Which scientist is considered the founder of classical chemistry. History of chemistry

The importance of chemistry in the history of mankind is extremely great. Today, this scientific discipline has many objects and methods of research, thanks to which the reality surrounding us is possible. Achievements in the field of chemistry make it possible to obtain high-strength materials and develop the latest drugs that can save thousands of lives, conduct research activities in related sciences.

Now more than one and a half tens of millions of compounds are known, each of which is capable of entering into a numerous number of reaction interactions. However, mankind has not always possessed such a variety of chemicals and information about them. Chemistry at the current stage of its development is a consequence of previously acquired and carefully structured knowledge.

Throughout the history of chemistry, it has been treated in a very specific way. Some considered this science to be a help to humanity to reach a new stage of its development, others - only magical powers. For it in the Middle Ages burned at the stake. The history of the emergence of chemistry will be considered in more detail. Let us highlight the key historical moments that contribute to the further development of this science.

The formation of chemistry in the ancient policy

There are many theories that say that the history of the development of chemistry began at the turn of our era. This happened with the development of skills and the ability to obtain alloys. As a result, the appearance of the first pharmaceuticals in the near future, the creation of ceramics are noted.

However, you can clearly see the starting point in the history of the emergence of chemistry when you find yourself in the ancient Greek state. It is here that the Sophists in the fifth century of our era explore the new position of man-cosmos, thanks to which they come to the surprising conclusion that to transform the world around us, man needs the means at hand. At the same time, an atomistic picture of the world of Democritus appears, who preached to people that all the objects around us are made up of the smallest particles. Subsequently, these particles will be called atoms.

Of course, in the framework of the ancient world, such a statement was akin to a fantastic idea, thus, few people took Democritus seriously. However, at the turn of the new time, many figures of historical science returned to his theory more than once as the main point in the history of the emergence of chemistry.

The origin of alchemy

Much is known about the Great Alexander, in particular, that he had the largest library of the ancient world. That is why the main scientific center by the second millennium BC is being formed in Alexandria - there is an opinion that the history of organic chemistry began from here. It is in this city that an amazing human activity is born - alchemy.

It is the next stage in the history of chemistry as a science. At this stage, the knowledge of the ancient Greeks and the theoretical information of Plato were completely combined, which, in fact, was reflected in alchemy. Alchemists had a special interest in metals. For these substances, they even developed their own structuring based on celestial objects. Thus, silver was visually depicted as the Moon, iron - in the form of Mars. Such was the history of the development of organic chemistry.

As a result of the fact that the culture of ancient times was completely immersed in religious thinking, and alchemy had its own divine patron - Thoth. At this time, the first works appear that illuminate scientific searches and the place of man in the world. The history of the development of chemistry begins to be enriched with events. The hermit explorer Bolos, originally from the city of Mendes, wrote the treatise "Physics and Mysticism", which was the result of his long wanderings and reflected the description of known metals and precious stones, their properties and practical significance for humans.

The well-known alchemist Zosim Panopolit in his numerous works considered artificial methods for obtaining gold from metals. It was from this moment that the history of the origin of chemistry began to be of a mass nature. Almost everyone started talking about alchemy, various segments of the population became interested in it, and everyone, of course, was attracted by the idea of ​​​​mining gold and eternal life. The history of chemistry, briefly presented in our material, is what all scientists who wanted to achieve something knew in those days.

Amalgam opening

Egyptian researchers went further than many in alchemy, who not only fixed various metals, but also looked for the ores from which they were obtained, that is, they conducted experiments, not only described, but also investigated reality. It was in Egypt that a practical school for amalgam extraction was opened. It was an alloy between mercury and metals. Very soon a special outburst occurred among the alchemists, caused by the achievements of Egyptian researchers. The history of the development of chemistry, briefly reviewed by us, was again rewritten. They began to believe that the element produced by the Egyptians is nothing more than the primary substance, the composition of our world. Around the same time, there were new discoveries in the golden current. It was found that with the help of lead and saltpeter, gold can be made even more beautiful and brighter.

Chemical discoveries in the East

At the next stage of its development, the experience accumulated by the Greek school is transferred to the Arab world. Here comes the real golden heyday, when many Muslim researchers are actively involved in the scientific process. Scientists were able to achieve a number of innovations: phosphorus, antimony, a lot was obtained in the medical business, new types of medicines and potions were developed.

To the alchemical interpretation, which allows you to turn any metal into gold, in this part of the world they made their comments. There was an idea that any substance can be turned into this precious metal. And this can be done by finding a special philosopher's stone. This statement also revived the interest of the population in this discipline, many began to try to study at least briefly the history of chemistry.

At the end of the 9th century, the Arab explorer Jabir ibn Hayyan put forward the mercury-sulfur theory. This theory revised past views on the nature of the origin of metals and made a certain sensation in the alchemical circles not only of the Arab, but also of European schools.

The development of chemistry in the Middle Ages

By the present era, the Christian world still knew little about those currents and progressive ideas that were emerging in the East. However, the religious crusades, in a sense, helped to touch two such different worlds and to accomplish cultural assimilation. At the turn of the XII-XIII centuries, European science assumes a leading position. Chemical research is currently underway. The history of the subject "chemistry" in the medieval period is associated with such personalities as Roger Bacon, Albertus Magnus and Raymond Lully.

Middle Ages - the apogee of religious thinking. The whole life of a person was saturated with faith, such an imprint could not but be superimposed on chemical science. Remarkable is the fact that to discover new substances, to learn their capabilities, to consider ways of using steel in temples and monasteries. So, one of the first significant discoveries, known to this day, was ammonia. As in any previous century, this scientific branch was of little concern to society until gunpowder was discovered in the middle of the 13th century. His discovery is attributed to Roger Bacon. This substance has made a kind of revolution in the mind of man, and subsequently in the military industry.

The sixteenth century was almost entirely devoted to the search for new elements that could be used in medicine. At this time, many ideas are being formed about panaceas, substances that can prolong human life.

The development of chemistry in modern times

A characteristic social feature of the new time is getting rid of theological thinking. In this regard, a whole range of scientific disciplines is being formed. It was at this time that we can talk about the history of chemistry as a science. A unique personality at that time was Robert Boyle, who set himself an unprecedented task - to find as many chemical elements and substances as possible, study their properties and structure previously obtained information.

Another cult personality was Antoine Lavoisier, who by the end of the 18th century was demonstrating to society his theory of oxygen combustion. This is a new level in the development of the chemical industry. A brief history of the development of chemistry, described in his main scientific work "Elementary Physics Course", was written in a lively, simple and accessible language for all people.

Starting from the law of conservation of mass, Antoine creates a table of available chemical elements. Based on this structure, ideas about the nature of a chemical substance change. Awareness of the structure of compounds is very significant, since all life on Earth is associated with their emergence and transformation. At the same time, there is a division of chemical science into two main sections - organic and inorganic chemistry, that is, the chemistry of living and inanimate nature. The history of organic chemistry stands out, is formed separately. Thus, the new time already demonstrates a completely scientific chemistry, which is based on empirical principles and laboratory experiments.

Nineteenth century in the history of the development of chemical science

At the beginning of the nineteenth century, many scholars began to turn their eyes back to ancient thought. So, at the beginning of the 19th century, John Dalton, based on the assumptions of Democritus, puts forward his atomic theory. Observing the processes of transformation of substances, unlike each other, scientists came to the conclusion that absolutely all substances consist of the smallest particles - atoms and molecules. Subsequently, it was discovered that the most important characteristic of these particles is the mass.

