Muraviikha secondary school

« Amazing story discoveries of oxygen

was born on December 9, 1742 in Stralsund (Pomerania), which then belonged to the Kingdom of Sweden, in the family of a small merchant. As a child, he attended a private boarding school, studied at the gymnasium. Entering an apprenticeship at the Bauch pharmacy in Gothenburg (1756), he mastered the basics of pharmacy and laboratory practice, diligently studied (mainly at night) the works of chemists I. Kunkel, N. Lemery, G. Stahl. The teaching, according to the customs of that time, was to last about ten years. Karl Scheele successfully passed the exams six years later and received the title of pharmacist. Having perfectly mastered the profession and, having moved to Stockholm, Scheele proceeds to independent scientific research. He worked in pharmacies in Stockholm, Uppsala, Köping.
The works and discoveries of Scheele cover all the chemistry of that time: the doctrine of gases, chemical analysis, the chemistry of minerals, the beginnings of organic chemistry (which has not yet emerged as an independent science).
Scheele was the first to obtain and study potassium permanganate KMnO4 - the well-known "potassium permanganate", which is now widely used in chemical experiments and in medicine, developed a method for obtaining phosphorus P from bones, and discovered hydrogen sulfide H2S. The most significant work of Karl Wilhelm Scheele is the Chemical Treatise on Air and Fire, 1777. This book contains the results of his numerous experiments. for the study of gases and combustion processes. It can be seen from the Treatise that Scheele - independently of Priestley and Lavoisier and two years before them - discovered oxygen and described its properties in detail. At the same time, oxygen was obtained by him in many ways: by calcining mercury oxide (as Priestley and Lavoisier did), by heating mercury carbonate and silver carbonate, etc. Undoubtedly, Scheele was the first (1772) to "handle" pure oxygen.

How it was? While living in Uppsala, Scheele began to study the nature of fire, and he soon had to think about what part the air takes in combustion.
Air was then considered an element - a homogeneous substance that cannot be split into even simpler constituent parts by any force. Scheele, too, was of the same opinion at first. But soon he changed it, as he began to conduct experiments with various chemicals in vessels tightly closed on all sides. Whatever substances Scheele tried to burn in closed vessels, he always found the same curious phenomenon: the air that was in the vessel was necessarily reduced by one-fifth during combustion, and at the end of the experiment, water necessarily filled one-fifth of the volume of the flask, which is clearly seen in the figure below from Scheele's manuscript. And he was struck by the idea that the air is not homogeneous.

.

Then he began to study the decomposition by heating of many substances (among which was KNO3 saltpeter) and received a gas that supported breathing and combustion.
Karl Scheele wanted to solve the mystery of fire and at the same time unexpectedly discovered that air is not an element, but a mixture of two gases, which he called air "fiery" and air "unfit". This was the greatest of all Scheele's discoveries.
Scheele manuscript page
But in reality, the mystery of fire and the "fiery" air he received remained a mystery to him. The phlogiston theory prevailing at that time was to blame for everything, according to which it was believed that any substance can burn only if it contains a lot of special combustible matter - phlogiston, and combustion is the decay of a complex combustible substance into a special fiery element - phlogiston - and other components. Karl Scheele was also a supporter of this theory, so he explained that “fiery air” has a great affinity (attraction) for phlogiston, which is why it burns out in it so quickly, and “unusable” air has no attraction for phlogiston, which is why it goes out every fire. It was pretty plausible, but there was one big mystery that seemed completely inexplicable. Where did the “fiery” air go during combustion from a closed vessel during combustion? Finally, he came up with such an explanation. When a body burns, he said, the phlogiston released from it combines with the “fiery” air, and this invisible compound is so volatile that it imperceptibly seeps through glass, like water through a sieve.
Scheele was indeed the first researcher to obtain a relatively pure oxygen sample (1772). However, he published his results in 1777, later than Joseph Priestley did, so he cannot formally be considered the discoverer of oxygen. But in many academic publications and reference books on chemistry, Karl Wilhelm Scheele is given priority. In addition, he has the indisputable priority of discovering the chemical elements chlorine Cl, fluorine F, barium Ba, molybdenum Mo, tungsten W...
Despite the fact that Scheele did not have a higher education and was an ordinary pharmacist, at the age of 32 he was elected a member of the Stockholm Academy of Sciences. He was offered a chair at Uppsala University, a job at the center of the Swedish mining and metallurgical industry in Falun, a chair at the University of Berlin, but the scientist rejected all offers, preferring to do his own experiments.
The second officially recognized contender for the laurels of the discoverer of oxygen is the English priest and chemist Joseph Priestley ().

Priestley Joseph - famous English chemist, philosopher and theologian; manufacturer's son. His amazing ability for languages ​​allowed him to easily learn the languages ​​\u200b\u200bof Arabic, Chaldean, Syriac; without the help of a teacher Priestley learned to speak French, German and Italian. Priestley was mainly engaged in physics and chemistry. While still at school, he independently studied philosophy, logic, and mathematics. The doors of the Royal Academy of Sciences opened for Priestley. After spending some time as a professor of languages ​​at the Washington Academy, Priestley settled in Leeds, where he made his famous studies of carbon dioxide, nitrogen dioxide and oxygen. For these studies, Priestley received the Copley Medal from the Royal Society. The Paris Academy elects Priestley as its member. In 1774, Priestley, heating red mercury oxide, releases oxygen, marveling that a candle burns brightly in this gas. the study of further properties of "dephlogisticated" gas owes much to Priestley. Even from these few examples, Priestley's outstanding powers of observation and experimentation are undeniable. If his discoveries did not have the same success and significance for chemistry as the discoveries of his French contemporary, then this is explained by the fact that Priestley, by the very nature of his scientific thought, belonged to the admirers of the theory of phlogiston, which was already surviving at that time.
On August 1, 1774, Joseph Priestley observed the release of "new air" when heated with a biconvex lens without access to air, mercury scale, located under a glass dome. This solid substance was known to the alchemists under the name "mercurius calcinatus perce", or burnt mercury. In modern chemical language, this substance is called mercury oxide, and the equation for its decomposition when heated is as follows:

mercury oxide

heating

oxygen

Out of curiosity, Priestley introduced a smoldering candle into the collected gas, and it flared up unusually brightly.
One can now imagine how difficult it was to study chemistry at a time when chemical formulas have not yet been invented. What is written in a short chemical equation, Priestley described in 1774 as follows: “I placed under an inverted jar immersed in mercury, a little powder of Mercurius calcinatus perce. Then I took a small burning glass and directed the rays of the Sun directly into the jar onto the powder. Air began to be released from the powder, which forced the mercury out of the jar. I began to study this air. And I was surprised, even excited to the depths of my soul, that in this air a candle burns better and brighter than in an ordinary atmosphere.
Of course, such a description of the reaction looks very poetic compared to the usual chemical equation, but, unfortunately, it does not reflect the essence of the chemical reaction that has taken place.
Priestley himself, being, like Scheele, a supporter of the theory of phlogiston, also could not explain the essence of the combustion process; he defended his ideas even after Antoine Lavoisier promulgated a new theory of combustion.
The claims of Joseph Priestley's supporters regarding the discovery of oxygen by this particular scientist were based on his priority in obtaining gas, which was later recognized as a special, hitherto unknown type of gas. But Priestley's gas sample was not clean. Besides, if Priestley was the discoverer, then when was the discovery made? In 1774, he believed that he had obtained nitrous oxide, that is, a kind of gas that he already knew. In 1775, he believed that the resulting gas was dephlogisticated air, but not yet oxygen. That is, in 1775, Joseph Priestley identified the gas he obtained by heating red mercury oxide with air in general, but having a lower dose of phlogiston than usual. For the phlogiston chemist, this was, of course, a completely new kind of gas.

