It has the shape of a ball, but imagined it as a disk and even a floating rectangle, fire, air, earth and water considered four basic elements of the universe. Who stopped calling water an element? Who deprived her of this high rank? ? A number of brave chemists, working independently, almost simultaneously made this discovery.
The discoverers of oxygen and hydrogen
Ever since the chemists pushed the alchemists and warlocks out of the retorts, the family of elements has grown at once. If a hundred years ago it numbered only 60 members, now, counting artificially obtained elements, there are a hundred of them. We will find their names, chemical sign, atomic weight and serial number in any chemical table. Only the names of the "ancestors" disappeared from it. The discoverers of oxygen and hydrogen are considered:- French chemist Antoine Laurent Lavoisier. He was the manager of a saltpeter and powder factory, and later, after the victory of the French bourgeois revolution, the commissioner of the national treasury, one of the most influential people in France.
- English chemist Henry Cavendish, originally from an old ducal family, who donated a large share of his fortune to science.
- Compatriot Cavendish, Joseph Priestley. He was a priest. As an ardent supporter of the French Revolution, Priestley was expelled from England and fled to America.
- Famous Swedish chemist Carl Wilhelm Scheele, pharmacist.
Oxygen - in water and air
Lavoisier, Priestley and Scheele made a series of experiments. First they discovered oxygen in water and air. Abbreviated in chemistry, it is denoted by the letter "O". When we saidThere is no life without waterthis has not yet been said to whom, in fact, the water owes its life-giving power. Now we can answer this question. The life-giving power of water is in oxygen. Oxygen is the most important element of the air envelope surrounding the Earth. Without oxygen, life goes out, like the flame of a candle placed under a glass jar. Even the largest fire subsides if burning objects are thrown with sand, cutting off oxygen access to them.
Now do you understand why the fire in the stove burns so badly if the view is closed? The same combustion process occurs in our body during metabolism. The steam engine works by using the thermal energy of burning coal. In the same way, our body uses the energy of those nutrients that we consume. The air that we breathe is necessary for the "stove" - our body - to burn well, because our body must have a certain temperature. When we exhale, we release water in the form of vapor and combustion products. 
Lavoisier studied these processes and found that combustion is the rapid combination of various substances with oxygen in the air. This creates warmth. But Lavoisier was not satisfied with the fact that discovered oxygen. He wanted to know what substances oxygen combines with. Discovery of hydrogen
Almost simultaneously with Cavendish, who also decomposed water into its component parts, Lavoisier discovered hydrogen. This element is called "Hydrogenium", which means: Hydrogen is denoted by the letter "H". Let's examine again whether hydrogen is really in composition of water. Fill a beaker with ice and heat it over the flame of an alcohol lamp. (Alcohol, like any alcohol, is rich in hydrogen.) And what will we see? The outer side of the test tube will be covered with dew. Or hold a clean knife over a candle flame. The knife will also be covered with drops of water. Where does water come from? Water comes from fire. So fire is the source of water! This is not a new discovery, and yet it is amazing. Chemists would say this: when hydrogen is burned, in other words, Hydrogen combines with oxygen to form water vapor. That is why the test tube and the knife are covered with drops of water. That's how it happened discovery of the composition of water. So, hydrogen, which is 16 times lighter than oxygen and 14 times lighter than air, burns! At the same time, it generates a large amount of heat. In the past, balloons were filled with hydrogen. It was very dangerous. Now helium is used instead of hydrogen. You can also answer the second question:Why doesn't water burn?This question seems so simple that we didn't even ask it at first. Most will say:
The water is wet, so it doesn't burn.Wrong. Gasoline is "wet" too, but don't try to see if it's on fire! Water does not burn because it itself was formed as a result of combustion. This, one might say, is the "liquid ash" of hydrogen. That is why water puts out fire as well as sand.
The purpose of today's publication is to provide the unprepared reader with comprehensive information about what is hydrogen, what are its physical and chemical properties, scope, significance and methods of obtaining.
Hydrogen is present in the vast majority of organic substances and cells, in which it accounts for almost two-thirds of the atoms.
Photo 1. Hydrogen is considered one of the most common elements in nature
In Mendeleev's periodic system of elements, hydrogen occupies the honorable first position with an atomic weight equal to one.
The name "hydrogen" (in the Latin version - Hydrogenium) originates from two ancient Greek words: ὕδωρ - “” and γεννάω - “I give birth” (literally - “giving birth) and was first proposed in 1824 by the Russian chemist Mikhail Solovyov.