At the same time, the basic chemical laws were discovered, which were refined in subsequent centuries, transformed taking into account new knowledge, but nevertheless did not lose their significance in chemical science. Here is a list of these laws:

• constancy of the chemical composition;
• mass conservation;
• multiple and volume ratio.

Avogadro's hypothesis, as well as the gas law formulated a little later, turns into one of the basic laws of physics and chemistry of this century. These two provisions opened the way for establishing a standard scale for atomic masses. Note that these scales are still in use today.

Chemistry in the middle of the 19th century

By the middle of the nineteenth century, scientists had discovered more than fifty chemical elements, calculated their atomic masses, studied the properties and methods of combining with other substances. All this was the result of the discovery of the main chemical law - the periodic law of D. I. Mendeleev. The innovations of this scientist were that the pattern of changes in the properties of chemical elements with an increase in the volume of the mass of atoms was revealed before any explanation of this phenomenon appeared.

To date, the discoveries of Mendeleev have not lost their significance. The discovery of new chemical elements and the conduct of modern research only further strengthened the main positions of the scientist. The periodic table of chemical elements, created on the basis of this law, is the main guide in studying the properties of any chemical element.

Chemistry at the beginning of the 20th century

At the beginning of the twentieth century, a real revolution took place in the chemical arena. At this time, the basic provisions of quantum mechanics were formed and the structure of the atom was determined. These discoveries were a fundamental link in understanding the meaning of the periodic law and the structure of matter in general. A characteristic feature of this time is the idea of ​​close interaction between the sciences of physics and chemistry. After all, the differences between these natural sciences appear only within the framework of the studied phenomena.

The modern stage of development of chemistry

Today, knowledge about chemical elements and their structure helps to explain and predict the properties of molecules and natural substances, which are a collection of a large number of moving particles. The technical level allows you to study various transformations of molecules. In recent years, it has become possible to use computer simulation based on quantum mechanics calculations to determine the structure of a chemical compound of a substance, the connection mechanisms and methods of particle movement, which are difficult to experimentally fix.

It is necessary to mention that today the main goal facing chemical science is the study of the process: whether this chemical reaction will take place or not, and if it does, what will be the result and what are the optimal conditions so that the efficiency of the reaction being carried out is as more, and the speed of the process is acceptable? Studying the rate of the reaction is very important both to identify the optimal conditions for the reaction, and in order to know in advance, before the reaction, approximately the result.

So why do we need chemistry? Today, one cannot do without basic knowledge of this scientific discipline. Knowledge of general principles and chemical laws is necessary for a scientist working in any branch of chemical knowledge, whether it is the study of processes occurring in the bowels of the Earth, the production of polymeric materials, or the human body.

Chemistry is the science of the composition, structure and properties of substances. Chemistry studies the process of transformation of these substances, as well as the laws by which these transformations occur.

Man began to engage in chemical activity long before our era. This happened at a time when people learned how to get metals. Then the production of ceramics, glass, tanning of leather, dyeing of fabrics, the creation of medicines, and the manufacture of cosmetics began.

As early as 300 BC, the Egyptian Zosima created an encyclopedia that consisted of 28 volumes. These volumes collected knowledge on the mutual transformations of substances over the past 500-600 years.

Alchemy

The emergence of alchemy can be considered the initial stage in the development of chemistry. Alchemy was based on the ideas of the ancient Greek philosophers Empedocles, Plato and Aristotle about the elements of nature and their mutual transformation. It was believed that there were four principles: earth, water, air and fire. And they are able to pass into each other, since each of them is one of the states of a single primary matter. And all substances are formed as a result of a combination of these initial principles.

Alchemists transformed one substance into another. They believed that metals could also undergo similar transformations. Many scientists were busy looking for the "philosopher's stone", which was supposed to turn base metals into gold. And during these searches in their laboratories, alchemists learned how to obtain alkalis, many salts, sulfuric and nitric acids, and ethanol. With the help of these substances, they could act on other substances. In the middle of the XIII century, European alchemists received gunpowder.

It should be said that alchemy in Europe was banned. Both the church and the secular authorities forbade the practice of alchemy. But, despite this, alchemy was popular until the beginning of the XVI century.

The development of chemistry as a science

In the 16th century, the Irish scientist Boyle freed chemistry from alchemy. He suggested that all substances are composed of chemical elements that cannot be broken down into simpler parts. We can say that since that time chemistry has become a separate science.

At the end of the 17th - beginning of the 18th centuries, the theory of the German chemist E.G. Stahl, explaining the phenomena of combustion, oxidation and reduction of metals. But this theory was recognized as erroneous in the middle of the 18th century by the French physicist Lavoisier, who established the role of oxygen in these processes. M.V. Lomonosov discovered the law of conservation of the mass of matter in chemical processes.

From the end of the 18th century to the middle of the 19th century, a whole series of stoichiometric laws was discovered that established quantitative relationships (mass and volume) between reactants and reaction products. Avogadro's law, the laws of conservation of mass, equivalents, constancy of composition, volume ratios, multiple ratios are the laws underlying stoichiometry. These laws made it possible to create rules for compiling chemical equations and formulas. It was after the experimental confirmation of these laws that chemistry was formed as a science. The atomic and molecular concept of the structure of matter, confirmed by the theory of the structure of chemical compounds, created by A.M. Butlerov. D.M. Mendeleev discovered the periodic law.

After the discovery of the electron and radioactivity at the end of the 19th century, the theory of heteropolar (ionic) bonding and the theory of homeopolar (covalent) bonding were developed at the beginning of the 20th century. In 1927, the development of the quantum mechanical theory of chemical bonding began. Mendeleev's doctrine of the periodicity of chemical elements has been confirmed. It became possible to predict the properties of substances. Physical and mathematical methods began to be widely used for various calculations in the field of chemistry. New physicochemical methods of analysis have appeared: electronic and vibrational spectrometry, magnetochemistry, etc.

In the twentieth century, thanks to the achievements of chemical science, it became possible to obtain substances with desired properties: synthetic antibiotics, synthetic polymers, plastics, various building materials, fabrics, etc.

Modern chemistry closely cooperates with other sciences. As a result, completely new branches of chemistry appeared: biochemistry, geochemistry, colloid chemistry, crystal chemistry, electrochemistry, chemistry of macromolecular compounds, etc.

An important direction of modern chemistry is the production of cheap fuel, which creates an alternative to the main modern energy sources - oil and gas.

Precise modern instruments and computers have greatly simplified research and mathematical calculations in the field of chemistry, increased their accuracy, speed and reduced cost.

Chemistry is a very ancient science.

Chemical production existed already for 3-4 thousand years BC. e. In ancient Egypt, they knew how to smelt metals (iron, lead, copper, tin, antimony) from ores, obtain their alloys, used gold, silver, produced glass, ceramics, pigments, paints, perfumes, the Egyptians were unsurpassed builders and sculptors (Fig. 17 ).

The first chemists were the Egyptian priests. They owned many hitherto unsolved chemical secrets. These, for example, include techniques for embalming the bodies of dead pharaohs and nobles, as well as methods for obtaining some paints. Thus, the blue and blue colors of the vessels found during excavations, made by ancient Egyptian craftsmen, continue to be bright, although several thousand years have passed since their manufacture.