The third official claimant to the discoverers of oxygen, the French chemist Antoine Lavoisier, a lawyer by training, was a very rich man. He was a member of the Farming Company, an organization of financiers that farmed state taxes. From these financial transactions, Lavoisier acquired a huge fortune.

Antoine Lavoisier
()

While still studying at the Faculty of Law at the University of Paris, the future general farmer and an outstanding chemist simultaneously studied the natural sciences. Lavoisier invested part of his fortune in the arrangement of a chemical laboratory, equipped with excellent equipment for those times, which became the scientific center of Paris. In his laboratory, Lavoisier conducted numerous experiments in which he determined changes in the masses of substances during their calcination and combustion. Lavoisier proved that carbon dioxide (carbon dioxide) is a combination of oxygen with "coal" (carbon), and water is a combination of oxygen with hydrogen. He experimentally showed that when breathing, oxygen is absorbed and carbon dioxide is formed, that is, the breathing process is similar to the combustion process. Moreover, the French chemist established that the formation of carbon dioxide during respiration is the main source of "animal heat". Lavoisier was one of the first to try to explain the complex physiological processes occurring in a living organism in terms of chemistry.

Lavoisier became one of the founders of classical chemistry. He discovered the law of conservation of matter, introduced the concept of " chemical element" and "chemical compound", proved that breathing is like a combustion process and is a source of heat in the body:

Who knows what other discoveries this outstanding scientist would have made if he had not suffered the fate of the victims of revolutionary terror? Antoine was executed during the French Revolution on February 1, 1794. Lavoisier knew that only one-fifth of the air binds with combustible substances, but the nature of this part was not clear to him. When Priestley informed him in 1774 of the discovery of "dephlogisticated air", he immediately realized that this was the very part of the air that, during combustion, combined with combustible substances. Repeating Priestley's experiments, Lavoisier concluded that atmospheric air consists of a mixture of "vital" (oxygen) and "suffocating" (nitrogen) air and explained the combustion process by combining substances with oxygen.
At the beginning of 1775, Lavoisier reported that the gas obtained after heating the red oxide of mercury is "air as such without changes (except that) ... it turns out to be purer, more breathable." By 1777, probably not without a hint from Priestley, Lavoisier concluded that it was a special variety of gas, one of the main constituents of the atmosphere.
Thus, the more important figure in the history of the discovery of oxygen is Lavoisier, and not Scheele and Priestley. They just released new gas - that's all. writes about it: “Both of them did not know what was in their hands. The element that was destined to revolutionize chemistry disappeared in their hands without a trace... The one who actually discovered oxygen, therefore, remains Lavoisier, and not the two who only described oxygen, not even guessing what they were describing.
Antoine Lavoisier's research played an outstanding role in the development of chemistry in the 18th century. First of all, we are talking about his creation of a scientific theory of combustion, which marked the rejection of the theory of phlogiston, which radically distinguishes his work from the experiments of Scheele and Priestley.
In the fight against supporters of the phlogiston theory, Lavoisier had a wonderful ally who helped him well in his work. Scheele and Priestley also had such an ally, but they did not always use his services and did not attach much importance to his advice. Lavoisier's main assistant was ... scales.
Starting any experiment, Lavoisier almost always carefully weighed all the substances that were supposed to undergo chemical transformation, and at the end of the experiment he weighed again.

Scales Lavoisier.

Like Scheele, Lavoisier also tried to burn phosphorus in a closed flask. But Lavoisier was not at a loss to guess where a fifth of the air disappeared during combustion. Libra gave him a completely accurate answer on this score. Before putting a piece of phosphorus into a flask and setting it on fire, Lavoisier weighed it. And when the phosphorus burned out, Lavoisier weighed out all the dry phosphoric acid that remained in the flask. According to the theory of phosphoric acid phlogiston, there should have been less phosphorus than there was before combustion, since, when burned, phosphorus was destroyed and lost phlogiston. Even if we assume that phlogiston has no weight at all, then phosphoric acid should weigh exactly as much as the phosphorus from which it was obtained weighed. However, it turned out that the white frost, which settled on the walls of the flask after combustion, weighs more than the burnt phosphorus. Consequently, the very part of the air that allegedly disappeared from the flask did not actually leave it at all, but simply joined the phosphorus during combustion. From this compound, phosphoric acid was obtained. Now we call this substance phosphoric anhydride. Lavoisier understood that the combustion of phosphorus was no exception. His experiments showed that whenever any substance burns or metal rusts, the same thing happens.
Interestingly, fifteen years before Lavoisier, our brilliant compatriot Mikhail Vasilyevich Lomonosov compared the weight of a sealed retort with metal before and after calcination. “Experiments were made in tightly fused vessels in order to investigate whether the weight of the metal comes from pure heat,” Lomonosov wrote in 1756, and added the result in two lines: “These experiments found that ... without passing external air, the weight of the burnt metal remains in one measure. So Lomonosov dealt a strong blow to the theory of phlogiston shared by chemists of that time. But this is not enough: Lomonosov made another remarkable conclusion from his experiments that “all the changes that occur in nature are such a state of affairs that, how much of something is taken from one body, so much is added to another, so if some matter is lost somewhere, then multiply elsewhere." With these words, the great scientist expressed one of the most important laws of chemistry - the law of conservation of matter.
Lavoisier began his experiments on the combustion of substances in 1772 and by the end of the year presented to the Academy some results that seemed to him important. In the note he attached, it was reported that during the combustion of sulfur and phosphorus, the weight of the combustion products becomes greater than the weight of the starting materials due to the binding of air, and the weight of lead litharge (lead oxide) decreases when reduced to lead, while a significant amount of air is released.
In 1877, the scientist presented his theory of combustion at a meeting of the Academy of Sciences. The conclusions he made significantly weakened the foundations of the theory of phlogiston, and final defeat it was inflicted by studies of the composition of water.
So who, after all, is the discoverer of oxygen? And when was it opened? Antoine Lavoisier's claims on this score are more convincing and solid, but even they leave ground for very big doubts.
The thing is that a detailed study of the properties of oxygen and its role in the processes of combustion and the formation of oxides led Lavoisier to the wrong conclusion that this gas is an acid-forming principle. In 1779, Lavoisier even introduced the name “oxygenium” for oxygen (from the Greek “oxide” - sour, and “gennao” - I give birth) - “giving birth to acids”.
The discovery of oxygen, apparently, is the fruit of the collective mind and mutually inducing creativity of all the scientists listed in this essay.
What Lavoisier wrote about in his papers beginning in 1777 was not so much the discovery of oxygen as the oxygen theory of combustion. This theory was the key to a restructuring of chemistry so profound that it is usually called a revolution in chemistry. Long before Lavoisier played his part in the discovery of the new gas, he was convinced that there was something wrong with the phlogiston theory and that burning bodies were consuming some part of the atmosphere. He reported many of his thoughts on this subject in notes deposited with the French Academy in 1772. Lavoisier's work on the question of the existence of oxygen further strengthened his earlier opinion that a miscalculation had been made somewhere. She suggested to him what he was already ready to discover - the nature of the substance that, when oxidized, is absorbed from the atmosphere.