Hydrogen is one of the water-forming (along with oxygen) elements (the chemical formula of water is H 2 O).
According to its physical properties, hydrogen is characterized as a colorless gas (lighter than air). When mixed with oxygen or air, it is extremely flammable.
Able to dissolve in some metals (titanium, iron, platinum, palladium, nickel) and in ethanol, but very poorly soluble in silver.
The hydrogen molecule consists of two atoms and is designated H 2 . Hydrogen has several isotopes: protium (H), deuterium (D), and tritium (T).
History of the discovery of hydrogen
Back in the first half of the 16th century, while conducting alchemical experiments, mixing metals with acids, Paracelsus noticed a hitherto unknown combustible gas, which he could not separate from the air.
After almost a century and a half - at the end of the 17th century - the French scientist Lemery managed to separate hydrogen (not yet knowing that it was hydrogen) from air and prove its combustibility.
Photo 2. Henry Cavendish - the discoverer of hydrogen
Chemical experiments in the middle of the 18th century allowed Mikhail Lomonosov to reveal the process of the release of a certain gas as a result of some chemical reactions, which, however, is not phlogiston.
A real breakthrough in the study of combustible gas was made by an English chemist Henry Cavendish, to whom the discovery of hydrogen is attributed (1766).
Cavendish called this gas "combustible air". He also carried out the combustion reaction of this substance, which resulted in water.
In 1783, French chemists led by Antoine Lavoisier carried out the synthesis of water, and subsequently - the decomposition of water with the release of "combustible air".
These studies finally proved the presence of hydrogen in the composition of water. It was Lavoisier who suggested calling the new gas Hydrogenium (1801).
Useful properties of hydrogen
Hydrogen is fourteen and a half times lighter than air.
It is also distinguished by the highest thermal conductivity among other gases (whiter than seven times the thermal conductivity of air).
In the past, balloons and airships were filled with hydrogen. After a series of catastrophes in the mid-1930s, ending with airship explosions, designers had to look for a replacement for hydrogen.
Now, for such aircraft, helium is used, which is much more expensive than hydrogen, but not so explosive.
Photo 3. Hydrogen is used to make rocket fuel
In many countries, research is underway to create economical engines for cars and trucks based on hydrogen.
Hydrogen-powered vehicles are much more environmentally friendly than their petrol and diesel counterparts.
Under normal conditions (room temperature and natural pressure), hydrogen is reluctant to react.
When a mixture of hydrogen and oxygen is heated to 600 °C, a reaction begins, culminating in the formation of water molecules.
The same reaction can be provoked with an electric spark.
Reactions with the participation of hydrogen are completed only when the components involved in the reaction are completely consumed.
The temperature of burning hydrogen reaches 2500-2800 °C.
Hydrogen is used to purify various types of fuel based on oil and petroleum products.
In living nature, there is nothing to replace hydrogen, since it is present in any organic matter (including oil) and in all protein compounds.
Without the participation of hydrogen would be impossible.
Aggregate states of hydrogen
Hydrogen can exist in three main states of aggregation:
- gaseous;
- liquid;
- hard.
The usual state of hydrogen is a gas. By lowering its temperature to -252.8 °C, hydrogen turns into a liquid, and after a temperature threshold of -262 °C, hydrogen becomes solid.
Photo 4. For several decades, expensive helium has been used to fill balloons instead of cheap hydrogen
Scientists suggest that hydrogen is able to be in an additional (fourth) state of aggregation - metallic.
To do this, you just need to create a pressure of two and a half million atmospheres.
So far, alas, this is just a scientific hypothesis, since no one has yet been able to obtain “metallic hydrogen”.
Liquid hydrogen - due to its temperature - if it comes into contact with human skin, it can cause severe frostbite.
Hydrogen in the periodic table
The distribution of chemical elements in the periodic table of Mendeleev is based on their atomic weight, calculated relative to the atomic weight of hydrogen.
Photo 5. In the periodic table, hydrogen is assigned a cell with serial number 1
For many years, no one could either refute or confirm this approach.
With the appearance at the beginning of the 20th century and, in particular, the emergence of the famous postulates of Niels Bohr, explaining the structure of the atom from the standpoint of quantum mechanics, it was possible to prove the validity of Mendeleev's hypothesis.