Rice. 17.
Chemistry in Ancient Egypt:
a - embalming; b - the death mask of the Egyptian pharaoh Tutankhamun; c - a sculpture made by an ancient master

Some chemical industries existed in antiquity in Greece, Mesopotamia, India, and China.

In the III century. BC e. significant experimental material has already been collected and described. For example, in the famous Library of Alexandria, which was considered one of the seven wonders of the world and consisted of 700 thousand handwritten books, many works on chemistry were also kept. They described processes such as calcination, sublimation, distillation, filtration, etc.

Separate chemical information accumulated over many centuries made it possible to make some generalizations about the nature of substances and phenomena. For example, the Greek philosopher Democritus, who lived in the V century. BC e., for the first time expressed the idea that all bodies consist of the smallest, invisible, indivisible and eternally moving solid particles of matter, which he called atoms. Aristotle in the 4th century BC e. believed that the basis of the surrounding nature are four elements, which are characterized by four basic qualities: warmth and cold, dryness and humidity (Fig. 18). These four qualities, in his opinion, could be separated from the elements or added to them in any quantity.

Rice. eighteen.
Aristotle's diagram "The Four Elements and Their Interaction"

The teaching of Aristotle was the ideological basis for the development of a separate era in the history of chemistry, the era of the so-called alchemy. In the middle of the 7th century n. e. the knowledge of the Egyptians and Greeks in the field of chemistry was adopted by the Arabs; they borrowed much information on chemistry from the Syrians and the Chinese.

The origin of the word chemistry is debatable. Hemi - in Coptic means "black, secret". This word for the peoples who inhabited the desert coincided with the designation of Egypt itself, for the black, fertile land of the Nile Valley was very different from the yellow soil of the desert. Thus, for the Arabs, chemistry became the science of the black earth. The Arabs provided this word with their Arabic prefix al, and thus the word alchemy was formed. Alchemy is the medieval name given to chemistry by the Arabs. However, perhaps the concept of something black referred not only to the color of the soil, but also to the very essence of this science - dark and mysterious in those days.

Another interpretation of the word "chemistry" comes from the Greek verb hyuma - "to pour out", since it is associated with metallurgy - one of the first branches of chemistry in time.

As you can see, finding out the etymology (origin) of chemical terms has a deep meaning - it helps to understand either the history or the practical meaning of what the chemical term denotes.

The goal of alchemy is to find ways to transform base metals into noble ones (gold and silver) with the help of an imaginary substance - the philosopher's stone. Many alchemists pursued a fruitless search for the philosopher's stone, which they believed could also lengthen human life, provide immortality, or cure disease. In search of the philosopher's stone, alchemists discovered many new substances, developed methods for their purification, and created some chemical equipment (Fig. 19). Most of the achievements of alchemists could not be used: they kept their methods secret, encrypted descriptions of the substances obtained and the experiments carried out, as they pursued the goals of enrichment.

Rice. 19.
In the alchemy laboratory

At the beginning of the XVI century. n. e. alchemists began to use the data they received for the needs of industry and medicine. The reformer in the field of mining and metallurgy was Agricola, and in the field of medicine - Paracelsus, who pointed out that "the purpose of chemistry is not to make gold and silver, but to make medicines."

It should be noted that alchemy was not particularly widespread in Russia, although the treatises of alchemists were known, and some were even translated into Church Slavonic. Moreover, the German alchemist Van Geyden offered the Moscow court his services in preparing the philosopher's stone - how "to make silver and gold from lead and tin, iron, copper and mercury, and what is decent for that business," but Tsar Mikhail Fedorovich, after "questioning" these rejected offers.

The fact that alchemy did not become widespread in Russia is explained by the fact that money and gold in Russia began to be widely used later in comparison with Western countries, since there was a later transition from quitrent to cash rent. In addition, mysticism, the vagueness of the goals and the unreality of the methods of alchemy were contrary to the common sense and efficiency of the Russian people.

Chemistry in Russia developed mainly in its own way. Metals were smelted in Kievan Rus, glass, salts, paints, fabrics were produced. Under Ivan the Terrible, a pharmacy was opened in Moscow in 1581. Under Peter I, vitriol and alum factories were built, the first chemical manufactories, and there were already eight pharmacies in Moscow. The further development of chemistry in Russia is associated with the work of M. V. Lomonosov.

M. V. Lomonosov conducted experiments with the incandescence of metals in sealed vessels. By these experiments, he proved that the mass of the substances obtained as a result of the experiment was exactly the same as the mass of the substances that entered into the reaction. On the basis of similar experiments with accurate weighing of substances before and after the reaction, in 1748 M.V. Lomonosov for the first time formulated the most important law of chemistry - the law of conservation of the mass of substances in chemical reactions.

Somewhat later, the French scientist Antoine Lavoisier, conducting similar experiments using precise weighing methods, came to the same conclusion.

A significant contribution to the development of chemistry was made by the outstanding Russian scientists A. M. Butlerov and D. I. Mendeleev.

A. M. Butlerov in 1861 created a theory of the structure of organic compounds, which made it possible to bring into the system knowledge about a huge number of organic compounds and without which modern successes in the creation of new polymeric materials would be unthinkable. The ideas of A. M. Butlerov were continued by outstanding Russian scientists: V. V. Markovnikov, A. A. Zaitsev, A. E. Favorsky, E. E. Vagner, S. V. Lebedev, N. D. Zelinsky and many others .

D. I. Mendeleev, on the basis of the Periodic Law (the fundamental law of natural science) discovered by him in 1869, created a coherent scientific classification of chemical elements - the Periodic Table of Chemical Elements, named after him.

Work with computer

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Questions and tasks

1. After studying the origin of the word chemistry, write a story about chemistry and its significance in the history of ancient civilizations.
2. Formulate the law of conservation of mass of substances. Think about why, when a candle burns, its mass gradually decreases. Does this observation contradict the law of conservation of mass of substances?
3. What traits of the Russian character, in your opinion, explain the fact that the greatest generalizations in chemistry were made by Russian chemists: M. V. Lomonosov discovered the law of conservation of mass of substances, A. M. Butlerov created the theory of the structure of organic compounds, and D. I. Q. Mendeleev formulated the Periodic Law and developed the Periodic Table of Chemical Elements?
4. Prepare short reports (optional) about the life and work of M. V. Lomonosov, A. M. Butlerov, D. I. Mendeleev,
5. Name literary works that describe the experiments of alchemists and the philosopher's stone.