Currently, oxygen is very widely used in many areas of human activity. It is used to intensify chemical processes in many industries (for example, in the production of sulfuric and nitric acids, in the blast furnace process). Oxygen is used to obtain high temperatures, for which various combustible gases (hydrogen, acetylene) are burned in special burners. Mixtures of liquid oxygen with coal powder, wood flour or other combustible substances, called oxyliquites, have very strong explosive properties and are used in demolition work.
Oxygen has long been widely used in medicine, and it has become a familiar attribute of critical care medicine. At the same time, not every anesthesiologist-resuscitator knows how to get the gas so necessary for his daily activities.
In the 19th century, the possibilities for obtaining oxygen were limited, and it was obtained only by laboratory methods. In the laboratory, oxygen is obtained from its compounds with other elements. Most often, oxygen is obtained by heating such substances (which contain oxygen in a bound form), such as potassium permanganate (potassium permanganate), potassium chlorate (bertolet salt), potassium nitrate (nitrate):

potassium permanganate

heating

potassium manganate

manganese dioxide

oxygen

potassium chlorate

heating

potassium chloride

oxygen

potassium nitrate

heating

potassium nitrite

oxygen

It is convenient to obtain oxygen in the laboratory and from hydrogen peroxide:

hydrogen peroxide

catalyst

oxygen

Hydrogen peroxide is usually used as a 3% aqueous solution.
The method of obtaining oxygen from metal peroxides is interesting, because carbon dioxide is absorbed simultaneously with the release of oxygen.

sodium peroxide

carbon dioxide

oxygen

On modern nuclear submarines, where there is a powerful and almost inexhaustible source of electrical energy, it is possible to obtain oxygen by the decomposition of water under the action of an electric current (electrolysis of water):

electricity

oxygen

The easiest way to get oxygen is from air, because air is not a compound, and it is not so difficult to separate air. The boiling points of nitrogen and oxygen differ (at atmospheric pressure) by 12.8 ° C. Therefore, liquid air can be separated into components in distillation columns in the same way as, for example, oil is divided. But in order to turn air into a liquid, it must be cooled to -196 ° C and a pressure of about 200 atmospheres must be created.
Liquid oxygen boils at a "higher" temperature (-183°C) than liquid nitrogen (-196°C). Therefore, when "heating" liquid air, when the temperature of this very cold liquid slowly rises from -200 ° C to -180 ° C, first of all, at -196 ° C, nitrogen is distilled (which is again liquefied) and only then oxygen is distilled. If such a distillation of liquid nitrogen and oxygen is carried out repeatedly, then very pure oxygen can be obtained. It is usually stored in compressed form in steel cylinders painted blue. The characteristic blue color of the cylinders is needed so that oxygen cannot be confused with some other compressed gas.

Literature

Axelrod in our life - M .: Knowledge, 1977

Journal - chemistry at school No. 8 2007

100 great scientific discoveries

Dmitry Samin

Fundamentals of the universe

Oxygen

Surprisingly, oxygen has been discovered several times. The first information about him is found already in the VIII century in the treatise of the Chinese alchemist Mao Hoa. The Chinese imagined that this gas (“yin”) was an integral part of the air, and they called it the “active principle”! The inhabitants of the largest Asian country also knew that oxygen combines with charcoal, burning sulfur, some metals. The Chinese could also obtain oxygen using saltpeter-type compounds.

All this ancient information was gradually forgotten. It was only in the 15th century that oxygen was mentioned in passing great Leonardo da Vinci.

It was rediscovered in the 17th century by the Dutchman Drebbel. Very little is known about him. Probably that was great inventor and 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 1620, 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) in the family 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, in addition to theology, Priestley 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, in 1767 Priestley wrote a monograph, The 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: “Having taken out a lens with a diameter of 2 inches, with a focal length of 20 inches, I 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 arouse such surprise in J. Priestley? - asks Yu.I. Solovyov. - A staunch supporter of the doctrine of phlogiston, he considered mercury oxide as a simple substance formed by heating mercury in air and, therefore, devoid of phlogiston. Therefore, the release of "dephlogisticated air" from mercury oxide when heated seemed to him simply impossible. That is why he was "so far from understanding what he really received" ... In 1775, he described the properties that distinguish the "new air" from the "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 unbelievable if they told me about them.

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 arrived in Paris and reported his discovery to Lavoisier. The latter immediately understood 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 at present the most important subject of chemistry. This elastic fluid has many special properties, the study of which contributes to new discoveries. Amazing fire, this product of chemistry, shows us that without air it cannot be produced ... "

Carl Wilhelm Scheele (1742-1786) was born into the family of a brewer and grain merchant in the Swedish city of Stralsund. 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 action 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 the chemist Thorburn Bergman worked at the university. 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 carried out in 1768-1773.

From this treatise it is clear that Scheele 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 which the circulation of blood and juices in animals and plants is maintained ... I am inclined to think that “fire air” consists of an acidic thin matter combined with phlogiston, and probably that all acids got their origin from "fiery air".

Scheele explained his results by the assumption that heat is a combination of "fiery air" (oxygen) and phlogiston. Therefore, he, like M.V. 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 "fiery air" and his theory. “We have already noted,” wrote Bergman, “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 into the air and are easily explained by the fact that it was 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 previously occupied volume.

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 - ed.), spoiled "mephitic air" (nitrogen - ed. note) and essential acid (carbon dioxide - ed. note). The first Priestley called, not only incorrectly, but with a stretch, “dephlogisticated air”, Scheele - “fiery air”, since he alone supports the fire, while the other two extinguish it ... I repeated, with various changes, the main experiments on which he (Scheele) based his conclusions, and found them to be absolutely 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, as can be seen, is a real elemental substance that is part of many matters. That is why I have placed the good air above the phlogiston in my new affinity table... In conclusion, I must say that this wonderful work was completed two years ago, although for various reasons, which it is superfluous to mention here , published just now. 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.

Muraviikha secondary school

"The Amazing Story of the Discovery of Oxygen"

Performed:

Malova Vika Grade 9 Supervisor:

Mikhailenko V.D. Chemistry teacher

Ant, 2009

Atmospheric oxygen consists of diatomic molecules. A gaseous substance, odorless and colorless, therefore not perceptible by any sense organs. However, the disadvantage, and even more so its absence in the atmosphere, we would have discovered very quickly. Oxygen reacts with many substances without heating. When heated in an oxygen atmosphere or in air, many simple and complex substances burn out, and various oxides are formed.

Oxygen is ubiquitous. It is the most abundant element on earth. In significant quantities, it is part of the air, water, soil, animals, plants. Oxygen in the Earth's atmosphere began to accumulate as a result of the activity of primary photosynthetic organisms, which probably appeared about 2.8 billion years ago. It is believed that 2 billion years ago the atmosphere already contained about 1% oxygen; Gradually, it turned from a reducing into an oxidizing one, and about 400 million years ago it acquired its modern composition. The presence of oxygen in the atmosphere largely determined the nature of biological evolution. Oxygen is the main biogenic element that is part of the molecules of all the most important substances that provide the structure and functions of cells - proteins, nucleic acids, carbohydrates, lipids, as well as many low molecular weight compounds. There is much more oxygen in every plant or animal than any other element.

Great discoveries, as a rule, were usually made completely by accident. Zeal, perseverance, purposefulness - all these commendable qualities undoubtedly contribute to obtaining outstanding scientific results, but in no way guarantee them. One must also, as they say, be born under a lucky star.

In the classic discussion about the discovery of oxygen, three scientists are considered at once, who have a legal right to claim this great discovery. It's sh the Swedish chemist Carl Wilhelm Scheele, the English priest Joseph Priestley, and the French chemist Antoine Lavoisier. .
The very first claimant to obtain a relatively pure oxygen sample was the Swedish pharmacist Carl Wilhelm Scheele (1742-1786).