The opposite is also true: it was precisely the correspondence of Niels Bohr's postulates to the periodic law underlying the periodic table that became the most compelling argument in favor of recognizing their truth.
The participation of hydrogen in a thermonuclear reaction
Hydrogen isotopes deuterium and tritium are sources of incredibly powerful energy released during a thermonuclear reaction.
Photo 6. Thermonuclear explosion without hydrogen would be impossible
Such a reaction is possible at a temperature not lower than 1060 ° C and proceed very quickly - within a few seconds.
On the Sun, thermonuclear reactions proceed slowly.
The task of scientists is to understand why this happens in order to use the knowledge gained to create new - almost inexhaustible - sources of energy.
What is hydrogen (video):
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The history of the discovery of hydrogen occupies an important milestone in the development of science. According to modern scientific concepts, this gas is one of the most important substances for the existence of stars, and, therefore, the main source of energy.
A Brief History of the Discovery of Hydrogen
The element was discovered by a British scientist in 1766. The origin of the name goes back to the Greek words "hydro" and "genes", which means "water" and "generator".
As early as 1671, Robert Boyle (1627-1691, English chemist and physicist) published "New Experiments Concerning the Relationship Between Flame and Air" in which he described the reaction between iron filings and dilute acids. During the experiments, the scientist noticed that the reaction of these substances leads to the evolution of hydrogen gas (“combustible solution of Mars”).
However, it was not until 1766 that gas was approved as the main element by Henry Cavendish (1731-1810, an English chemist and physicist who also discovered nitrogen), who used mercury for synthesis. The scientist described it as "flammable air of metals". Cavendish accurately described the properties of hydrogen, but erroneously believed that the gas came from a metal and not from an acid. The modern name for the chemical element was given by the French naturalist A. L. Lavoisier.
The history of the discovery of hydrogen (H) does not end there. In 1931, chemistry professor Harold Urey, who worked in Chicago (USA), discovered deuterium gas. It is the heavy isotope of hydrogen and is written as 2 H and D.
The building blocks of the universe
For a long time people could not understand the properties of matter. Although the ancient Greeks assumed that the "ether" (surrounding space) consists of certain elements, there was no clear justification and, all the more, solid evidence for this fact.
In the autumn of 1803, the Englishman was able to explain the results of some of his research by assuming that matter was composed of atoms. The researcher also found that all samples of any given compound are composed of the same combination of these atoms. Dalton also noted that in a number of compounds, the ratios of the masses of the second element, which are combined with a given weight of the first element, can be reduced to small integers ("Law of Multiple Proportions"). Thus, the scientist has a certain relation to the history of the discovery of hydrogen.
The presentation of Dalton's "Theory of Atoms" took place in the 3rd volume of the scientific edition "Systems of Chemistry", published by Thomas Thomson in 1807. The material also appeared in an article on strontium oxalates published in Philosophical Transactions. The following year, Dalton published these ideas on his own, making a more extensive analysis in The New System of Chemical Philosophy. By the way, in it the scientist suggested using a circle with a dot in the center as a symbol of hydrogen.
First fuel cell
The history of the discovery of hydrogen is rich in interesting events. In 1839, British scientist Sir William Robert Grove conducted experiments on electrolysis. He used electricity to split water into hydrogen and oxygen. Later, the researcher wondered if it was possible to do the opposite - to generate electricity from the reaction of oxygen with hydrogen? Grove sealed the platinum records in separate sealed containers, one containing hydrogen and the other oxygen. When the containers were immersed in dilute sulfuric acid, a current flowed between the two electrodes, forming water in the gas cylinders. Then the scientist connected several similar devices in a series circuit to increase the voltage created in the gas battery.
Since then, great hopes have been placed on hydrogen in terms of obtaining compact, environmentally friendly energy sources. However, the issue of 100% security and high efficiency of end devices for mass consumption has not yet been resolved. By the way, the term "fuel cell" was first used by chemists Ludwig Mond and Charles Langer, who continued the research of W. R. Grove.
Autonomous energy sources
In 1932, Francis Thomas Bacon, an engineer at the University of Cambridge in the UK, continued to work on the Grove, Mond and Langer designs. He replaced the platinum electrodes with a less expensive nickel mesh, and instead of an electrolyte with sulfuric acid, he used alkaline potassium hydroxide (less corrosive to the electrodes). This was essentially the creation of the first alkaline fuel cell, called the Bacon cell. It took another 27 years for the British to demonstrate a plant capable of producing 5 kW of energy, enough to power a welding machine. Around the same time, the first fuel cell vehicle was demonstrated.
