Oxygen gas. Properties, production, use and price of oxygen. Oxygen: chemical properties of the element

The lump in the throat is oxygen. It was found that in a state of stress, the glottis expands. It is located in the middle of the larynx, limited by 2 muscle folds.

It is they who put pressure on nearby tissues, creating a sensation of a lump in the throat. The expansion of the gap is a consequence of increased oxygen consumption. It helps to cope with stress. So, the notorious lump in the throat can be called oxygen.

The 8th element of the table is familiar in the form . But sometimes liquid oxygen. Element magnetized in this state. However, we will talk about the properties of oxygen and the advantages that can be extracted from them in the main part.

Properties of oxygen

Due magnetic properties oxygen is moved with the help of powerful. If we talk about the element in habitual state, he himself is able to move, in particular, electrons.

Actually, the respiratory system is built on the redox potential of a substance. Oxygen in it is the final acceptor, that is, the receiving agent.

Enzymes act as donors. Substances oxidized with oxygen are released into external environment. It's carbon dioxide. It produces from 5 to 18 liters per hour.

Another 50 grams of water comes out. So drinking plenty of water is a reasonable recommendation from doctors. Plus, the by-products of breathing are about 400 substances. Among them is acetone. Its release is enhanced in a number of diseases, for example, diabetes.

The usual modification of oxygen, O 2, is involved in the process of respiration. This is a diatomic molecule. It has 2 unpaired electrons. Both are in antibonding orbitals.

They have a greater energy charge than binders. Therefore, the oxygen molecule easily breaks up into atoms. The dissociation energy reaches almost 500 kilojoules per mole.

IN vivo oxygen - gas with almost inert molecules. They have a strong interatomic bond. Oxidation processes are barely noticeable. Catalysts are needed to speed up reactions. In the body they are enzymes. They provoke the formation of radicals, which excite the chain process.

Temperature can be a catalyst for chemical reactions with oxygen. The 8th element reacts even to a slight heating. Heat gives reactions with hydrogen, methane and other combustible gases.

Interactions proceed with explosions. No wonder that one of the first airships in the history of mankind exploded. It was filled with hydrogen. The aircraft was called the Hindenburg and crashed in 1937.

Heating allows oxygen to create bonds with all elements of the periodic table, except for inert gases, i.e. argon, neon and helium. By the way, helium has become a substitute for filling airships.

The gas does not enter into the reaction, only it is expensive. But, back to the hero of the article. Oxygen is a chemical element interacting with metals even at room temperature.

It is enough for contact with some complex connections. The latter include nitrogen oxides. But with simple nitrogen chemical element oxygen reacts only at 1200 degrees Celsius.

For the reactions of the hero of the article with non-metals, heating is required at least up to 60 degrees Celsius. This is sufficient, for example, for contact with phosphorus. The hero of the article interacts with gray already at 250 degrees. By the way, sulfur is included in oxygen subgroup elements. She is the main one in the 6th group of the periodic table.

Oxygen interacts with carbon at 700-800 degrees Celsius. This refers to the oxidation of graphite. This mineral is one of the crystalline forms of carbon.

By the way, oxidation is the role of oxygen in any reactions. Most of them proceed with the release of light and heat. Simply put, the interaction of substances leads to combustion.

The biological activity of oxygen is due to its solubility in water. At room temperature, 3 milliliters of the 8th substance dissociate in it. The calculation is based on 100 milliliters of water.

The element shows high performance in ethanol and acetone. They dissolve 22 grams of oxygen. The maximum dissociation is observed in liquids containing fluorine, for example, perfluorobutitetrahydrofuran. Almost 50 grams of the 8th element are dissolved per 100 milliliters of it.

Speaking of dissolved oxygen, let's mention its isotopes. Atmospheric ranked 160th number. Its in the air 99.7%. 0.3% are isotopes 170 and 180. Their molecules are heavier.

Contacting with them, the water hardly passes into a vapor state. Only the 160th modification of the 8th element rises into the air. Heavy isotopes remain in the seas and oceans.

Interestingly, in addition to the gaseous and liquid states, oxygen is solid. It, like the liquid version, is formed at sub-zero temperatures. For watery oxygen, -182 degrees are needed, and for stone, at least -223.

The latter temperature gives the cubic lattice of crystals. From -229 to -249 degrees Celsius, the crystal structure of oxygen is already hexagonal. Artificially obtained and other modifications. But, for them, in addition to low temperatures, increased pressure is required.