Karl Wilhelm Scheele was born on December 9, 1742 in Stralsund (Pomerania), which then belonged to the Kingdom of Sweden, in the family of a small merchant. As a child, he attended a private boarding school, studied at the gymnasium. Entering an apprenticeship at the Bauch pharmacy in Gothenburg (1756), he mastered the basics of pharmacy and laboratory practice, diligently studied (mainly at night) the works of chemists I. Kunkel, N. Lemery, G. Stahl. The teaching, according to the customs of that time, was to last about ten years. Karl Scheele successfully passed the exams six years later and received the title of pharmacist. Having perfectly mastered the profession and, having moved to Stockholm, Scheele proceeds to independent scientific research. He worked in pharmacies in Stockholm, Uppsala, Köping.
The works and discoveries of Scheele cover all the chemistry of that time: the doctrine of gases, chemical analysis, the chemistry of minerals, the beginnings of organic chemistry (which has not yet emerged as an independent science).
Scheele was the first to obtain and study potassium permanganate KMnO4 - the well-known "potassium permanganate", which is now widely used in chemical experiments and in medicine, developed a method for obtaining phosphorus P from bones, and discovered hydrogen sulfide H3S. The most significant work of Karl Wilhelm Scheele is the Chemical Treatise on Air and Fire, 1777. This book contains the results of his numerous e experiments 1768-1773 for the study of gases and combustion processes. It can be seen from the Treatise that Scheele - independently of Priestley and Lavoisier and two years before them - discovered oxygen and described its properties in detail. At the same time, oxygen was obtained by him in many ways: by calcining mercury oxide (as Priestley and Lavoisier did), by heating mercury carbonate and silver carbonate, etc. Undoubtedly, Scheele was the first (1772) to "handle" pure oxygen.

How it was? While living in Uppsala, Scheele began to study the nature of fire, and he soon had to think about what part the air takes in combustion.
Air was then considered an element - a homogeneous substance that cannot be split into even simpler constituent parts by any force. Scheele, too, was of the same opinion at first. But soon he changed it, as he began to conduct experiments with various chemicals in vessels tightly closed on all sides. Whatever substances Scheele tried to burn in closed vessels, he always found the same curious phenomenon: the air that was in the vessel was necessarily reduced by one-fifth during combustion, and at the end of the experiment, water necessarily filled one-fifth of the volume of the flask, which is clearly seen in the figure below from Scheele's manuscript. And he was struck by the idea that the air is not homogeneous.

.

Then he began to study the decomposition by heating of many substances (among which was KNO3 saltpeter) and received a gas that supported breathing and combustion.
Karl Scheele wanted to solve the mystery of fire and at the same time unexpectedly discovered that air is not an element, but a mixture of two gases, which he called air "fiery" and air "unfit". This was the greatest of all Scheele's discoveries.
Scheele manuscript page
But in reality, the mystery of fire and the "fiery" air he received remained a mystery to him. The phlogiston theory prevailing at that time was to blame for everything, according to which it was believed that any substance can burn only if it contains a lot of special combustible matter - phlogiston, and combustion is the decay of a complex combustible substance into a special fiery element - phlogiston - and other components. Karl Scheele was also a supporter of this theory, so he explained that “fiery air” has a great affinity (attraction) for phlogiston, which is why it burns out in it so quickly, and “unusable” air has no attraction for phlogiston, which is why it goes out every fire. It was pretty plausible, but there was one big mystery that seemed completely inexplicable. Where did the “fiery” air go during combustion from a closed vessel during combustion? Finally, he came up with such an explanation. When a body burns, he said, the phlogiston released from it combines with the "fiery" air, and this invisible compound is so volatile that it imperceptibly seeps through glass, like water through a sieve.
Scheele was indeed the first researcher to obtain a relatively pure oxygen sample (1772). However, he published his results in 1777, later than Joseph Priestley did, so he cannot formally be considered the discoverer of oxygen. But in many academic publications and reference books on chemistry, Karl Wilhelm Scheele is given priority. In addition, he has the indisputable priority of discovering the chemical elements chlorine Cl, fluorine F, barium Ba, molybdenum Mo, tungsten W...
Despite the fact that Scheele did not have higher education and was an ordinary pharmacist, at the age of 32 he was elected a member of the Stockholm Academy of Sciences. He was offered a chair at Uppsala University, a job at the center of the Swedish mining and metallurgical industry in Falun, a chair at the University of Berlin, but the scientist rejected all offers, preferring to do his own experiments.
The second officially recognized contender for the laurels of the discoverer of oxygen is the English priest and chemist Joseph Priestley (1733-1804).

Priestley Joseph - famous English chemist, philosopher and theologian; manufacturer's son. His amazing ability for languages ​​allowed him to easily learn the languages ​​\u200b\u200bof Arabic, Chaldean, Syriac; without the help of a teacher Priestley learned to speak French, German and Italian. Priestley was mainly engaged in physics and chemistry. While still at school, he independently studied philosophy, logic, and mathematics. The doors of the Royal Academy of Sciences opened for Priestley. After spending some time as a professor of languages ​​at the Washington Academy, Priestley settled in Leeds, where he made his famous studies of carbon dioxide, nitrogen dioxide and oxygen. For these studies, Priestley received the Copley Medal from the Royal Society. The Paris Academy elects Priestley as its member. In 1774, Priestley, heating red mercury oxide, releases oxygen, marveling that a candle burns brightly in this gas. the study of further properties of "dephlogisticated" gas owes much to Priestley. Even from these few examples, Priestley's outstanding powers of observation and experimentation are undeniable. If his discoveries did not have the same success and significance for chemistry as the discoveries of his French contemporary, then this is explained by the fact that Priestley, by the very nature of his scientific thought, belonged to the admirers of the theory of phlogiston, which was already surviving at that time.
On August 1, 1774, Joseph Priestley observed the release of "new air" when heated with a biconvex lens without air access to mercury scale, located under a glass dome. This solid substance was known to the alchemists under the name "mercurius calcinatus perce", or burnt mercury. In modern chemical language, this substance is called mercury oxide, and the equation for its decomposition when heated is as follows:

Out of curiosity, Priestley introduced a smoldering candle into the collected gas, and it flared up unusually brightly.
One can now imagine how difficult it was to study chemistry at a time when chemical formulas had not yet been invented. What is written in a short chemical equation, Priestley described in 1774 as follows: “I placed under an inverted jar immersed in mercury, a little powder of Mercurius calcinatus perce. Then I took a small burning glass and directed the rays of the Sun directly into the jar onto the powder. Air began to be released from the powder, which forced the mercury out of the jar. I began to study this air. And I was surprised, even excited to the depths of my soul, that in this air a candle burns better and brighter than in an ordinary atmosphere.
Of course, such a description of the reaction looks very poetic compared to the usual chemical equation, but, unfortunately, it does not reflect the essence of the chemical reaction that has taken place.
Priestley himself, being, like Scheele, a supporter of the theory of phlogiston, also could not explain the essence of the combustion process; he defended his ideas even after Antoine Lavoisier promulgated a new theory of combustion.
The claims of Joseph Priestley's supporters regarding the discovery of oxygen by this particular scientist were based on his priority in obtaining gas, which was later recognized as a special, hitherto unknown type of gas. But Priestley's gas sample was not clean. Besides, if Priestley was the discoverer, then when was the discovery made? In 1774, he believed that he had obtained nitrous oxide, that is, a kind of gas that he already knew. In 1775, he believed that the resulting gas was dephlogisticated air, but not yet oxygen. That is, in 1775, Joseph Priestley identified the gas he obtained by heating red mercury oxide with air in general, but having a lower dose of phlogiston than usual. For the phlogiston chemist, this was, of course, a completely new kind of gas.

The third official claimant to the discoverers of oxygen, the French chemist Antoine Lavoisier, a lawyer by training, was a very rich man. He was a member of the Farming Company, an organization of financiers that farmed state taxes. From these financial transactions, Lavoisier acquired a huge fortune.

Antoine Lavoisier
(1743-1794)

While still studying at the Faculty of Law at the University of Paris, the future general farmer and an outstanding chemist simultaneously studied the natural sciences. Part of his fortune Lavoisier invested in the arrangement of a chemical laboratory, equipped with excellent equipment for those times, which became the scientific center of Paris. In his laboratory, Lavoisier conducted numerous experiments in which he determined changes in the masses of substances during their calcination and combustion. Lavoisier proved that carbon dioxide (carbon dioxide) is a combination of oxygen with "coal" (carbon), and water is a combination of oxygen with hydrogen. He experimentally showed that when breathing, oxygen is absorbed and carbon dioxide is formed, that is, the breathing process is similar to the combustion process. Moreover, the French chemist established that the formation of carbon dioxide during respiration is the main source of "animal heat". Lavoisier was one of the first to try to explain the complex physiological processes occurring in a living organism in terms of chemistry.