CHEMISTRY HISTORY
The article traces the development of chemistry from its very origins, from the time when a person learned to extract and maintain fire and smelt metals from ores with it, then through the era of antiquity and the Middle Ages to our time - the period of the triumph of chemical science and technology.
ORIGINS OF CHEMISTRY
Chemistry of antiquity. Chemistry, the science of the composition of substances and their transformations, begins with the discovery by man of the ability of fire to change natural materials. Apparently, people knew how to smelt copper and bronze, fire clay products, and get glass as far back as 4000 BC. By the 7th c. BC. Egypt and Mesopotamia became centers of dye production; In the same place, gold, silver and other metals were obtained in their pure form. From about 1500 to 350 BC distillation was used to produce dyes, and metals were smelted from ores by mixing them with charcoal and blowing air through the burning mixture. The very procedures for the transformation of natural materials were given a mystical meaning.
Greek natural philosophy. These mythological ideas penetrated into Greece through Thales of Miletus (c. 625 - c. 547 BC), who erected all the variety of phenomena and things to a single element - water. However, Greek philosophers were not interested in the methods of obtaining substances and their practical use, but mainly in the essence of the processes taking place in the world. Thus, the ancient Greek philosopher Anaximenes (585-525 BC) argued that the fundamental principle of the Universe is air: when rarefied, air turns into fire, and as it thickens, it becomes water, then earth and, finally, stone. Heraclitus of Ephesus (late 6th - early 5th centuries BC) tried to explain natural phenomena by postulating fire as the first element.
Four primary elements. These ideas were combined in the natural philosophy of Empedocles from Agrigent (490-430 BC) - the creator of the theory of the four principles of the universe. In various versions, his theory dominated the minds of people for more than two millennia. According to Empedocles, all material objects are formed by combining the eternal and unchanging elements-elements - water, air, earth and fire - under the influence of the cosmic forces of love (attraction) and hatred (repulsion). The theory of the elements of Empedocles was accepted and developed first by Plato (427-347 BC), who specified that the immaterial forces of good and evil can turn these elements one into another, and then by Aristotle (384-322 BC). According to Aristotle, elements-elements are not material substances, but carriers of certain qualities - heat, cold, dryness and humidity. This view was transformed into the idea of ​​the four "juices" of Galen (129-200 AD) and dominated science until the 17th century. Another important question that occupied the Greek natural philosophers was the question of the divisibility of matter. The founders of the concept, later called "atomistic", were Leucippus (c. 500-440 BC), his student Democritus (c. 470-360 BC) and Epicurus (c. 342-270 BC). .e.). According to their teaching, only emptiness and atoms exist - indivisible material elements, eternal, indestructible, impenetrable, differing in shape, position in emptiness and size; all bodies are formed from their "whirlwind". The atomistic theory remained unpopular for two millennia after Democritus, but did not disappear completely. One of its adherents was the ancient Greek poet Titus Lucretius Car (95-55 BC), who expounded the views of Democritus and Epicurus in the poem On the Nature of Things (De Rerum Natura).
Alchemy. Alchemy is the art of improving matter through the transformation of metals into gold and the improvement of man by creating the elixir of life. In an effort to achieve the most attractive goal for them - the creation of incalculable wealth - alchemists solved many practical problems, discovered many new processes, observed various reactions, contributing to the formation of a new science - chemistry.

Hellenistic period. Egypt was the cradle of alchemy. The Egyptians brilliantly mastered applied chemistry, which, however, was not singled out as an independent field of knowledge, but was included in the "sacred secret art" of the priests. As a separate field of knowledge, alchemy appeared at the turn of the 2nd and 3rd centuries. AD After the death of Alexander the Great (323 BC), his empire collapsed, but the influence of the Greeks spread over the vast territories of the Near and Middle East. Alchemy reached a particularly rapid flowering in 100-300 AD. in Alexandria. Around 300 AD Egyptian Zosima wrote an encyclopedia - 28 books covering all the knowledge of alchemy for the previous 5-6 centuries, in particular information about the mutual transformations (transmutations) of substances.
Alchemy in the Arab world. Having conquered Egypt in the 7th century, the Arabs assimilated the Greco-Oriental culture, which was preserved for centuries by the Alexandrian school. Imitating the ancient rulers, the caliphs began to patronize the sciences, and in the 7th-9th centuries. the first chemists appeared. The most talented and famous Arab alchemist was Jabir ibn Hayyan (late 8th century), who later became known in Europe under the name Geber. Jabir believed that sulfur and mercury are two opposite principles from which seven other metals are formed; gold is most difficult to form: this requires a special substance, which the Greeks called xerion - "dry", and the Arabs changed it to al-iksir (this is how the word "elixir" appeared). The elixir was supposed to have other miraculous properties: to cure all diseases and give immortality. Another Arab alchemist, ar-Razi (c. 865-925) (known in Europe as Razes) also practiced medicine. So, he described the method of preparing plaster and the method of applying a bandage to the fracture site. However, the most famous physician was the Bukharan Ibn Sina (c. 980-1037), also known as Avicenna. His writings served as a guide for physicians for many centuries.
Alchemy in Western Europe. The scientific views of the Arabs penetrated medieval Europe in the 12th century. through North Africa, Sicily and Spain. The works of Arab alchemists were translated into Latin and then into other European languages. At first, alchemy in Europe relied on the work of such luminaries as Jabir, but three centuries later there was renewed interest in the teachings of Aristotle, especially in the writings of the German philosopher and Dominican theologian, who later became a bishop and professor at the University of Paris, Albert the Great (c. 1200-1280 ) and his student Thomas Aquinas. Convinced of the compatibility of Greek and Arabic science with Christian doctrine, Albertus Magnus encouraged their introduction into scholastic curricula. In 1250 Aristotle's philosophy was introduced into the teaching curriculum at the University of Paris. The English philosopher and naturalist, Franciscan monk Roger Bacon (1214-1294), who anticipated many later discoveries, was also interested in alchemical problems; he studied the properties of saltpeter and many other substances, found a way to make black powder. Other European alchemists include Arnaldo da Villanova (1235-1313), Raymond Lull (1235-1313), Basil Valentine (15th-16th century German monk).
Achievements of alchemy. The development of crafts and trade, the rise of cities in Western Europe in the 12th-13th centuries. accompanied by the development of science and the emergence of industry. Alchemists' recipes were used in technological processes such as metalworking. During these years, systematic searches for methods for obtaining and identifying new substances began. There are recipes for the production of alcohol and improvements in the process of its distillation. The most important achievement was the discovery of strong acids - sulfuric, nitric. Now European chemists were able to carry out many new reactions and obtain substances such as salts of nitric acid, vitriol, alum, salts of sulfuric and hydrochloric acids. The services of alchemists, who were often skilled doctors, were used by the highest nobility. It was also believed that alchemists possessed the secret of transmuting ordinary metals into gold.

