Oxygen, the non-metallic element of the 16th group in the second period of the periodic table, element symbol O, atomic number 8, relative atomic mass 15.9994.[5]
Oxygen is the most abundant and widely distributed element in the crustBiosphereThe content of the most important element in the crust is 48.6%.Simple oxygen accounts for 20.9% in the atmosphere.[1]
The oxygen density is 1.404g/L, the liquid relative density is 1.149 (- 183 ℃), the solid relative density is 1.426 (- 252.5 ℃), the melting point is - 218.79 ℃, and the boiling point is - 182.95 ℃.Oxygen is insoluble in water, ethanol and organic solvents. Its electronegativity is second only to fluorine. All chemical elements can combine with oxygen directly or indirectly to form various oxides;exceptinert gas、halogenAnd some inactive metals (such asgold、platinumIn addition, oxygen can react directly with all metals and nonmetals.It can form peroxides and superoxide with active metals.Laboratory availablePotassium chlorateorpotassium nitrateThermal decomposition preparation, or thermal decomposition of heavy metal oxide or reaction of metal peroxide with water and acid;In industry, it is prepared by liquid air fractionation.[5]
Oxygen is necessary for animals to maintain life and combustion processes, and is also widely used in metallurgy, chemical industry, environmental protection and other fields.[5]
In 2023, scientists first created an oxygen isotope containing 8 protons and 20 neutrons: oxy-28.[7]
Chinese name
oxygen
Foreign name
Oxygen
molecular weight
32 (Note: the oxygen molecule has two atoms, and the atomic weight of oxygen is 16)
French chemist in 1777LavoisierPropose flamingOxidation theory, pointing out that substances can only be burned in oxygen containing air, and the increase in the weight of combustibles is equal to the loss of oxygen in the air, thus overthrowing all the phlogiston theory and formally establishingLaw of conservation of mass。Strictly speaking, it is found that the oxygen element isSwedenChemist Scheler, while determining the oxygen elementchemical propertyFrench chemist Lavoisier.[2]
The honor gained from the discovery of oxygen was shared by three chemists: an Englishman, a Swede, and a Frenchman.Joseph PriestleyHe was the first person to issue the statement of oxygen element. In 1774, from focusing on sunlight toMercuric oxide(HgO), and then collect the released gas.He noticed that the candles burned brighter here and made breathing easier.What Priestley didn't know was that,Carl Wilhelm Scheele Carl Wilhelm Scheele made oxygen in June 1771.He wrote down a description of his discovery, but it was not released until 1777.LavoisierHe also claimed to have discovered oxygen, and he proposed that this new gas be called oxy-g è ne, which means to form acid, because he believed that this element was allAcidsThe foundation of.
On May 16, 2018, Osaka University of Technology, Japan National Astronomical Observatory andNagoya University The team formed by, among others, announced that using the ALMA radio telescope in Chile, South America, oxygen was found in the Milky Way in the direction of Leo 13.28 billion light years away from Earth.[3]
In 2023, Yosuke Kondo team of Tokyo University of Technology and researchers from many countries first created an oxygen isotope containing 8 protons and 20 neutrons: oxy-28 by crushing the high-energy beam of fluorine atoms into liquid hydrogen.[7]
Physical and chemical properties
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physical property
Liquid oxygen
oxygen（Oxygen）It is a chemical element with atomic number of 8, relative atomic mass of 15.9994 and oxygen atomic radius of 0.074 nm..It is indicated by the symbol "O".stayperiodic table of ele mentsIn, oxygen is a member of oxygen group elements, and it is also a highly reactive non-metallic element in the second cycle. It is easy to form compounds (mainly oxides) with almost all other elements.stayStandard statusTwo oxygen atoms combine to form oxygen, which is a colorless, odorless and tasteless diatomic gas with the chemical formula of Otwo。If calculated by mass, the content of oxygen in the universe is second only tohydrogenandheliumIn the crust, oxygen is the most abundant element.Oxygen accounts for 89% of water mass and 20.9% of air volume.[2]
Valence of oxygen: The valence of oxygen is very special, generally - 2 and 0.Oxygen is usually - 1 in peroxides.staySuperoxide- 1/2 in the middle,Ozone oxideThe intermediate oxygen is - 1/3, and the valence here is called apparent valence, which means that the apparent valence has no actual meaning. The valence of oxygen in superoxide can only be said to beSuperoxide radicalIons, you can't look at eachatom, because the electron isquantizationThat is, it is discontinuous, there is no 1/2 electron, and there is no natural valence of 0.5. The same is true for ozone. In the peroxy radical, there are two electrons that form an electron pair, so these two electrons do not show valence, so the peroxy radical ion as a whole shows - 2 valence.The positive value of oxygen seldom appears, only in the compounds with fluorineOxygen difluoride，Dioxygen difluoride andFluoroplatinic acid oxygen(O ₂ PtF ₆).[2]
Belongs to in the periodic table of elementsⅥ Group A elements, the valence is generally 0 and - 2.Most elements can form oxides when heated in an oxygen containing atmosphere.Many elements can form more than one oxide.Oxygen moleculeAt low temperatures, hydrated crystals O ₂ · H ₂ O and O ₂ · H ₂ O ₂ can be formed, the latter is more unstable.The solubility of oxygen in water is 4.89 ml/100 ml water (0 ℃), which is the basis of life in water.Oxygen in the crustabundanceFirst place.The dry air contains 20.946% oxygen by volume;Water is composed of 88.81% oxygen by weight.exceptsixteenO In addition, there areseventeenO andeighteenO etcisotope。[2]The common oxidation states are - 1, - 2, 0.The covalent radius is 66 pm, the first ionization potential is 1314kJ/mol, and the electronegativity is 3.44.
