred to in this part, I was so far from being to form some hypothesis which would lead to the discoveries which I made, which would seem to me incredible if they were told to me." Priestley's research on the chemistry of gases, and especially his discovery of oxygen, prepared the way for the defeat of the theory of phlogiston and outlined new paths for the development of chemistry. Two months after receiving oxygen, Priestley, having arrived in Paris, reported his discovery Lavoisier. The latter immediately realized the enormous significance of Priestley's discovery and used it to create the most general oxygen theory of combustion and to refute the theory of phlogiston. Scheele worked at the same time as Priestley. He wrote about his priorities: “The study of air is currently the most important subject of chemistry. This elastic fluid has many special properties, the study of which contributes to new discoveries. The amazing fire, this product of chemistry, shows us that without air it cannot be produced .. ." Carl Wilhelm Scheele (1742-1786) was born in the Swedish city of Stralsund to a family of a brewer and grain merchant. Karl studied in Stralsund at a private school, but already in 1757 he moved to Gothenburg. Scheele's parents did not have the means to give a higher education to Karl, who was already the seventh son in this large family. Therefore, he was forced to become first a pharmacist's apprentice, then work his way into science by many years of self-education. Working in a pharmacy, he achieved great skill in chemical experiment. In one of the pharmacies in Gothenburg, Scheele learned the basics of pharmacy and laboratory practice. In addition, he diligently studied the works of chemists I. Kunkel, N. Lemery, G. Stahl, K. Neumann. After working for eight years in Gothenburg, Scheele moved to Malmö, where he very soon showed remarkable experimental abilities. There he was able to do his own research in the evenings in the pharmacist's laboratory, where he prepared medicines during the day. At the end of April 1768, Scheele moved to Stockholm, hoping to establish close contacts with scientists in the capital and get a new incentive to carry out work. However, Scheele did not have to conduct chemical experiments in the Korpen pharmacy in Stockholm; he was engaged only in the preparation of medicines. And only sometimes, sitting somewhere on a cramped windowsill, did he manage to conduct his own experiments. But even in such conditions, Scheele made a number of discoveries. So, for example, studying the effect of sunlight on silver chloride, Scheele found that the darkening of the latter begins in the violet part of the spectrum and is most pronounced there. Two years later, Scheele moved to Uppsala, where such famous scientists as the botanist Carl Linnaeus and chemist Thorburn Bergman. Scheele and Bergman soon became friends, which greatly contributed to the success in the scientific activities of both chemists. Scheele was one of those scientists who were lucky in their work. His experimental research contributed significantly to the transformation of chemistry into a science. He discovered oxygen, chlorine, manganese, barium, molybdenum, tungsten, organic acids (tartaric, citric, oxalic, lactic), sulfuric anhydride, hydrogen sulfide, hydrofluoric and hydrofluorosilicic acids, and many other compounds. He was the first to obtain gaseous ammonia and hydrogen chloride. Scheele also showed that iron, copper, and mercury had different oxidation states. He isolated a substance from fats, later called glycerol (propanetriol). Scheele is credited with obtaining hydrocyanic (hydrocyanic) acid from Prussian blue. Scheele's most significant work, The Chemical Treatise on Air and Fire, contains his experimental work done in 1768-1773. It can be seen from this treatise that Scheele had received and described the properties of "fiery air" (oxygen) somewhat earlier than Priestley. The scientist received oxygen in various ways: by heating saltpeter, magnesium nitrate, by distilling a mixture of saltpeter with sulfuric acid. "Fiery air," wrote Scheele, "is the very one by means of which the circulation of blood and juices in animals and plants is maintained ... I am inclined to think that the "fiery air" consists of an acidic thin matter, combined with phlogiston, and, probably that all acids derived their origin from "fiery air." Scheele explained his results by the assumption that heat is a combination of "fiery air" (oxygen) and phlogiston. Therefore, it is the same as Mv Lomonosov, and G. Cavendish, identified phlogiston with hydrogen and thought that when hydrogen is burned in air (when hydrogen and "fire air" are combined), heat is generated. In 1775 Bergman published an article on Scheele's discovery of "fire air" and his theory. “We have already noted,” Bergman wrote, “the great force with which “clean (fiery) air” removes phlogiston from iron and copper. Nitric acid also has a great affinity for this element ... These phenomena are attributed to the migration of phlogiston from acid to air and are easily explained by the fact that it has been so well proved by the experiments of Herr Scheele that heat is nothing but phlogiston closely combined with pure air, in the combination of which the resulting body is generated (and there is a decrease in the volume previously occupied). Although it is commonly said that Scheele was about two years late in publishing his paper on Priestley, Bergman reported Scheele's discovery of oxygen at least three months before Priestley's. Here is an excerpt from Bergman's preface to Scheele's book: "Chemistry teaches that the elastic medium that surrounds the Earth, at all times and in all places, has a single composition, including three different substances, namely good air (oxygen - Approx. auth.), Spoiled "mephitic air" (nitrogen - Approx. auth.) and essential acid (carbon dioxide - ed.) The first Priestley called, not only incorrectly, but with a stretch, "dephlogisticated air", Scheele - "fiery air", since he alone supports the fire, while while the other two put it out... I repeated, with various modifications, the basic experiments on which he (Scheele) based his conclusions, and found them to be perfectly correct.Heat, fire, and light have basically the same constituent elements: good air and phlogiston... Of the kinds of substances now known, good air is the most effective in removing phlogiston, which seems to be a real elemental substance found in many matters.Therefore, I placed good air above phlogiston, in my new table of affinity... In conclusion, I must say that this wonderful work was completed two years ago, despite the fact that, for various reasons, which it is superfluous to mention here, it has only now been published. It therefore happened that Priestley, not knowing Scheele's work, had previously described various new properties relating to air. However, we see that they are of a different kind and presented in a different connection. Author: Samin D.K.
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