IN THE "LABORATORY" OF THE ALCHEMIST

By the end of the 14th century the interest of alchemists in the transformation of some substances into others gave way to an interest in the production of copper, brass, vinegar, olive oil and various medicines. In the 15-16 centuries. the experience of alchemists was increasingly used in mining and medicine.
THE ORIGIN OF MODERN CHEMISTRY
The end of the Middle Ages was marked by a gradual departure from the occult, a decline in interest in alchemy and the spread of a mechanistic view of the structure of nature.
Iatrochemistry. Completely different views on the goals of alchemy were held by Paracelsus (1493-1541). Under such a name chosen by him ("superior to Celsus"), the Swiss doctor Philipp von Hohenheim went down in history. Paracelsus, like Avicenna, believed that the main task of alchemy was not the search for ways to obtain gold, but the manufacture of medicines. He borrowed from the alchemical tradition the doctrine that there are three main parts of matter - mercury, sulfur, salt, which correspond to the properties of volatility, combustibility and hardness. These three elements form the basis of the macrocosm (Universe) and are associated with the microcosm (man) formed by the spirit, soul and body. Turning to the definition of the causes of diseases, Paracelsus argued that fever and plague come from an excess of sulfur in the body, paralysis occurs with an excess of mercury, and so on. The principle that all iatrochemists adhered to was that medicine is a matter of chemistry, and everything depends on the ability of the doctor to isolate pure principles from impure substances. Under this scheme, all functions of the body were reduced to chemical processes, and the task of the alchemist was to find and prepare chemicals for medical purposes. The main representatives of the iatrochemical direction were Jan Helmont (1577-1644), a doctor by profession; Francis Silvius (1614-1672), who enjoyed great fame as a physician and eliminated "spiritual" principles from the iatrochemical doctrine; Andreas Libavius ​​(c. 1550-1616), physician from Rothenburg Their research contributed greatly to the formation of chemistry as an independent science.
mechanical philosophy. With the diminishing influence of iatrochemistry, natural philosophers turned again to the teachings of the ancients about nature. Foreground in the 17th century. atomistic (corpuscular) views came out. One of the most prominent scientists - authors of the corpuscular theory - was the philosopher and mathematician Rene Descartes (1596-1650). He outlined his views in 1637 in his Discourse on Method. Descartes believed that all bodies "consist of numerous small particles of various shapes and sizes, ... which are not so closely adjacent to each other that there are no gaps around them; these gaps are not empty, but filled with ... rarefied matter." Descartes did not consider his "small particles" to be atoms; indivisible; he stood on the point of view of the infinite divisibility of matter and denied the existence of emptiness. One of the most prominent opponents of Descartes was the French physicist and philosopher Pierre Gassendi (1592-1655). Atomism Gassendi was essentially a retelling of the teachings of Epicurus, however, unlike the latter, Gassendi recognized the creation of atoms by God; he believed that God created a certain number of indivisible and impenetrable atoms, of which all bodies are composed; there must be an absolute void between the atoms. In the development of chemistry in the 17th century. a special role belongs to the Irish scientist Robert Boyle (1627-1691). Boyle did not accept the statements of the ancient philosophers, who believed that the elements of the universe can be established speculatively; this is reflected in the title of his book The Skeptical Chemist. Being a supporter of the experimental approach to the definition of chemical elements (which was eventually adopted), he did not know about the existence of real elements, although one of them - phosphorus - almost discovered himself. Boyle is usually credited with introducing the term "analysis" into chemistry. In his experiments on qualitative analysis, he used various indicators, introduced the concept of chemical affinity. Based on the works of Galileo Galilei (1564-1642) and Evangelista Torricelli (1608-1647), as well as Otto Guericke (1602-1686), who demonstrated "Magdeburg hemispheres" in 1654, Boyle described the air pump he designed and experiments to determine the elasticity of air at using the U-tube. As a result of these experiments, the well-known law on the inverse proportionality of the volume and pressure of air was formulated. In 1668 Boyle became an active member of the newly organized Royal Society of London, and in 1680 he was elected its president.
Technical chemistry. Scientific advances and discoveries could not but affect technical chemistry, elements of which can be found in the 15th-17th centuries. In the middle of the 15th century blower technology was developed. The needs of the military industry stimulated work to improve the technology of gunpowder production. During the 16th century the production of gold doubled and the production of silver increased ninefold. There are fundamental works on the production of metals and various materials used in construction, in the manufacture of glass, dyeing of fabrics, for the preservation of food products, and leather dressing. With the expansion of the consumption of alcoholic beverages, distillation methods are being improved, new distillation apparatuses are being designed. Numerous production laboratories appear, primarily metallurgical ones. Among the chemical technologists of that time, we can mention Vannoccio Biringuccio (1480-1539), whose classic work On Pyrotechnics was published in Venice in 1540 and contained 10 books dealing with mines, testing minerals, preparing metals, distillation, military art and fireworks. Another famous treatise, On Mining and Metallurgy, was written by George Agricola (1494-1555). Mention should also be made of Johann Glauber (1604-1670), a Dutch chemist, creator of Glauber's salt.
XVIII CENTURY
Chemistry as a scientific discipline. From 1670 to 1800, chemistry received official status in the curricula of leading universities along with natural philosophy and medicine. In 1675, the textbook by Nicolas Lemery (1645-1715) A Course in Chemistry appeared, which gained immense popularity, 13 of its French editions were published, and in addition, it was translated into Latin and many other European languages. In the 18th century scientific chemical societies and a large number of scientific institutes are being created in Europe; their research is closely related to the social and economic needs of society. Practicing chemists appear who are engaged in the manufacture of devices and the preparation of substances for industry.
Phlogiston theory. In the writings of chemists of the second half of the 17th century. much attention was paid to interpretations of the combustion process. According to the ideas of the ancient Greeks, everything that is capable of burning contains the element of fire, which is released under appropriate conditions. In 1669 the German chemist Johann Joachim Becher (1635-1682) attempted to rationalize combustibility. He suggested that solids consist of three types of "earth", and he took one of the types, which he called "fat earth", for the "principle of combustibility". A follower of Becher, the German chemist and physician Georg Ernst Stahl (1659-1734) transformed the concept of "fat earth" into a generalized doctrine of phlogiston - "the beginning of combustibility". According to Stahl, phlogiston is a certain substance contained in all combustible substances and released during combustion. Stahl argued that the rusting of metals is similar to the combustion of wood. Metals contain phlogiston, but rust (dross) no longer contains phlogiston. This gave an acceptable explanation for the process of turning ores into metals: an ore, the content of phlogiston in which is insignificant, is heated on charcoal rich in phlogiston, and the latter turns into ore. Coal turns into ash, and ore into a metal rich in phlogiston. By 1780, the phlogiston theory was almost universally accepted by chemists, although it did not answer a very important question: why does iron become heavier when it rusts, although phlogiston escapes from it? Chemists of the 18th century. this contradiction did not seem so important; the main thing, in their opinion, was to explain the reasons for the change in the appearance of substances. In the 18th century many chemists worked, whose scientific activity does not fit into the usual schemes for considering the stages and directions of the development of science, and among them a special place belongs to the Russian scientist-encyclopedist, poet, champion of education Mikhail Vasilyevich Lomonosov (1711-1765). With his discoveries, Lomonosov enriched almost all areas of knowledge, and many of his ideas were more than a hundred years ahead of the science of that time. In 1756, Lomonosov carried out the famous experiments on firing metals in a closed vessel, which provided indisputable evidence of the conservation of matter in chemical reactions and the role of air in combustion processes: even before Lavoisier, he explained the observed increase in weight during firing of metals by combining them with air. In contrast to the prevailing ideas about caloric, he argued that thermal phenomena are due to the mechanical movement of material particles. He explained the elasticity of gases by the movement of particles. Lomonosov distinguished between the concepts of "corpuscle" (molecule) and "element" (atom), which was generally recognized only in the middle of the 19th century. Lomonosov formulated the principle of the conservation of matter and motion, excluded phlogiston from the list of chemical agents, laid the foundations of physical chemistry, and created a chemical laboratory at the St. Petersburg Academy of Sciences in 1748, in which not only scientific work was carried out, but also practical classes for students. He conducted extensive research in areas of knowledge adjacent to chemistry - physics, geology, etc.
Pneumatic chemistry. The shortcomings of the phlogiston theory were most clearly revealed during the development of the so-called. pneumatic chemistry. The largest representative of this direction was R. Boyle: he not only discovered the gas law, which now bears his name, but also designed apparatus for collecting air. Chemists have received the most important tool for isolating, identifying and studying various "airs". An important step was the invention by the English chemist Stephen Hales (1677-1761) of the "pneumatic bath" in the early 18th century. - a device for trapping gases released when a substance is heated, into a vessel with water, lowered upside down into a bath of water. Later, Hales and Henry Cavendish (1731-1810) established the existence of certain gases ("airs") that differ in their properties from ordinary air. In 1766, Cavendish systematically studied the gas formed during the interaction of acids with certain metals, later called hydrogen. A great contribution to the study of gases was made by the Scottish chemist Joseph Black (1728-1799). He took up the study of gases released by the action of acids on alkalis. Black found that the mineral calcium carbonate, when heated, decomposes with the release of gas and forms lime (calcium oxide). The liberated gas (carbon dioxide - Black called it "bound air") could be recombined with lime to form calcium carbonate. Among other things, this discovery established the inseparability of bonds between solid and gaseous substances.