In the usual state oxygen belongs to the elements with 2 atoms, it is colorless and odorless. However, there is a 3-atomic version of the hero of the article. This is ozone.

It has a pronounced fresh aroma. It's pleasant, but toxic. The difference from ordinary oxygen is also a large mass of molecules. Atoms come together in lightning discharges.

Therefore, the smell of ozone is felt after showers. You can feel the aroma and high altitudes 10-30 kilometers. There, the formation of ozone provokes ultraviolet radiation. Oxygen atoms capture the radiation of the sun, combining into large molecules. This, in fact, saves humanity from radiation.

Oxygen production

Industrialists get the hero of the article out of thin air. It is cleaned from water vapor, carbon monoxide and dust. Then, the air is liquefied. After purification, only nitrogen and oxygen remain. The first one evaporates at -192 degrees.

The oxygen remains. But, Russian scientists have discovered a storehouse of the already liquefied element. It is located in the mantle of the Earth. It is also called the geosphere. There is a layer under the solid crust of the planet and above its core.

Install there oxygen element sign helped laser press. We worked with him at the DESY Synchrotron Center. It is located in Germany. The research was carried out jointly with German scientists. Together, they calculated that the oxygen content in the alleged layer of mania is 8-10 times greater than in the atmosphere.

Let us clarify the practice of calculating deep oxygen rivers. Physicists have worked with iron oxide. Squeezing and heating it, scientists received all new metal oxides, previously unknown.

When it came to temperatures of 1,000 degrees and pressures 670,000 times atmospheric, the compound Fe 25 O 32 was obtained. The conditions of the middle layers of the geosphere are described.

The oxide conversion reaction goes with a global release of oxygen. It should be assumed that this also happens inside the planet. Iron is a typical element for the mantle.

Combination of an element with oxygen also typical. The version that atmospheric gas has seeped out of the ground over millions of years and accumulated near its surface is not typical.

Roughly speaking, scientists questioned the dominant role of plants in the formation of oxygen. Greens can give only part of the gas. In this case, you need to be afraid not only of the destruction of the flora, but also of the cooling of the core of the planet.

A decrease in mantle temperature can block the formation of oxygen. Mass fraction it in the atmosphere will also decline, and at the same time, life on the planet.

The question of how to extract oxygen from mania is not worth it. It is impossible to drill the earth to a depth of more than 7,000-8,000 kilometers. It remains to wait until the hero of the article seeps to the surface himself and extracts him from the atmosphere.

Application of oxygen

The active use of oxygen in industry began with the invention of turboexpanders. They appeared in the middle of the last century. Devices liquefy the air and separate it. Actually, these are installations for mining oxygen.

What elements are formed the circle of "communication" of the hero of the article? First, they are metals. This is not about direct interaction, but about the melting of elements. Oxygen is added to the burners to burn the fuel as efficiently as possible.

As a result, metals soften faster, mixing into alloys. Without oxygen, for example, the convector method of steel production is indispensable. Ordinary air as an ignition is ineffective. Not without liquefied gas in cylinders and metal cutting.

Oxygen as a chemical element was discovered and farmers. In liquefied form, the substance enters cocktails for animals. They are actively gaining weight. The connection between oxygen and the mass of animals can be traced in the Carboniferous period of the Earth's development.

The era is marked by a hot climate, an abundance of plants, and, consequently, of the 8th gas. As a result, centipedes under 3 meters long crawled around the planet. Insect fossils have been found. The scheme still works today. Give the animal a constant supplement to the usual portion of oxygen, you will get an increase in biological mass.

Doctors stock up on oxygen in cylinders for stopping, that is, stopping asthma attacks. Gas is also needed when eliminating hypoxia. This is what is called oxygen starvation. The 8th element also helps with ailments of the gastrointestinal tract.

In this case, oxygen cocktails become medicine. In other cases, the substance is given to patients in rubberized pillows, or through special tubes and masks.

In the chemical industry, the hero of the article is an oxidizing agent. The reactions in which the 8th element can participate have already been mentioned. Characterization of oxygen positively considered, for example, in rocket science.

The hero of the article was chosen as a fuel oxidizer for ships. The combination of both modifications of the 8th element is recognized as the most powerful oxidizing mixture. That is, rocket fuel interacts with ordinary oxygen and ozone.