Fuel cells were later used by NASA in the 1960s for the Apollo lunar program. Bacon's cells were (and are) on hundreds of spacecraft. Also "large batteries" are used on submarines.
Useful but dangerous
The history of the discovery of hydrogen is associated not only with joyful moments. The tragedy of the giant airship Hindenburg testifies to how unsafe this element is. In the 1930s, Germany built a series of aircraft - zeppelins. Hydrogen was used as the gas. Being lighter than the nitrogen-oxygen mixture that makes up the bulk of the atmosphere, it made it possible to transport large volumes of cargo.
In 1936, German designers presented to the world the largest airship at that time, the Hindenburg. The 245-meter giant contained 200,000 m3 of gas. Its carrying capacity is amazing: the device was able to lift up to 100 tons of cargo into the sky. The aircraft was used for transatlantic transport between Germany and the United States. The passenger gondola accommodated 50 people with luggage. 05/06/1937 upon arrival in New York, a hydrogen leak occurred. The flammable gas ignited, causing an explosion that killed 36 people. Since then, the safer helium has been used instead of hydrogen in aircraft.
Conclusion
Hydrogen is one of the most important elements in the universe. Although its properties are well studied, it does not cease to interest scientists, engineers, and designers. This element is the subject of thousands of scientific papers, diplomas and abstracts. The history of the discovery of hydrogen is the history of science itself, a system of knowledge that has replaced ignorance and religious dogmas.
In the periodic system, hydrogen is located in two groups of elements that are absolutely opposite in their properties. This feature makes it completely unique. Hydrogen is not just an element or substance, but also a component of many complex compounds, an organogenic and biogenic element. Therefore, we consider its properties and characteristics in more detail.
The release of combustible gas during the interaction of metals and acids was observed as early as the 16th century, that is, during the formation of chemistry as a science. The famous English scientist Henry Cavendish studied the substance starting in 1766 and gave it the name "combustible air". When burned, this gas produced water. Unfortunately, the scientist's adherence to the theory of phlogiston (hypothetical "hyperfine matter") prevented him from coming to the right conclusions.
The French chemist and naturalist A. Lavoisier, together with the engineer J. Meunier and with the help of special gasometers, in 1783 carried out the synthesis of water, and then its analysis by decomposing water vapor with red-hot iron. Thus, scientists were able to come to the right conclusions. They found that "combustible air" is not only part of the water, but can also be obtained from it.
In 1787, Lavoisier suggested that the gas under study is a simple substance and, accordingly, is one of the primary chemical elements. He called it hydrogene (from the Greek words hydor - water + gennao - I give birth), that is, "giving birth to water."
The Russian name "hydrogen" was proposed in 1824 by the chemist M. Solovyov. The determination of the composition of water marked the end of the "phlogiston theory". At the turn of the 18th and 19th centuries, it was found that the hydrogen atom is very light (compared to the atoms of other elements) and its mass was taken as the main unit for comparing atomic masses, obtaining a value equal to 1.
Physical Properties
Hydrogen is the lightest of all substances known to science (it is 14.4 times lighter than air), its density is 0.0899 g/l (1 atm, 0 °C). This material melts (solidifies) and boils (liquefies), respectively, at -259.1 ° C and -252.8 ° C (only helium has lower boiling and melting t °).
The critical temperature of hydrogen is extremely low (-240 °C). For this reason, its liquefaction is a rather complicated and costly process. The critical pressure of a substance is 12.8 kgf / cm², and the critical density is 0.0312 g / cm³. Among all gases, hydrogen has the highest thermal conductivity: at 1 atm and 0 ° C, it is 0.174 W / (mxK).
The specific heat capacity of a substance under the same conditions is 14.208 kJ / (kgxK) or 3.394 cal / (gh ° C). This element is slightly soluble in water (about 0.0182 ml / g at 1 atm and 20 ° C), but well - in most metals (Ni, Pt, Pa and others), especially in palladium (about 850 volumes per volume of Pd ).
The latter property is associated with its ability to diffuse, while diffusion through a carbon alloy (for example, steel) may be accompanied by the destruction of the alloy due to the interaction of hydrogen with carbon (this process is called decarbonization). In the liquid state, the substance is very light (density - 0.0708 g / cm³ at t ° \u003d -253 ° C) and fluid (viscosity - 13.8 centigrade under the same conditions).