Lavoisier became one of the founders of classical chemistry. He discovered the law of conservation of substances, introduced the concepts of "chemical element" and "chemical compound", proved that breathing is similar to the combustion process and is a source of heat in the body:

Who knows what other discoveries this outstanding scientist would have made if he had not suffered the fate of the victims of revolutionary terror? Antoine was executed during the French Revolution on February 1, 1794. Lavoisier knew that only one-fifth of the air binds with combustible substances, but the nature of this part was not clear to him. When Priestley informed him in 1774 of the discovery of "dephlogisticated air", he immediately realized that this was the very part of the air that, during combustion, combined with combustible substances. Repeating Priestley's experiments, Lavoisier concluded that atmospheric air consists of a mixture of "vital" (oxygen) and "suffocating" (nitrogen) air and explained the combustion process by combining substances with oxygen.
At the beginning of 1775, Lavoisier reported that the gas obtained after heating the red oxide of mercury is "air as such without changes (except that) ... it turns out to be purer, more breathable." By 1777, probably not without a hint from Priestley, Lavoisier concluded that it was a special variety of gas, one of the main constituents of the atmosphere.
Thus, the more important figure in the history of the discovery of oxygen is Lavoisier, and not Scheele and Priestley. They just released new gas - that's all. Friedrich Engels would later write about this: “Both of them never found out what was in their hands. The element that was destined to revolutionize chemistry disappeared in their hands without a trace... The one who actually discovered oxygen, therefore, remains Lavoisier, and not the two who only described oxygen, not even guessing what they were describing.
Antoine Lavoisier's research played an outstanding role in the development of chemistry in the 18th century. First of all, we are talking about his creation of a scientific theory of combustion, which marked the rejection of the theory of phlogiston, which radically distinguishes his work from the experiments of Scheele and Priestley.
In the fight against supporters of the phlogiston theory, Lavoisier had a wonderful ally who helped him well in his work. Scheele and Priestley also had such an ally, but they did not always use his services and did not attach much importance to his advice. Lavoisier's main assistant was ... scales.
Starting any experiment, Lavoisier almost always carefully weighed all the substances that were supposed to undergo chemical transformation, and at the end of the experiment he weighed again.

Scales Lavoisier.

Like Scheele, Lavoisier also tried to burn phosphorus in a closed flask. But Lavoisier was not at a loss to guess where a fifth of the air disappeared during combustion. Libra gave him a completely accurate answer on this score. Before putting a piece of phosphorus into a flask and setting it on fire, Lavoisier weighed it. And when the phosphorus burned out, Lavoisier weighed out all the dry phosphoric acid that remained in the flask. According to the theory of phosphoric acid phlogiston, there should have been less phosphorus than there was before combustion, since, when burned, phosphorus was destroyed and lost phlogiston. Even if we assume that phlogiston has no weight at all, then phosphoric acid should weigh exactly as much as the phosphorus from which it was obtained weighed. However, it turned out that the white frost, which settled on the walls of the flask after combustion, weighs more than the burnt phosphorus. Consequently, the very part of the air that supposedly disappeared from the flask did not actually leave it at all, but simply joined the phosphorus during combustion. From this compound, phosphoric acid was obtained. Now we call this substance phosphoric anhydride. Lavoisier understood that the combustion of phosphorus was no exception. His experiments showed that whenever any substance burns or metal rusts, the same thing happens.
It is interesting that our brilliant compatriot Mikhail Vasilyevich Lomonosov fifteen years before Lavoisier compared the weight of a sealed retort with metal before and after calcination. “Experiments were made in tightly fused vessels in order to investigate whether the weight of the metal comes from pure heat,” Lomonosov wrote in 1756, and added the result in two lines: “These experiments found that ... without passing external air, the weight of the burnt metal remains in one measure. So Lomonosov dealt a strong blow to the theory of phlogiston shared by chemists of that time. But this is not enough: Lomonosov made another remarkable conclusion from his experiments that “all the changes that occur in nature are such a state of affairs that, how much of something is taken from one body, so much is added to another, so if some matter is lost somewhere, then multiply elsewhere." With these words, the great scientist expressed one of the most important laws of chemistry - the law of conservation of matter.
Lavoisier began his experiments on the combustion of substances in 1772, and by the end of the year presented to the Academy some of the results that seemed to him important. In the note he attached, it was reported that during the combustion of sulfur and phosphorus, the weight of the combustion products becomes greater than the weight of the starting materials due to the binding of air, and the weight of lead litharge (lead oxide) decreases when reduced to lead, while a significant amount of air is released.
In 1877, the scientist presented his theory of combustion at a meeting of the Academy of Sciences. The conclusions he made significantly weakened the foundations of the theory of phlogiston, and the final defeat was inflicted on it by studies of the composition of water.
So who, after all, is the discoverer of oxygen? And when was it opened? Antoine Lavoisier's claims on this score are more convincing and solid, but even they leave ground for very big doubts.
The thing is that a detailed study of the properties of oxygen and its role in the processes of combustion and the formation of oxides led Lavoisier to the wrong conclusion that this gas is an acid-forming principle. In 1779, Lavoisier even introduced the name “oxygenium” for oxygen (from the Greek “oxide” - sour, and “gennao” - I give birth) - “giving birth to acids”.
The opening of oxygen appears to be the fruit of collective mind and mutually inducing creativity of all the scientists listed in this essay.
What Lavoisier wrote about in his papers beginning in 1777 was not so much the discovery of oxygen as the oxygen theory of combustion. This theory was the key to a restructuring of chemistry so profound that it is usually called a revolution in chemistry. Long before Lavoisier played his part in the discovery of the new gas, he was convinced that there was something wrong with the phlogiston theory and that burning bodies were consuming some part of the atmosphere. He reported many of his thoughts on this subject in notes deposited with the French Academy in 1772. Lavoisier's work on the question of the existence of oxygen further strengthened his earlier opinion that a miscalculation had been made somewhere. She suggested to him what he was already ready to discover - the nature of the substance that, when oxidized, is absorbed from the atmosphere.

Currently, oxygen is very widely used in many areas of human activity. It is used to intensify chemical processes in many industries (for example, in the production of sulfuric and nitric acids, in the blast furnace process). Oxygen is used to obtain high temperatures, for which various combustible gases (hydrogen, acetylene) are burned in special burners. Mixtures of liquid oxygen with coal powder, wood flour or other combustible substances, called oxyliquites, have very strong explosive properties and are used in demolition work.
Oxygen has long been widely used in medicine, and it has become a familiar attribute of critical care medicine. At the same time, not every anesthesiologist-resuscitator knows how to get the gas so necessary for his daily activities.
In the 19th century, the possibilities for obtaining oxygen were limited, and it was obtained only by laboratory methods. In the laboratory, oxygen is obtained from its compounds with other elements. Most often, oxygen is obtained by heating such substances (which contain oxygen in a bound form), such as potassium permanganate (potassium permanganate), potassium chlorate (bertolet salt), potassium nitrate (nitrate):

It is convenient to obtain oxygen in the laboratory and from hydrogen peroxide:

Hydrogen peroxide is usually used as a 3% aqueous solution.
The method of obtaining oxygen from metal peroxides is interesting, because carbon dioxide is absorbed simultaneously with the release of oxygen.