The price of oxygen

The hero of the article is sold in balloons. They provide element link. With oxygen you can buy cylinders in 5, 10, 20, 40, 50 liters. In general, the standard step between tare volumes is 5-10 liters. The price range for the 40-liter version, for example, is from 3,000 to 8,500 rubles.

Next to the high price tags, as a rule, there is an indication of the observed GOST. His number is "949-73". In advertisements with the budget cost of cylinders, GOST is rarely registered, which is alarming.

Transportation of oxygen in cylinders

Philosophically speaking, oxygen is priceless. The element is the basis of life. Oxygen transports iron throughout the human body. A bunch of elements is called hemoglobin. Its deficiency is anemia.

The disease has serious consequences. The first of these is a decrease in immunity. Interestingly, in some animals, blood oxygen is not carried by iron. In horseshoe crabs, for example, copper delivers the 8th element to the organs.

Oxygen atoms can form two types of molecules: O 2 - oxygen and O 3 - ozone.

The phenomenon of the existence of several simple substances formed by atoms of one chemical element is called alotropy. And simple substances formed by one element are called alotropic modifications.

Therefore, ozone and oxygen are allotropic modifications of the element Oxygen.

Chemical properties of oxygen and ozone

Interaction of oxygen with metals

Molecular oxygen is a fairly strong oxidizing agent. It oxidizes almost all metals (except gold and platinum). Many metals slowly oxidize in air, but in an atmosphere of pure oxygen they burn out very quickly, and an oxide is formed:

However, some metals during combustion do not form oxides, but peroxides (in such compounds, the oxidation state of oxygen is -1) or superoxide (the oxidation state of the oxygen atom is fractional). Examples of such metals are barium, sodium and potassium:

Interaction of oxygen with non-metals

Oxygen exhibits an oxidation state of -2 in compounds that are formed with all nonmetals except Fluorine, Helium, Neon, and Argon. When heated, oxygen molecules directly interact with all non-metals, except for halogens and inert gases. In an oxygen atmosphere, phosphorus ignites spontaneously and some other non-metals:

When oxygen interacts with fluorine, oxygen fluoride is formed, and not fluorine oxide, since the fluorine atom has a higher electronegativity than the oxygen atom. Oxygen fluoride is a pale yellow gas. It is used as a very strongan oxidizing agent; and a fluorescent agent. In this compound, the oxidation state of Oxygen is +2.

In excess of fluorine, dioxygen difluoride can be formed, in which the oxidation state of oxygen is +1. In structure, such a molecule is similar to the hydrogen peroxide molecule.

The use of oxygen and ozone. Meaning ozone layer

Oxygen is used by all aerobic living beings for respiration. During photosynthesis, plants release oxygen and take in carbon dioxide.

Molecular oxygen is used for the so-called intensification, that is, the acceleration of oxidative processes in the metallurgical industry. Oxygen is also used to produce a flame with a high temperature. When acetylene (C 2 H 2) burns in oxygen, the flame temperature reaches 3500 °C. In medicine, oxygen is used to facilitate the breathing of patients. It is also used in breathing apparatus for working people in difficult-to-breathe atmospheres. Liquid oxygen is used as an oxidizer for rocket fuel.

Ozone is used in laboratory practice as a very strong oxidizing agent. In industry, it is used to disinfect water, since it has a strong oxidizing effect, which destroys various microorganisms.

Peroxides, superoxides and ozonides alkali metals used for the regeneration of oxygen in spacecraft and submarines. Such an application is based on the reaction of these substances with carbon dioxide CO 2:

In nature, ozone is found in the high layers of the atmosphere at an altitude of about 20-25 km, in the so-called ozone layer, which protects the Earth from harsh solar radiation. A decrease in the concentration of ozone in the stratosphere by at least 1 can lead to serious consequences, such as an increase in the number of skin cancers in humans and animals, an increase in the number of diseases associated with suppression of the human immune system, growth retardation land plants, reduced growth rate of phytoplankton, etc.

Without ozone layer life on the planet would be impossible. Meanwhile, atmospheric pollution from various industrial emissions leads to the destruction of the ozone layer. by the most hazardous substances for ozone are freons (they are used as refrigerants in refrigerators, as well as fillers for deodorant cans) and rocket fuel waste.

The world community is very concerned about the formation of a hole in the ozone layer at the poles of our planet, in connection with which in 1987 the "Montreal Protocol on Substances that Deplete the Ozone Layer" was adopted, which limited the use of substances harmful to the ozone layer.