In many compounds, this element exhibits a +1 valency (oxidation state), similar to sodium and other alkali metals. It is usually considered as an analogue of these metals. Accordingly, he heads the I group of the Mendeleev system. In metal hydrides, the hydrogen ion exhibits a negative charge (the oxidation state is -1), that is, Na + H- has a structure similar to Na + Cl- chloride. In accordance with this and some other facts (the closeness of the physical properties of the element "H" and halogens, the ability to replace it with halogens in organic compounds), Hydrogene is assigned to group VII of the Mendeleev system.
Under normal conditions, molecular hydrogen has low activity, directly combining only with the most active of non-metals (with fluorine and chlorine, with the latter - in the light). In turn, when heated, it interacts with many chemical elements.
Atomic hydrogen has an increased chemical activity (compared to molecular hydrogen). With oxygen, it forms water according to the formula:
Н₂ + ½О₂ = Н₂О,
releasing 285.937 kJ/mol of heat or 68.3174 kcal/mol (25°C, 1 atm). Under normal temperature conditions, the reaction proceeds rather slowly, and at t ° >= 550 ° С, it is uncontrolled. The explosive limits of a mixture of hydrogen + oxygen by volume are 4–94% H₂, and mixtures of hydrogen + air are 4–74% H₂ (a mixture of two volumes of H₂ and one volume of O₂ is called explosive gas).
This element is used to reduce most metals, since it takes oxygen from oxides:
Fe₃O₄ + 4H₂ = 3Fe + 4Н₂О,
CuO + H₂ = Cu + H₂O etc.
With different halogens, hydrogen forms hydrogen halides, for example:
H₂ + Cl₂ = 2HCl.
However, when reacting with fluorine, hydrogen explodes (this also happens in the dark, at -252 ° C), reacts with bromine and chlorine only when heated or illuminated, and with iodine only when heated. When interacting with nitrogen, ammonia is formed, but only on a catalyst, at elevated pressures and temperatures:
ZN₂ + N₂ = 2NH₃.
When heated, hydrogen actively reacts with sulfur:
H₂ + S = H₂S (hydrogen sulfide),
and much more difficult - with tellurium or selenium. Hydrogen reacts with pure carbon without a catalyst, but at high temperatures:
2H₂ + C (amorphous) = CH₄ (methane).
This substance directly reacts with some of the metals (alkali, alkaline earth and others), forming hydrides, for example:
Н₂ + 2Li = 2LiH.
Of no small practical importance are the interactions of hydrogen and carbon monoxide (II). In this case, depending on the pressure, temperature and catalyst, various organic compounds are formed: HCHO, CH₃OH, etc. Unsaturated hydrocarbons turn into saturated ones during the reaction, for example:
С n Н₂ n + Н₂ = С n Н₂ n ₊₂.
Hydrogen and its compounds play an exceptional role in chemistry. It determines the acidic properties of the so-called. protic acids tend to form hydrogen bonds with different elements, which have a significant effect on the properties of many inorganic and organic compounds.
Getting hydrogen
The main types of raw materials for the industrial production of this element are refinery gases, natural combustible and coke oven gases. It is also obtained from water through electrolysis (in places with affordable electricity). One of the most important methods for producing material from natural gas is the catalytic interaction of hydrocarbons, mainly methane, with water vapor (the so-called conversion). For example:
CH₄ + H₂O = CO + ZH₂.
Incomplete oxidation of hydrocarbons with oxygen:
CH₄ + ½O₂ \u003d CO + 2H₂.
Synthesized carbon monoxide (II) undergoes conversion:
CO + H₂O = CO₂ + H₂.
Hydrogen produced from natural gas is the cheapest.
For electrolysis of water, direct current is used, which is passed through a solution of NaOH or KOH (acids are not used to avoid corrosion of the equipment). Under laboratory conditions, the material is obtained by electrolysis of water or as a result of the reaction between hydrochloric acid and zinc. However, more often used ready-made factory material in cylinders.
From refinery gases and coke oven gas, this element is isolated by removing all other components of the gas mixture, since they are more easily liquefied during deep cooling.
This material began to be obtained industrially at the end of the 18th century. Then it was used to fill balloons. At the moment, hydrogen is widely used in industry, mainly in the chemical industry, for the production of ammonia.