On modern nuclear submarines, where there is a powerful and almost inexhaustible source of electrical energy, it is possible to obtain oxygen by the decomposition of water under the action of an electric current (electrolysis of water):

The easiest way to get oxygen is from air, because air is not a compound, and it is not so difficult to separate air. The boiling points of nitrogen and oxygen differ (at atmospheric pressure) by 12.8 ° C. Therefore, liquid air can be separated into components in distillation columns in the same way as, for example, oil is divided. But in order to turn air into a liquid, it must be cooled to -196 ° C and a pressure of about 200 atmospheres must be created.
Liquid oxygen boils at a "higher" temperature (-183°C) than liquid nitrogen (-196°C). Therefore, when "heating" liquid air, when the temperature of this very cold liquid slowly rises from -200 ° C to -180 ° C, first of all, at -196 ° C, nitrogen is distilled (which is again liquefied) and only then oxygen is distilled. If such a distillation of liquid nitrogen and oxygen is carried out repeatedly, then very pure oxygen can be obtained. It is usually stored in compressed form in steel cylinders painted blue. The characteristic blue color of the cylinders is needed so that oxygen cannot be confused with some other compressed gas.
. 1781 - history - Christian, Jewish and ... in this case there is nothing amazing that he was part of ... blood in a minimal amount oxygen? One of the features... impeccable logic and rejoiced in it discoveries. I could easily...

Oxygen is an odorless and tasteless gas, found in three forms: atomic, ordinary and ozone - the most common on Earth and the third most common in the Universe (after hydrogen and helium) element of the periodic table, its share (as part of various compounds (in total more than 1500 compounds, mainly silicates) account for about 47.4% of the mass of the solid earth's crust. Sea and fresh waters contain a huge amount of bound oxygen - 88.8% (by mass), in the atmosphere the content of free oxygen is 20.95% by volume and 23.12% by mass. Once in the lungs, it reaches all the cells of the body with the help of red blood cells. In the body, it burns food, producing the heat necessary for human activity. Oxygen is a constituent of many organic substances and is present in all living cells. All major classes of structural molecules in living organisms, such as proteins, carbohydrates, and fats, contain oxygen, as do the major inorganic compounds that make up cell membranes, teeth, and bones. In terms of the number of atoms in living cells, it is about 25%, in terms of mass fraction - about 65%. The oxygen cycle in nature is provided by green plants that absorb carbon dioxide from the air and release free oxygen from it with the participation of chlorophyll. Therefore, its content in the atmosphere is almost unchanged.

Oxygen combines very well with other elements. This reaction is called "oxidation". We see slow oxidation everywhere. Metal rusts, paint dries, alcohol turns into vinegar - all this is oxidation. Almost any oxidation releases heat. With rapid oxidation, combustion occurs, since heat is released very quickly, the temperature rises sharply, and a flame appears ...

Since ancient times, it has been known that air is needed for combustion, but for a very long time the combustion process remained incomprehensible. Only in the XVII century. Mayow and Boyle, independently of each other, expressed the idea that the air contains a certain substance that supports combustion, but this completely rational hypothesis was not developed at that time, since the idea of ​​combustion as a process of connecting a burning body with a certain constituent part of the air seemed to at that time contradicting the so obvious act of decomposition of a burning body into elementary constituent parts. It is on this basis at the turn of the XVII century. the theory of phlogiston, created by Becher and Stahl, arose. With the onset of the chemical-analytical period in the development of chemistry (the second half of the 18th century) and the emergence of "pneumatic chemistry" - one of the main branches of the chemical-analytical direction - combustion, as well as respiration, again attracted the attention of researchers.

Oxygen has an interesting history of discovery. It can be said that it was opened three times. The properties of oxygen, such as gaseousness, colorlessness, lack of taste and smell, contributed to the delay in its discovery.

An interesting fact is that for the first time oxygen was isolated not by chemists. This was done by the inventor of the submarine K. Drebbel at the beginning of the 17th century. He used this gas for breathing in a boat, when immersed in water. But the work of the inventor was classified. Therefore, the work of K. Drebbel did not play a big role in the development of chemistry.

It is officially believed that oxygen was discovered August 1, 1774, when the English chemist Joseph Priestley observed the release of "new air" when heated with a powerful biconvex lens without air access to mercury scale under a glass cap. This solid substance was known to the alchemists under the name "Mercurius calcinatus perse", or burnt mercury, in modern chemical language this substance is called mercury oxide. The gas, unknown to him, obtained by heating mercury oxide, he led out through a tube into a vessel filled not with water, but with mercury, since Priestley had already been convinced that water dissolves gases too well. Out of curiosity, Priestley introduced a smoldering candle into the collected gas, and it flared up unusually brightly. The equation for the decomposition of mercury oxide when heated is as follows:

You can now imagine how difficult it was to study chemistry at a time when chemical formulas had not yet been invented. The above short chemical equation, Priestley described in 1774 as follows: “I placed under an inverted jar immersed in mercury, a little powder of Mercurius calcinatus perce. Then I took a small burning glass and directed the rays of the Sun directly into the jar onto the powder. Air began to be released from the powder, which forced the mercury out of the jar. I began to study this air. And I was surprised, even excited to the depths of my soul, that in this air a candle burns better and brighter than in an ordinary atmosphere. Of course, such a description of the reaction looks very poetic compared to the usual chemical equation, but, unfortunately, it does not reflect the essence of the chemical reaction that has taken place.

However, Priestley was not the first scientist to receive oxygen. A few years earlier (in 1771), Swedish chemist Carl Wilhelm Scheele obtained oxygen. Living in Uppsala, Sheele, an apprentice pharmacist, began to study the nature of fire, and he soon had to think about what part the air takes in combustion. He already knew that a hundred years ago, Robert Boyle and other scientists proved that a candle, coal and any other combustible body can burn only where there is enough air. No one in those days could, however, plainly explain why everything was happening and why, in fact, the burning body needed air. Air was then considered an element - a homogeneous substance that cannot be split into even simpler constituent parts by any force. Scheele, too, was of the same opinion at first. But soon he had to change it after he began to conduct experiments with various chemicals in vessels tightly closed on all sides. Whatever substances Scheele tried to burn in closed vessels, he always found the same curious phenomenon: the air that was in the vessel was necessarily reduced by one-fifth during combustion, and at the end of the experiment, water necessarily filled one-fifth of the volume of the flask, which is clearly seen in the figure below from Scheele's manuscript. And he was struck by the idea that the air is not homogeneous. Then he began to study the decomposition by heating of many substances (mercury oxide (as Priestley and Lavoisier did), mercury carbonate and silver carbonate, as well as KNO3 nitrate) and received a gas that supported breathing and combustion. According to some reports, already in 1771, Karl Scheele, when heating pyrolusite with concentrated sulfuric acid, observed the release of "virtol air" that supports combustion, i.e. oxygen. Karl Scheele wanted to solve the mystery of fire and at the same time unexpectedly discovered that air is not an element, but a mixture of two gases, which he called air "fiery" and air "unfit". This was the greatest of all Scheele's discoveries. Scheele described his discovery in the treatise “On Air and Fire” published in 1777 (precisely because the book was published later than Priestley announced his discovery, the latter is considered the discoverer of oxygen) ...

But neither Priestley nor Scheele understood what they had discovered. They discovered a new gas. Only and everything. And until the end of their lives they remained devoted to the theory of phlogiston, which at the end of the 18th century became a brake on the development of science. Karl Scheele, for example, explained that “fiery air” has a great affinity (attraction) for phlogiston, which is why it burns out in it so quickly, and “unusable” air has no attraction for phlogiston, which is why any fire goes out in it. It was pretty plausible, but there was one big mystery that seemed completely inexplicable. Where did the “fiery” air go during combustion from a closed vessel during combustion? Finally, he came up with such an explanation. When a body burns, he said, the phlogiston released from it combines with the "fiery" air, and this invisible compound is so volatile that it imperceptibly seeps through glass, like water through a sieve.