chemical revolution. Joseph Priestley (1733-1804), a Protestant priest who was passionate about chemistry, achieved great success in isolating gases and studying their properties. Near Leeds (England), where he served, there was a brewery, from where it was possible to obtain large quantities of "bound air" (now we know that it was carbon dioxide) for experiments. Priestley discovered that gases could dissolve in water and tried to collect them not over water, but over mercury. So he managed to collect and study nitric oxide, ammonia, hydrogen chloride, sulfur dioxide (of course, these are their modern names). In 1774, Priestley made his most important discovery: he isolated a gas in which substances burned especially brightly. Being a supporter of the theory of phlogiston, he called this gas "dephlogisticated air". The gas discovered by Priestley seemed to be the opposite of "phlogisticated air" (nitrogen) isolated in 1772 by the English chemist Daniel Rutherford (1749-1819). In "phlogisticated air" the mice died, while in "dephlogisticated" they were very active. (It should be noted that the properties of the gas isolated by Priestley were described by the Swedish chemist Carl Wilhelm Scheele (1742-1786) as early as 1771, but his message, due to the negligence of the publisher, appeared in print only in 1777.) The great French chemist Antoine Laurent Lavoisier (1743-1794 ) immediately appreciated the significance of Priestley's discovery. In 1775, he prepared an article where he argued that air is not a simple substance, but a mixture of two gases, one of them is Priestley's "dephlogisticated air", which combines with burning or rusting objects, passes from ores to charcoal and is necessary for life. Lavoisier called it oxygen, oxygen, i.e. "producer of acids". The second blow to the theory of elemental elements was dealt after it became clear that water is also not a simple substance, but a product of the combination of two gases: oxygen and hydrogen. All these discoveries and theories, having done away with the mysterious "elements", led to the rationalization of chemistry. Only those substances that can be weighed or whose quantity can be measured in some other way have come to the fore. During the 80s of the 18th century. Lavoisier, in collaboration with other French chemists - Antoine Francois de Fourcroix (1755-1809), Guiton de Morveau (1737-1816) and Claude Louis Berthollet (1748-1822) - developed a logical system of chemical nomenclature; more than 30 simple substances were described in it, indicating their properties. This work, Method of Chemical Nomenclature, was published in 1787. The revolution in the theoretical views of chemists, which took place at the end of the 18th century. as a result of the rapid accumulation of experimental material under the dominance of the phlogiston theory (albeit independently of it), is usually called the "chemical revolution".
NINETEENTH CENTURY
Composition of substances and their classification. Lavoisier's successes showed that the use of quantitative methods can help in determining the chemical composition of substances and elucidating the laws of their association.
Atomic theory. The English chemist John Dalton (1766-1844), like the ancient atomists, proceeded from the concept of the corpuscular structure of matter, but, based on the concept of Lavoisier's chemical elements, he accepted that "atoms" (this term Dalton retained as a tribute to Democritus) of a given element are identical and are characterized, among other properties, by the fact that they have a certain weight, which he called atomic. Dalton discovered that two elements can combine with each other in different ratios, and each new combination of elements gives a new connection. In 1803 these results were generalized in the form of the law of multiple ratios. In 1808, Dalton's work, The New System of Chemical Philosophy, was published, in which he detailed his atomic theory. In the same year, the French chemist Joseph Louis Gay-Lussac (1778-1850) published the assumption that the volumes of gases that react with each other are related to each other as simple multiples (the law of volume ratios). Unfortunately, Dalton failed to see in Gay-Lussac's conclusions anything but an obstacle to the development of his theory, although these conclusions could be very fruitful in determining the relative atomic weights.
chemical affinity. Throughout the 17th century chemists, speaking of "affinity" - the tendency of atoms to form compounds - followed the ideas of Becher and Stahl, who classified all substances according to their ability to react with specific acids. The study of the affinity and composition of various types of substances took a different course at the beginning of the 19th century. with the discovery of a new analytical method. In 1807, the English chemist Humphry Davy (1778-1829) passed an electric current from a battery of 250 metal plates through molten potash (potassium carbonate) and obtained small balls of the metal, later called potassium, and then isolated sodium from soda in the same way. Davy suggested that chemical affinity comes down to the electrification of atoms upon contact. The Swedish chemist Jens Jakob Berzelius (1779-1848) refined and developed the idea of ​​the atom and electrical affinity, proposing the first concept of chemical interaction - the electrochemical theory. Berzelius believed that since salts in solution decompose into negative and positive components under the action of an electric current, all compounds must consist of positive and negative parts - radicals (the dualistic theory of Berzelius). Oxygen is the most electronegative element, and those elements that form compounds with the properties of bases with it are electropositive, and those that form substances with acidic properties are electronegative. In accordance with this, Berzelius received a scale of elements, the first member of which was oxygen, followed by sulfur, nitrogen, phosphorus, etc. with the transition through hydrogen to sodium, potassium and other metals. By the 1840s, however, it became clear that the electrochemical theory could not explain the existence of simple diatomic molecules (such as O2 and H2) or the replacement of hydrogen (positive affinity) by chlorine (negative affinity).
Classification by atomic weight. From the time of Dalton until 1860 there was no precise definition of atomic weight in chemistry. The "equivalent weights" system proposed by the English chemist William Wollaston (1766-1828) relied on ratios in which elements could be combined and each chemist could make his own list of atomic weights. There was no starting point for creating a system of elements and no agreement on how to express the composition of compounds. In 1860, at the first International Chemical Congress in Karlsruhe (Germany), the Italian chemist Stanislao Cannizzaro (1826-1910) again brought to life the forgotten hypothesis of his compatriot Amedeo Avogadro (1776-1856), who, based on the discovery of the law of volumetric ratios by Gay-Lussac, suggested that equal volumes of gases contain the same number of molecules. Cannizzaro argued that with the help of Avogadro's hypothesis, one can distinguish between the concepts of "atomic weight" and "molecular weight" for gaseous elements and clarify the question of atomic weights in general. In 1869, the great Russian chemist Dmitry Ivanovich Mendeleev, who was present at the congress in Karlsruhe and heard Cannizzaro's report, published his periodic table. He arranged all the known elements in accordance with the increase in their atomic weight and divided them into periods and groups corresponding to a change in valence. Empty spaces were left in the table for items not yet discovered; Mendeleev even assigned names to some of them (ekabor, ekaaluminum and ekasilicon; the prefix "eka" means "one and the same"). The remarkable accuracy of the periodic law was demonstrated by the discoveries of gallium in 1875, identical in properties to ekaaluminum, scandium (ecabor) in 1879, and germanium (eca-silicon) in 1886.
Organic chemistry. Throughout the 18th century in the question of the chemical relationships between organisms and substances, scientists were guided by the doctrine of vitalism - a doctrine that considered life as a special phenomenon, subject not to the laws of the universe, but to the influence of special vital forces. This view was inherited by many scientists of the 19th century, although its foundations were shaken as early as 1777, when Lavoisier suggested that respiration is a process analogous to combustion. The first experimental evidence of the unity of the inorganic and organic worlds was obtained at the beginning of the 19th century. In 1828, the German chemist Friedrich Wöhler (1800-1882), heating ammonium cyanate (this compound was unconditionally considered an inorganic substance), obtained urea, a waste product of humans and animals. In 1845 Adolf Kolbe (1818-1884), a student of Wöhler, synthesized acetic acid from the starting elements carbon, hydrogen and oxygen. In the 1850s, the French chemist Pierre Berthelot (1827-1907) began systematic work on the synthesis of organic compounds and obtained methyl and ethyl alcohols, methane, benzene, and acetylene. A systematic study of natural organic compounds has shown that they all contain one or more carbon atoms, and very many contain hydrogen atoms. As a result of all these studies, the German chemist Friedrich August Kekule (1829-1896) in 1867 defined organic chemistry as the chemistry of carbon compounds. The new approach to organic analysis was summarized by the German chemist Justus Liebig (1803-1873) - the creator of the famous research and teaching laboratory at the University of Giessen. In 1837, Liebig, together with the French chemist Jean Baptiste Dumas (1800-1884), refined the concept of a radical as a specific, unchanged group of atoms that is part of many organic compounds (an example is the methyl radical CH3). It became clear that the structure of large molecules could be determined only by establishing the structure of a certain number of radicals.
Type theory. The discovery and isolation of a huge number of complex carbon-containing compounds sharply raised the question of the composition of their molecules and led to the need to revise the existing classification system. By the 1840s, chemists realized that Berzelius' dualistic ideas only applied to inorganic salts. In 1853 an attempt was made to classify all organic compounds by type. A generalized "theory of types" was proposed by the French chemist Charles Frédéric Gérard (1816-1856), who believed that the combination of different groups of atoms is determined not by the electric charge of these groups, but by their specific chemical properties. Gerard identified four main types of atomic groups, of which, in his opinion, all compounds, both organic and inorganic, are composed.