Physical properties of substances formed by the element Sulfur

Sulfur atoms, as well as oxygen atoms, can form various allotropic modifications ( S∞ ; S12; S8; S6; S2 and others). At room temperature, sulfur is in the formα -sulfur (or rhombic sulfur), which is yellow brittle crystals, odorless, insoluble in water. At temperatures above +96 °C there is a slow transitionα-sulfur to β -sulfur (or monoclinic sulfur), which is almost white plates. If molten sulfur is poured into water, supercooling of liquid sulfur occurs and yellow-brown rubber-like plastic sulfur is formed, which later turns into a-sulfur again. Sulfur boils at a temperature equal to +445 ° C, forming dark brown vapors.

All modifications of sulfur do not dissolve in water, but rather well dissolve in carbon disulfide(CS2) and some other non-polar solvents.

Sulfur application

The main product of the sulfur industry is sulfate acid. Its production accounts for about 60% of the sulfur that is mined. In the chemical industry, sulfur is used to convert rubber into high-quality rubber, that is, to vulcanize rubber. Sulfur is an essential component of any pyrotechnic mixtures. For example, match heads contain about 5%, and in the spread on the box - about 20% sulfur by weight. IN agriculture sulfur is used to control pests in vineyards. In medicine, sulfur is used in the manufacture of various ointments for the treatment of skin diseases.

Introduction

Every day we breathe in the air we need. Have you ever thought about what, more precisely, what substances the air consists of? Most of all it contains nitrogen (78%), followed by oxygen (21%) and inert gases (1%). Although oxygen does not make up the most basic part of the air, without it the atmosphere would be uninhabitable. Thanks to him, life exists on Earth, because nitrogen, both together and individually, is detrimental to humans. Let's look at the properties of oxygen.

Physical properties of oxygen

In the air, oxygen is simply not distinguishable, since under normal conditions it is a gas without taste, color and smell. But oxygen can be artificially converted into other aggregate states. So, at -183 o C it becomes liquid, and at -219 o C it hardens. But solid and liquid oxygen can only be obtained by a person, and in nature it exists only in a gaseous state. looks like this (photo). And hard like ice.

The physical properties of oxygen are also the structure of the molecule a simple substance. Oxygen atoms form two such substances: oxygen (O 2) and ozone (O 3). The model of an oxygen molecule is shown below.

Oxygen. Chemical properties

The first thing to start chemical characterization element - its position in periodic system D. I. Mendeleev. So, oxygen is in period 2, group 6, main subgroup number 8. Its atomic mass- 16 amu, it is a non-metal.

IN inorganic chemistry its binary compounds with other elements were combined into a separate one - oxides. Oxygen can form chemical compounds with both metals and non-metals.

Let's talk about getting it in the laboratories.

Chemically, oxygen can be obtained by decomposition of potassium permanganate, hydrogen peroxide, berthollet salt, active metal nitrates and heavy metal oxides. Consider the reaction equations for each of these methods.

1. Water electrolysis:

H 2 O 2 \u003d H 2 O + O 2

5. Decomposition of heavy metal oxides (eg mercury oxide):

2HgO \u003d 2Hg + O 2

6. Decomposition of nitrates of active metals (for example, sodium nitrate):

2NaNO 3 \u003d 2NaNO 2 + O 2

Application of oxygen

We are done with chemical properties. Now it's time to talk about the use of oxygen in human life. It is needed for fuel combustion in electrical and thermal power plants. It is used to produce steel from cast iron and scrap metal, for welding and cutting metal. Oxygen is needed for firefighters' masks, divers' cylinders, is used in ferrous and non-ferrous metallurgy, and even in the manufacture of explosives. also in Food Industry oxygen is known as food supplement E948. It seems that there is no industry where it is not used, but the most important role he plays in medicine. There he is called "medical oxygen". In order for oxygen to be usable, it is pre-compressed. The physical properties of oxygen contribute to the fact that it can be compressed. In this form, it is stored inside cylinders similar to these.

It is used in resuscitation and operations in equipment to maintain life processes in the body of a sick patient, as well as in the treatment of certain diseases: decompression, pathologies of the gastrointestinal tract. With its help, doctors save many lives every day. Chemical and physical properties oxygen contribute to the fact that it is used so widely.