The claims of Joseph Priestley's supporters regarding the discovery of oxygen by this particular scientist were based on his priority in obtaining gas, which was later recognized as a special, hitherto unknown type of gas. But the sample of gas obtained by Priestley was not pure, and if the production of oxygen with impurities is considered his discovery, then the same can be said in principle about all those who have ever enclosed atmospheric air in a vessel. Besides, if Priestley was the discoverer, then when was the discovery made? In 1774, he believed that he had obtained nitrous oxide, that is, a kind of gas that he already knew. In 1775, he believed that the resulting gas was dephlogisticated air, but not yet oxygen. That is, in 1775, Joseph Priestley identified the gas he obtained by heating red mercury oxide with air in general, but having a lower dose of phlogiston than usual. For the phlogiston chemist, this was, of course, a completely new kind of gas.

Friedrich Engels would later write about this: Neither of them knew what was in their hands. The element that was destined to revolutionize chemistry disappeared without a trace in their hands ... The one who actually discovered oxygen, therefore, remains Lavoisier, and not the two who only described oxygen, not even guessing what they were describing". Another great chemist of the 18th century, the Frenchman Antoine Lavoisier, did away with phlogiston. And when this was done, the strange disappearance of the "fiery air" and many other incomprehensible phenomena immediately lost all their mystery.

Antoine Lavoisier (Lavoisier, Antoine Laurent, 1743-1794), began the work that led him to the discovery after an experiment by Joseph Priestley in 1774, and perhaps due to a hint from Priestley. From his own experiments and previous experiments by Priestley and Scheele, Lavoisier already knew that only one-fifth of the air binds with combustible substances, but the nature of this part was not clear to him. When Priestley informed him in 1774 of the discovery of "dephlogisticated air", he immediately realized that this was the very part of the air that, during combustion, combined with combustible substances. Repeating Priestley's experiments, Lavoisier concluded that atmospheric air consists of a mixture of "vital" (oxygen) and "suffocating" (nitrogen) air and explained the combustion process by combining substances with oxygen.

At the beginning of 1775, Lavoisier reported that the gas obtained after heating the red oxide of mercury is "air as such without changes (except that) ... it turns out to be purer, more breathable." By 1777, probably not without a second hint from Priestley, Lavoisier concluded that it was a special variety of gas, one of the main constituents of the atmosphere. True, Priestley himself, as a supporter of the phlogiston theory, could never agree with such a conclusion.

Scales Lavoisier.

In the fight against supporters of the phlogiston theory, Lavoisier had a wonderful ally who helped him well in his work. Scheele and Priestley also had such an ally, but they did not always use his services and did not attach much importance to his advice. Lavoisier's main assistant was ... scales. Starting any experiment, Lavoisier almost always carefully weighed all the substances that were supposed to undergo chemical transformation, and at the end of the experiment he weighed again.

Like Scheele, Lavoisier also tried to burn phosphorus in a closed flask. But Lavoisier was not at a loss to guess where a fifth of the air disappeared during combustion. Libra gave him a completely accurate answer on this score. Before putting a piece of phosphorus into a flask and setting it on fire, Lavoisier weighed it. And when the phosphorus burned out, Lavoisier weighed out all the dry phosphoric acid that remained in the flask. According to the theory of phosphoric acid phlogiston, there should have been less phosphorus than there was before combustion, since, when burned, phosphorus was destroyed and lost phlogiston. Even if we assume that phlogiston has no weight at all, then phosphoric acid should weigh exactly as much as the phosphorus from which it was obtained weighed. However, it turned out that the white frost, which settled on the walls of the flask after combustion, weighs more than the burnt phosphorus. Consequently, the very part of the air that supposedly disappeared from the flask did not actually leave it at all, but simply joined the phosphorus during combustion. From this compound, phosphoric acid was obtained. Now we call this substance phosphoric anhydride. Lavoisier understood that the combustion of phosphorus was no exception. His experiments showed that whenever any substance burns or metal rusts, the same thing happens.

Lavoisier began his experiments on the combustion of substances in 1772, and by the end of the year presented to the Academy some of the results that seemed to him important. In the note he attached, it was reported that during the combustion of sulfur and phosphorus, the weight of the combustion products becomes greater than the weight of the starting materials due to the binding of air, and the weight of lead litharge (lead oxide) decreases when reduced to lead, while a significant amount of air is released. In 1877, the scientist presented his theory of combustion at a meeting of the Academy of Sciences. The conclusions he made significantly weakened the foundations of the theory of phlogiston, and the final defeat was inflicted on it by studies of the composition of water. In 1783, Lavoisier, repeating Cavendish's experiments on burning "combustible" air (hydrogen), concluded that "water is not at all a simple body", but is a combination of hydrogen and oxygen. It can be decomposed by passing water vapor through a red-hot gun barrel. He proved the latter together with the lieutenant of the engineering troops J. Meunier.

It is interesting that the brilliant scientist Mikhail Vasilievich Lomonosov fifteen years before Lavoisier compared the weight of a sealed retort with metal before and after calcination. “Experiments were made in tightly fused vessels in order to investigate whether the weight of the metal comes from pure heat,” Lomonosov wrote in 1756, and added the result in two lines: “These experiments found that ... without passing external air, the weight of the burnt metal remains in one measure. So Lomonosov dealt a strong blow to the theory of phlogiston shared by chemists of that time. But this is not enough: Lomonosov made another remarkable conclusion from his experiments, that “ all the changes that occur in nature are such a state that, as much of what is taken from one body, so much is added to another, so if some matter decreases somewhere, it multiplies in another place". With these words, the great scientist expressed one of the most important laws of chemistry - the law of conservation of matter. By the way, the word oxygen"(it was also called at the beginning of the 19th century" with acid”), to some extent, it also owes its appearance in the Russian language to M.V. Lomonosov, who introduced, along with other neologisms, the word “acid”; thus the word "oxygen", in turn, was a tracing-paper of the term "oxygen" (fr. oxygène), proposed by A. Lavoisier (from other Greek ὀξύς - "sour" and γεννάω - "I give birth"), which translates as “generating acid”, which is associated with its original meaning - “acid”, which previously meant substances called oxides according to modern international nomenclature.

So who, after all, is the discoverer of oxygen? And when was it opened? Antoine Lavoisier's claims on this score are more convincing and solid, but even they leave ground for very big doubts.

The thing is that a detailed study of the properties of oxygen and its role in the processes of combustion and the formation of oxides led Lavoisier to the wrong conclusion that this gas is an acid-forming principle. In 1779, Lavoisier even introduced the name “oxygenium” for oxygen (from the Greek “oxide” - sour, and “gennao” - I give birth) - “giving birth to acids”. And in 1777, and until the end of his life, Lavoisier insisted that oxygen is an atomic "element of acidity" and that oxygen as a gas is formed only when this "element" combines with "caloric", with the "heat matter" . Can we say on this basis that oxygen had not yet been discovered in 1777? Such temptation can and does arise. The element of acidity was expelled from chemistry only after 1810, and the concept of caloric was dying out before the 1960s. Oxygen came to be regarded as ordinary chemical even before these events, but the discovery of oxygen, apparently, is the fruit of the collective mind and mutually inducing creativity of all the scientists listed in this essay. What Lavoisier wrote about in his papers beginning in 1777 was not so much the discovery of oxygen as the oxygen theory of combustion. This theory was the key to a restructuring of chemistry so profound that it is usually called a revolution in chemistry. Long before Lavoisier played his part in the discovery of the new gas, he was convinced that there was something wrong with the phlogiston theory and that burning bodies were consuming some part of the atmosphere. He reported many of his thoughts on this subject in notes deposited with the French Academy in 1772. Lavoisier's work on the question of the existence of oxygen further strengthened his earlier opinion that a miscalculation had been made somewhere. She suggested to him what he was already ready to discover - the nature of the substance that, when oxidized, is absorbed from the atmosphere.