Structural chemistry. In 1857, Kekule, proceeding from the theory of valency (by valency was understood as the number of hydrogen atoms that combine with one atom of a given element), suggested that carbon is tetravalent and therefore can combine with four other atoms, forming long chains - straight or branched. Therefore, organic molecules began to be depicted not as combinations of radicals, but as structural formulas - atoms and bonds between them. By the 1860s, the work of Kekule and the Russian chemist Alexander Mikhailovich Butlerov (1828-1886) laid the foundation for structural chemistry, which makes it possible to explain the properties of substances based on the arrangement of atoms in their molecules. In 1874 the Danish chemist Jacob van't Hoff (1852-1911) and the French chemist Joseph Achille Le Bel (1847-1930) extended this idea to the arrangement of atoms in space. They believed that molecules are not flat, but three-dimensional structures. This concept made it possible to explain many well-known phenomena, such as spatial isomerism, the existence of molecules of the same composition but with different properties. The data of Louis Pasteur (1822-1895) on the isomers of tartaric acid fit very well into it. By the end of the 19th century the ideas of structural chemistry were supported by data obtained by spectroscopic methods. These methods made it possible to obtain information about the structure of molecules based on their absorption spectra. By 1900, the concept of a three-dimensional organization of molecules - both complex organic and inorganic - was accepted by almost all scientists.
Chemical Technology. Advances in organic chemistry stimulated the rapid development of the chemical industry, primarily in Germany. A technology for the production of sulfuric acid was developed, on the basis of which explosives, dyes and soda, necessary for the production of bleaches and soaps. A very important role in the development of chemical technology was played by the work of Liebig and a whole galaxy of his students. As a result of their activities, chemical fertilizers began to be used in agriculture and enterprises for their production were established. The rapid development of the German paint industry was associated with the work of Adolf von Bayer (1835-1917) on indigo and other dyes, and the industrial synthesis of ammonia under high pressure with the work of Fritz Haber (1868-1934).
The birth of physical chemistry. By the end of the 19th century the first works appeared in which the physical properties of various substances (boiling and melting points, solubility, molecular weight) were systematically studied. Such studies were initiated by Gay-Lussac and van't Hoff, who showed that the solubility of salts depends on temperature and pressure. In 1867, Norwegian chemists Peter Waage (1833-1900) and Kato Maximilian Guldberg (1836-1902) formulated the law of mass action, according to which the reaction rate depends on the concentrations of the reactants. The mathematical apparatus they used made it possible to find a very important quantity characterizing any chemical reaction - the rate constant.
Chemical thermodynamics. Meanwhile, chemists turned to the central question of physical chemistry - the effect of heat on chemical reactions. By the middle of the 19th century. physicists William Thomson (Lord Kelvin) (1824-1907), Ludwig Boltzmann (1844-1906) and James Maxwell (1831-1879) developed new views on the nature of heat. Rejecting Lavoisier's caloric theory, they presented heat as the result of motion. Their ideas were developed by Rudolf Clausius (1822-1888). He developed the kinetic theory, according to which such quantities as volume, pressure, temperature, viscosity and reaction rate can be considered based on the idea of ​​continuous movement of molecules and their collisions. Simultaneously with Thomson (1850), Clasius gave the first formulation of the second law of thermodynamics, introduced the concepts of entropy (1865), an ideal gas, and the free path of molecules. The thermodynamic approach to chemical reactions was applied in his works by August Friedrich Gorstmann (1842-1929), who, based on the ideas of Clausius, tried to explain the dissociation of salts in solution. In 1874-1878 the American chemist Josiah Willard Gibbs (1839-1903) undertook a systematic study of the thermodynamics of chemical reactions. He introduced the concept of free energy and chemical potential, explained the essence of the law of mass action, applied thermodynamic principles in studying the equilibrium between different phases at different temperatures, pressures and concentrations (the phase rule). Gibbs' work laid the foundation for modern chemical thermodynamics. The Swedish chemist Svante August Arrhenius (1859-1927) created the theory of ionic dissociation, which explains many electrochemical phenomena, and introduced the concept of activation energy. He also developed an electrochemical method for measuring the molecular weight of solutes. A prominent scientist, thanks to whom physical chemistry was recognized as an independent field of knowledge, was the German chemist Wilhelm Ostwald (1853-1932), who applied Gibbs' concepts in the study of catalysis. In 1886 he wrote the first textbook on physical chemistry, and in 1887 he founded (together with van't Hoff) the journal Physical Chemistry (Zeitschrift fr physikalische Chemie).
THE TWENTIETH CENTURY
New structural theory. With the development of physical theories about the structure of atoms and molecules, such old concepts as chemical affinity and transmutation were rethought. New ideas about the structure of matter arose.
Model of the atom. In 1896, Antoine Henri Becquerel (1852-1908) discovered the phenomenon of radioactivity, discovering the spontaneous emission of subatomic particles by uranium salts, and two years later, the spouses Pierre Curie (1859-1906) and Marie Sklodowska-Curie (1867-1934) isolated two radioactive elements: polonium and radium. In subsequent years, it was found that radioactive substances emit three types of radiation: a-particles, b-particles and g-rays. Together with the discovery of Frederick Soddy (1877-1956), which showed that during radioactive decay, some substances are transformed into others, all this gave a new meaning to what the ancients called transmutation. In 1897, Joseph John Thomson (1856-1940) discovered the electron, the charge of which was measured with high accuracy in 1909 by Robert Milliken (1868-1953). In 1911, Ernst Rutherford (1871-1937), based on Thomson's electronic concept, proposed a model of the atom: a positively charged nucleus is located in the center of the atom, and negatively charged electrons revolve around it. In 1913, Niels Bohr (1885-1962), using the principles of quantum mechanics, showed that electrons can be located not in any, but in strictly defined orbits. The Rutherford-Bohr planetary quantum model of the atom forced scientists to take a new approach to explaining the structure and properties of chemical compounds. The German physicist Walter Kossel (1888-1956) suggested that the chemical properties of an atom are determined by the number of electrons in its outer shell, and the formation of chemical bonds is determined mainly by the forces of electrostatic interaction. American scientists Gilbert Newton Lewis (1875-1946) and Irving Langmuir (1881-1957) formulated the electronic theory of chemical bonding. In accordance with these ideas, the molecules of inorganic salts are stabilized by electrostatic interactions between their constituent ions, which are formed during the transition of electrons from one element to another (ionic bond), and the molecules of organic compounds are stabilized due to the socialization of electrons (covalent bond). These ideas underlie modern ideas about the chemical bond.
New research methods. All new ideas about the structure of matter could be formed only as a result of the development in the 20th century. experimental technique and the emergence of new research methods. The discovery in 1895 by Wilhelm Conrad Roentgen (1845-1923) of X-rays served as the basis for the subsequent creation of the X-ray crystallography method, which makes it possible to determine the structure of molecules from the X-ray diffraction pattern on crystals. With the help of this method, the structure of complex organic compounds - insulin, deoxyribonucleic acid (DNA), hemoglobin, etc. was deciphered. With the creation of the atomic theory, new powerful spectroscopic methods appeared that provide information about the structure of atoms and molecules. Various biological processes, as well as the mechanism of chemical reactions, are studied using radioisotope labels; Radiation methods are also widely used in medicine.
Biochemistry. This scientific discipline, which deals with the study of the chemical properties of biological substances, was at first one of the branches of organic chemistry. It emerged as an independent region in the last decade of the 19th century. as a result of research on the chemical properties of substances of plant and animal origin. One of the first biochemists was the German scientist Emil Fischer (1852-1919). He synthesized substances such as caffeine, phenobarbital, glucose, many hydrocarbons, made a great contribution to the science of enzymes - protein catalysts, first isolated in 1878. The creation of new analytical methods contributed to the formation of biochemistry as a science. In 1923, the Swedish chemist Theodor Svedberg (1884-1971) designed an ultracentrifuge and developed a sedimentation method for determining the molecular weight of macromolecules, mainly proteins. Svedberg's assistant Arne Tiselius (1902-1971) in the same year created the method of electrophoresis, a more advanced method for separating giant molecules, based on the difference in the speed of migration of charged molecules in an electric field. At the beginning of the 20th century Russian chemist Mikhail Semenovich Tsvet (1872-1919) described a method for separating plant pigments by passing their mixture through a tube filled with an adsorbent. The method was called chromatography. In 1944, the English chemists Archer Martin (b. 1910) and Richard Sing (b. 1914) proposed a new version of the method: they replaced the adsorbent tube with filter paper. This is how paper chromatography appeared - one of the most common analytical methods in chemistry, biology and medicine, with the help of which in the late 1940s and early 1950s it was possible to analyze mixtures of amino acids resulting from the breakdown of various proteins and determine the composition of proteins. As a result of painstaking research, the order of amino acids in the insulin molecule was established (Frederick Sanger, 1953), and by 1964 this protein had been synthesized. Now many hormones, medicines, vitamins are obtained by biochemical synthesis methods.