Perhaps, among all the known chemical elements, it is oxygen that occupies a leading role, because without it, the emergence of life on our planet would simply be impossible. Oxygen is the most common chemical element on Earth, accounting for 49% of the total mass earth's crust. It is also included in earth's atmosphere, the composition of water and the composition of more than 1400 different minerals, such as basalt, marble, silicate, silica, etc. Approximately 50-80% of the total mass of tissues, both animals and plants, consists of oxygen. And, of course, its role for the breathing of all living things is well known.

History of the discovery of oxygen

People did not immediately comprehend the nature of oxygen, although the first guesses that some chemical element is the basis of air appeared as early as the 8th century. However, at that distant time there were neither suitable technical tools for its study, nor the possibility of proving the existence of oxygen as a gas responsible, among other things, for combustion processes.

The discovery of oxygen took place only a millennium later, in the 18th century, thanks to joint work several scientists.

• In 1771 the Swedish chemist Carl Scheele empirically studied the composition of air, and determined that air consists of two main gases: one of these gases was nitrogen, and the second, oxygen itself, although at that time the name “oxygen” itself had not yet appeared in science.
• In 1775, the French scientist A. Louvazier gave the name to Scheele's discovered gas - oxygen, which is also oxygen in Latin, the word "oxygen" itself means "producing acids".
• A year before the official "name day of oxygen", in 1774, the English chemist Priestley obtained pure oxygen for the first time by decomposition of mercury oxide. His experiments reinforce Scheele's discovery. By the way, Scheele himself also tried to obtain pure oxygen by heating saltpeter, but he failed.
• More than a century later, in 1898, the English physicist Joseph Thompson first made the public think that oxygen supplies could run out due to intense emissions of carbon dioxide into the atmosphere.
• In the same year, the Russian biologist Kliment Timiryazev, a researcher, discovers the property of plants to release oxygen.

Although plants release oxygen into the atmosphere, the problem posed by Thompson about a possible lack of oxygen in the future remains relevant in our time, especially in connection with intensive deforestation (oxygen suppliers), pollution environment, waste incineration and others. We wrote more about this in a previous issue. environmental issues modernity.

Importance of oxygen in nature

It was the presence of oxygen, combined with water, that led to the fact that life on our planet became possible. As we noted above, the main suppliers of this unique gas are various plants, including the largest number of the released oxygen is accounted for by underwater algae. They produce oxygen and some types of bacteria. Oxygen in the upper atmosphere forms an ozone layer that protects all inhabitants of the Earth from harmful ultraviolet solar radiation.

The structure of the oxygen molecule

An oxygen molecule is made up of two atoms, chemical formula looks like O 2 . How is an oxygen molecule formed? The mechanism of its formation is non-polar, in other words, due to the socialization of each atom by an electron. The bond between oxygen molecules is also covalent and non-polar, while it is double, because each of the oxygen atoms has two unpaired electrons at the outer level.

This is what an oxygen molecule looks like, due to its characteristics it is very stable. For many with her participation needed special conditions: heating, increased pressure, the use of catalysts.

Physical properties of oxygen

• First of all, oxygen is a gas that makes up 21% of air.
• Oxygen has no color, no taste, no smell.
• Can be dissolved in organic matter, absorbed by coal and powders.
• - The boiling point of oxygen is -183 C.
• The density of oxygen is 0.0014 g / cm 3

Chemical properties of oxygen

The main chemical property of oxygen is, of course, its support for combustion. That is, in a vacuum where there is no oxygen, fire is not possible. If, however, a smoldering torch is lowered into pure oxygen, it will ignite with new force. Combustion different substances it is a redox chemical process in which oxygen plays the role of an oxidizing agent. Oxidizing agents are substances that “take away” electrons from reducing substances. The excellent oxidizing properties of oxygen are due to its outer electron shell.

The valence shell of oxygen is located close to the nucleus and, as a result, the nucleus attracts electrons to itself. Oxygen also ranks second after fluorine on the Pauling electronegativity scale, for this reason, entering into chemical reactions with all other elements (with the exception of fluorine), oxygen acts as a negative oxidizing agent. And only by reacting with fluorine, oxygen has a positive oxidative effect.

And since oxygen is the second most powerful oxidizing agent among all the chemical elements of the periodic table, this also determines its chemical properties.

Obtaining oxygen

To obtain oxygen in laboratory conditions, the method of heat treatment of either peroxides or salts of acidic acids is used. Under the influence high temperature they decompose with the release of pure oxygen. Oxygen can also be obtained using hydrogen peroxide, even a 3% peroxide solution instantly decomposes under the action of a catalyst, releasing oxygen.