Whatever it was, and whoever discovered this gas, oxygen is now very widely used in many areas of human activity. It is used to intensify chemical processes in many industries (for example, in the production of sulfuric and nitric acids, in the blast furnace process). Oxygen is used to obtain high temperatures, for which various combustible gases (hydrogen, acetylene) are burned in special burners. Mixtures of liquid oxygen with coal powder, wood flour or other combustible substances, called oxyliquites, have very strong explosive properties and are used in demolition work. Liquid oxygen is used in rocket fuel. In medicine, oxygen is used to support the life of patients with difficulty breathing and to treat certain diseases. However, pure oxygen at normal pressure cannot be breathed for a long time - it is dangerous to health.

But I want to dwell in more detail on one of the very useful and tasty uses of oxygen - oxygen cocktails.

"An oxygen cocktail is an oxygen-saturated drink that forms a foamy" cap ". To form the structure of the cocktail, food foaming agents are used - mainly special compositions for oxygen cocktails, sometimes spum mixtures, even more rarely licorice root extract or dry egg white. Sanatoriums, rest houses and other wellness establishments often add vitaminizing ingredients to the composition of the cocktail.The taste of the oxygen cocktail depends entirely on the components of its base, while oxygen itself has no taste and smell.It is believed that it has tonic properties.It is used for therapeutic and prophylactic purposes as one of the concomitant means oxygen therapy.It can help eliminate chronic fatigue syndrome and get rid of hypoxia, activate cell metabolism, etc." (Wikipedia)

The composition of the oxygen cocktail includes 3 main components: oxygen, a flavoring liquid base and a food foaming agent.

Sources of oxygen can be: cylinders filled with medical oxygen, portable cylinders with an oxygen-air mixture, oxygen concentrators that produce an air mixture with an oxygen concentration of up to 95%, even oxygen pillows.

IN as a liquid cocktail base use juices (apple, pear, grape, cherry, sea buckthorn, raspberry), syrups, water, milk and fruit drinks. It is not recommended to use oily and carbonated liquids, as well as juices with pulp, as they prevent the formation of a homogeneous foam. For therapeutic and prophylactic purposes, healing infusions of plants and herbs, such as hawthorn, immortelle, motherwort and wild rose, are suitable as a basis.

The third component of the oxygen cocktail is the foaming component, due to which the formation of foam in the drink occurs. If earlier it was necessary to use “improvised” foaming agents (raw egg white, which can cause salmonellosis, and alcohol-containing licorice root syrup), now there is a large selection of safe compositions for oxygen cocktails.

There are 3 main ways to make an oxygen cocktail:

Method 1. Using an oxygen cocktail
Pour the liquid base into the container of the cocktail and pour the composition. Stir the liquid until the powder is completely dissolved. Supply oxygen to the cocktail. Take the resulting oxygen foam in portioned glasses. This method is most often used in sanatoriums, kindergartens, schools, where in a short period of time it is necessary to make many portions of an oxygen cocktail of the same taste.

Method 2. Using an oxygen mixer
Pour the liquid base into a container (glass goblet, disposable glass) and pour the composition. Apply oxygen, turn on the whisk of the mixer and beat the contents of the glass until a thick homogeneous foam is obtained. This method ideal for those who do business selling oxygen cocktails. The mixer allows not only to obtain a thick and dense foam, but also to approach each portion individually, using different flavor bases.

Method 3. Using a tube with an aerator
Pour the liquid base into a container (glass goblet, disposable glass), pour the composition and mix thoroughly. Connect the tube with the aerator to the oxygen source (oxygen concentrator, oxygen cartridge) and supply oxygen until the container is filled with foam. The aerator must be completely immersed in the liquid. This method is considered optimal for homemade oxygen cocktails.

Another 1 way from akak.ru. Without oxygen tanks

Buy juice. It must be red! Those. all sorts of apple, peach and orange ones, of course, are also suitable, but red ones foam better. And without any sediment - pulp. Cherry or grape juice is best. Instead of juice, you can take a decoction of herbs or something. Then it will turn out to be even more useful. in general - anything!
Take a vase or glass. Pour juice like whiskey - two fingers (height =)).
MOST IMPORTANT: Drop some licorice root syrup. ATTENTION! you need to calculate from this proportion: 2 tablespoons per liter of juice. You have a little, so the maximum is a teaspoon, and then, it will already be a lot. Mix everything well. Try, experiment. Especially with licorice. you need to find the edge at which it does not taste (I do not like it) and holds bubbles well.
Now the simplest thing: Lower the hose (tube) with the sprayer into the mixture and start blowing. You can inflate with your mouth, or you can use a balloon pump (in the first case, you get a carbon-oxygen cocktail, and in the second, an atmospheric one). You can also buy an oxygen bottle from a pharmacy. But it is quite expensive and the taste does not change at all (as they say - if there is no difference ...). Keep in mind that the slower you blow, the better the foam will be.
And keep in mind that an oxygen cocktail cannot be prepared for the future - it must be drunk immediately after preparation - over time, the foam falls off.

In the course of clinical studies conducted by Russian scientists, it was revealed [source not specified 60 days] that an oxygen cocktail can have the following effects on the body:

Reduce harmful effects environment on the human body
Reduce fatigue, help eliminate chronic fatigue syndrome and hypoxia
improve sleep
Activate cellular metabolism
Improve the condition of the cardiovascular, digestive, respiratory and nervous systems organism
Stimulate cardiac and cerebral circulation
Optimize blood sugar levels, increase hemoglobin
Stimulate the immune system
Contribute to the normal development of the fetus during pregnancy.

Russian medical institutions can be recommended to women during pregnancy, athletes, children and adolescents, residents of large cities with poor environmental conditions, people suffering from hypoxia, diseases of the cardiovascular and digestive systems, immune problems, insomnia, chronic fatigue and excess weight take oxygen cocktails in combination with other means of treatment and prevention.

After taking a cocktail, bouts of flatulence may begin. If you have a serious illness, you should consult your doctor before using the drink. Contraindications to the use of oxygen cocktails can be:

Acute attacks of bronchial asthma
Cholelithiasis
asthmatic status
hyperthermia
Respiratory failure
Body intoxication
Urolithiasis disease
peptic ulcer
Allergic reaction to certain components of the cocktail.

Who discovered oxygen, this most important element for the life of all life on the planet, you will learn from this article.

Who discovered oxygen?

Oxygen has interesting story discoveries. It has been opened three times. This is due to the fact that the properties of the element (colorlessness, gaseousness, lack of smell and taste) slowed down a little this process. But researchers still guessed about its existence.

At the word oxygen, the question immediately arises in our thoughts - who is the chemist who discovered oxygen and carbon dioxide? But the interesting thing is that the element was not first identified by chemists at all. The scientist who discovered oxygen and carbon is an inventor of the 17th century K. Drebbel who designed the submarine. When diving to great depths in water, he used gas for breathing. But his work was strictly classified, so they did not play any role in the development of chemical science.

A century later, oxygen is discovered was two chemists, independently of each other, - Joseph Priestley (English) and Carl Wilhelm Scheele(Swede). Karl Scheele singled out oxygen a little earlier from Priestley, but the Swede's treatise on the discovery came out later than the message about Joseph's grandiose discovery.

Officially, oxygen as a chemical element was discovered by the great French chemist Antoine Laurent Lavoisier. Lavoisier learned about the existence of oxygen from Priestley, 2 months after the discovery of the Englishman. Conducting chemical research in combustion processes, he did not know that not all air contributes to this, but part of it - oxygen. For two years he studied chemical processes, recording all measurements and deviations.

Once a scientist was experimenting with mercury oxide. For the purposes of the experiment, he used a sealed retort. Putting mercury in it, he soldered the retort and heated it. Observing how red mercury oxide is formed, Lavoisier noticed how the volume of air decreases and the quantitative mass of mercury increases. As a result of the experiment, the scientist received 2.5 g of mercury and a gas called oxygen. Lavoisier called it "vital gas".

This is the story of the discovery of the most important element in chemistry for living organisms, which occupies most of the mass of the earth's crust.

We hope that from this article you have learned how the chemical element oxygen was discovered.

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