Chemistry, as one of the sciences that study natural phenomena, originated in ancient Egypt before our era, one of the most technically advanced countries in those days. People received the first information about chemical transformations by doing various crafts, when they dyed fabrics, smelted metal, and made glass. Then certain techniques and recipes appeared, but chemistry was not yet a science. Even then, mankind needed chemistry mainly in order to obtain from nature all the materials necessary for human life - metals, ceramics, lime, cement, glass, dyes, medicines, precious metals, etc. Since ancient times, the main task of chemistry has been to obtain substances with the necessary properties.

In ancient Egypt, chemistry was considered a divine science and its secrets were carefully guarded by the priests. Despite this, some information leaked out of the country and reached Europe through Byzantium.

In the VIII century, in the European countries conquered by the Arabs, this science spread under the name "alchemy". It should be noted that in the history of the development of chemistry as a science, alchemy characterizes an entire era. The main task of the alchemists was to find the "philosopher's stone", supposedly turning any metal into gold. Despite the extensive knowledge gained as a result of experiments, the theoretical views of alchemists lagged behind by several centuries. But since they carried out various experiments, they managed to make several important practical inventions. Furnaces, retorts, flasks, apparatus for the distillation of liquids began to be used. Alchemists prepared the most important acids, salts and oxides, described the methods of decomposition of ores and minerals. As a theory, alchemists used the teachings of Aristotle (384-322 BC) about the four principles of nature (cold, heat, dryness and humidity) and the four elements (earth, fire, air and water), subsequently adding solubility to them (salt ), combustibility (sulphur) and metallicity (mercury).

At the beginning of the 16th century, a new era begins in alchemy. Its origin and development is connected with the teachings of Paracelsus (1493-1541) and Agricola (1494-1555). Paracelsus argued that the main task of chemistry is the manufacture of medicines, not gold and silver. Paracelsus had great success by suggesting that certain diseases be treated using simple inorganic compounds instead of organic extracts. This prompted many doctors to join his school and become interested in chemistry, which served as a powerful impetus for its development. Agricola also studied mining and metallurgy. His work "On Metals" was a textbook on mining for more than 200 years.

In the 17th century, the theory of alchemy no longer met the requirements of practice. In 1661, Boyle spoke out against the ideas prevailing in chemistry and subjected the theory of alchemists to the most severe criticism. He first identified the central object of chemistry research: he tried to define a chemical element. Boyle believed that an element is the limit of the decomposition of a substance into its component parts. Decomposing natural substances into their constituents, the researchers made many important observations, discovered new elements and compounds. The chemist began to study what consists of what.

In 1700, Stahl developed the phlogiston theory, according to which all bodies capable of burning and oxidizing contain the substance phlogiston. During combustion or oxidation, phlogiston leaves the body, which is the essence of these processes. During the almost century-old domination of the phlogiston theory, many gases were discovered, various metals, oxides, and salts were studied. However, the inconsistency of this theory hindered the further development of chemistry.

In 1772-1777, Lavoisier, as a result of his experiments, proved that the combustion process is a reaction of the combination of oxygen in the air and a burning substance. Thus, the phlogiston theory was refuted.

In the 18th century, chemistry began to develop as an exact science. At the beginning of the 19th century Englishman J. Dalton introduced the concept of atomic weight. Each chemical element received its most important characteristic. Atomic-molecular theory became the basis of theoretical chemistry. Thanks to this teaching, D. I. Mendeleev discovered the periodic law, named after him, and compiled the periodic table of elements. In the 19th century two main branches of chemistry were clearly defined: organic and inorganic. At the end of the century, physical chemistry took shape as an independent branch. The results of chemical research have been increasingly used in practice, and this has led to the development of chemical technology.