2KC l O 3 \u003d 2KC l + 3O 2 - this is how it looks chemical reaction receiving oxygen.

Also in industry, water electrolysis is used as another way to produce oxygen, during which water molecules decompose, and again pure oxygen is released.

The use of oxygen in industry

In industry, oxygen is actively used in such areas as:

• Metallurgy (when welding and cutting metals).
• Medicine.
• Agriculture.
• Like rocket fuel.
• For purification and disinfection of water.
• Synthesis of some chemical compounds including explosives.

Oxygen video

And finally, an educational video about oxygen.

When cutting metal, it is carried out by a high-temperature gas flame obtained by burning a combustible gas or liquid vapor mixed with commercially pure oxygen.

Oxygen is the most abundant element on earth found in the form of chemical compounds with various substances: in the earth - up to 50% by mass, in combination with hydrogen in water - about 86% by mass and in air - up to 21% by volume and 23% by mass.

Oxygen under normal conditions (temperature 20 ° C, pressure 0.1 MPa) is a colorless, non-combustible gas, slightly heavier than air, odorless, but actively supporting combustion. Under normal atmospheric pressure and a temperature of 0 ° C, the mass of 1 m 3 of oxygen is 1.43 kg, and at a temperature of 20 ° C and normal atmospheric pressure - 1.33 kg.

Oxygen has a high reactivity, forming connections with all chemical elements, except (argon, helium, xenon, krypton and neon). Reactions of the compound with oxygen proceed with the release a large number heat, i.e., are exothermic in nature.

When compressed oxygen gas comes into contact with organic matter, oils, fats, coal dust, combustible plastics, they can spontaneously ignite as a result of the release of heat during the rapid compression of oxygen, friction and impact of solid particles on metal, as well as electrostatic spark discharge. Therefore, when using oxygen, care must be taken to ensure that it does not come into contact with flammable and combustible substances.

All oxygen equipment, oxygen lines and cylinders must be thoroughly degreased. it is capable of forming explosive mixtures with combustible gases or liquid combustible vapors over a wide range, which can also lead to explosions in the presence of an open flame or even a spark.

The noted features of oxygen should always be kept in mind when using it in flame treatment processes.

Atmospheric air is mainly a mechanical mixture of three gases with the following volume content: nitrogen - 78.08%, oxygen - 20.95%, argon - 0.94%, the rest is carbon dioxide, nitrous oxide, etc. Oxygen is obtained by separating air on oxygen and by the method of deep cooling (liquefaction), along with the separation of argon, the use of which is continuously increasing at. Nitrogen is used as a shielding gas when welding copper.

Oxygen can be obtained chemically or by electrolysis of water. Chemical methods unproductive and uneconomical. At water electrolysis direct current Oxygen is obtained as a by-product in the production of pure hydrogen.

Oxygen is produced in industry from atmospheric air by deep cooling and rectification. In installations for the production of oxygen and nitrogen from air, the latter is cleaned of harmful impurities, compressed in a compressor to the corresponding pressure of the refrigeration cycle of 0.6-20 MPa and cooled in heat exchangers to a liquefaction temperature, the difference in the temperatures of oxygen and nitrogen liquefaction is 13 ° C, which enough for their complete separation in the liquid phase.

Liquid pure oxygen accumulates in the air separation apparatus, evaporates and collects in a gas holder, from where it is pumped into cylinders by a compressor at a pressure of up to 20 MPa.

Technical oxygen is also transported through the pipeline. The pressure of oxygen transported through the pipeline must be agreed between the manufacturer and the consumer. Oxygen is delivered to the place in oxygen cylinders, and in liquid form - in special vessels with good thermal insulation.

To convert liquid oxygen into gas, gasifiers or pumps with liquid oxygen evaporators are used. At normal atmospheric pressure and a temperature of 20 ° C, 1 dm 3 of liquid oxygen during evaporation gives 860 dm 3 of gaseous oxygen. Therefore, it is advisable to deliver oxygen to the welding site in a liquid state, since this reduces the tare weight by a factor of 10, which saves metal for the manufacture of cylinders, and reduces the cost of transporting and storing cylinders.

For welding and cutting according to -78 technical oxygen is produced in three grades:

• 1st - purity not less than 99.7%
• 2nd - not less than 99.5%
• 3rd - not less than 99.2% by volume

The purity of oxygen has great importance for oxygen cutting. The less gas impurities it contains, the higher the cutting speed, cleaner and less oxygen consumption.