Mass consumers of the substance are manufacturers of methyl and other alcohols, synthetic gasoline and many other products. They are obtained by synthesis from carbon monoxide (II) and hydrogen. Hydrogene is used for the hydrogenation of heavy and solid liquid fuels, fats, etc., for the synthesis of HCl, hydrotreating of petroleum products, as well as in cutting / welding of metals. The most important elements for nuclear energy are its isotopes - tritium and deuterium.
The biological role of hydrogen
About 10% of the mass of living organisms (on average) falls on this element. It is part of water and the most important groups of natural compounds, including proteins, nucleic acids, lipids, carbohydrates. What does it serve?
This material plays a decisive role: in maintaining the spatial structure of proteins (quaternary), in implementing the principle of complementarity of nucleic acids (i.e., in the implementation and storage of genetic information), in general, in “recognition” at the molecular level.
The hydrogen ion H+ takes part in important dynamic reactions/processes in the body. Including: in biological oxidation, which provides living cells with energy, in biosynthesis reactions, in photosynthesis in plants, in bacterial photosynthesis and nitrogen fixation, in maintaining acid-base balance and homeostasis, in membrane transport processes. Along with carbon and oxygen, it forms the functional and structural basis of the phenomena of life.
After the work of J. Black, many chemists in various laboratories in England, Sweden, France, and Germany began to study gases. G. Cavendish achieved great success. All the experimental work of this scrupulous scientist was based on a quantitative research method. He widely used the weighing of substances and the measurement of gas volumes, guided by the law of conservation of mass. In the first work of G. Cavendnsh on the chemistry of gases (1766), methods of obtaining and properties are described.
"Combustible air" was known before (R. Boyle, N. Lemery). In 1745, M. V. Lomonosov, for example, noted that “when a base metal is dissolved, especially in acidic alcohols, combustible vapor escapes from the bottle opening, which is nothing more than phlogiston.” This is noteworthy in two respects: firstly, many years before the Cavendish, M. V. Lomonosov came to the conclusion that “combustible air” (i.e., hydrogen) is phlogiston; secondly, from the above quotation it follows that M. V. Lomonosov accepted the doctrine of phlogiston.
But no one before G. Cavendish tried to isolate "combustible air" and study its properties. In the chemical treatise Three Works Containing Experiments with Artificial Types of Air (1766), he showed that there are gases that differ from air, namely, on the one hand, "forest or bound air", which, as established by G. Cavendish turned out to be 1.57 times heavier than ordinary air, on the other hand, “combustible air” is hydrogen. G. Cavendish received it by the action of dilute acids and acids on various metals. The fact that under the action on (zinc, iron) the same gas (hydrogen) was released finally convinced G. Cavendish that all metals contain phlogiston, which is released during the transformation of metals into "earths". The English scientist took hydrogen for pure phlogiston, since the gas burns without leaving a residue, and metal oxides treated with this gas are reduced to the corresponding metals when heated.
Henry Cavendish G. Cavendish, as a supporter of the theory of phlogiston, believed that it was not displaced by the metal from the acid, but was released as a result of the decomposition of the "complex" metal. He represented the reaction of obtaining "combustible air" from metals as follows:
What methods and instruments the "father of the chemistry of gaseous substances" used can be seen from the following. Leaving Leeds, J. Priestley, at the request of one of his acquaintances, left him a clay trough, which he used as a pneumatic bath in his experiments on the composition of air and which, J. Priestley ironically remarks, “was no different from the troughs in which laundresses wash clothes ". In 1772, J. Priestley replaced water with mercury in a pneumatic bath, which allowed him for the first time to obtain in pure form and study water-soluble gases: “hydrochloric acid air” () and “volatile alkaline air” - a colorless gas with a suffocating pungent odor. This was the one he got by heating ammonium chloride:
2NH 4 Cl + CaO \u003d 2NH 3 + CaCl 2 + H 2
“The gold placer discovered by Priestley was ... a mercury bath,” W. Ostwald wrote. “One step ahead on the technical side of things—water changes—is the key to most of Priestley’s discoveries.” J. Priestley observed that if an electric spark is passed through ammonia, then its volume increases sharply. In 1785, K.-L. Berthollet established that this was due to the decomposition of ammonia into nitrogen and hydrogen. J. Priestley observed that the interaction of two strongly smelling gases (HCl and NH 3) produces an odorless white powder (NH 4 Cl). In 1775, J. Priestley received, and c. 1796 - which he mistook for pure phlogiston.