Preparation method
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Laboratory method
1. Heating potassium permanganate or potassium manganate:
Manganese dioxide and hydrogen peroxide reaction device
Industrial process
Liquid air separation method
Pressurize at low temperature to change air into liquid, and then evaporate. Since the boiling point of liquid nitrogen is - 196 ℃, which is lower than that of liquid oxygen (- 183 ℃), nitrogen first evaporates from liquid air, and the rest is mainly liquid oxygen.
The main components of air are oxygen and nitrogen.The method of air separation for preparing oxygen scale from air is based on the different boiling points of oxygen and nitrogen.First, precool and purify the air (remove a small amount of moisture, carbon dioxideacetylene、hydrocarbonAnd other impurities such as gas and dust), and then compressed and cooled to make it liquid air.Then, taking advantage of the different boiling points of oxygen and nitrogen, liquid air is evaporated and condensed for many times in the distillation tower to separate oxygen and nitrogen to obtain pure oxygen (up to 99.6% purity) and pure nitrogen (up to 99.9% purity).If some additional devices are added, they can also be extractedargon、neon、helium、krypton、xenonSuch as rare inert gas with very little content in the air.The oxygen produced by the air separation device is compressed by the compressor, and then the compressed oxygen is stored in a high-pressure cylinder, or directly transported to the factory and workshop through pipes.Using this method to produce oxygen requires large complete sets of equipment and strict safe operation technology, but the output is high, thousands of cubic meters of oxygen can be produced per hour, and the raw materials used are only air that does not need to be bought, transported or stored in warehouses. Therefore, since the first cryogenic air separation oxygen generator was developed in 1903,This method of oxygen production has been the most widely used.
Membrane separation technology
Membrane separation technology has developed rapidly.By using this technology, under a certain pressure, air can pass through the film with oxygen enrichment function to obtain oxygen enriched air with high oxygen content.Using this membrane for multistage separation, oxygen enriched air with more than 90% oxygen can be obtained.
Molecular sieve oxygen production method (adsorption method)
Using the characteristic that nitrogen molecule is larger than oxygen molecule, special molecular sieve is used to separate oxygen from the air.First, use the compressor to force the dry air through the molecular sieve into the vacuum absorber. The nitrogen molecules in the air are adsorbed by the molecular sieve, and the oxygen enters the absorber. When the oxygen in the absorber reaches a certain amount (pressure reaches a certain level), the oxygen outlet valve can be opened to release oxygen.After a period of time, the nitrogen adsorbed by the molecular sieve gradually increases, the adsorption capacity decreases, and the purity of the oxygen produced decreases. It is necessary to use a vacuum pump to extract the nitrogen adsorbed on the molecular sieve, and then repeat the above process.This method of producing oxygen is also called adsorption method. A small oxygen generator using adsorption method has been developed, which is convenient for home use.
Electrolytic oxygen
Put water into the electrolytic cell and addsodium hydroxideorPotassium hydroxideTo improve the electrolysis degree of water, and then connect the DC power, the water will be decomposed into oxygen and hydrogen.For every cubic meter of oxygen produced, two cubic meters of hydrogen are obtained.The electricity consumption for producing one cubic meter of oxygen by electrolysis is 12-15 kilowatt hours, which is very uneconomical compared with the power consumption of the above two methods (0.55-0.60 kilowatt hours).Therefore, electrolysis method is not suitable for large amount of oxygen production.In addition, if the hydrogen produced at the same time is not collected properly, it will gather in the air, such as mixing with oxygen, and will easily cause extremely violent explosion.Therefore, electrolysis method is not applicable to household oxygen production.
Oxygen accounts for 48.6% of the mass of the whole crust, which is the most abundant element in the crust. It basically exists in the form of oxygen compounds in the crust.Each kilogram of seawater has 2.8 mg of oxygen dissolved in it, and the oxygen element in seawater has reached 89%.For the whole earth, the mass fraction of oxygen is 15.2%.No matter people, animals or plants, their cells have similar composition, in which oxygen accounts for 65% of the mass.In the air, the volume of oxygen accounts for 20.9%.
Toxicological data
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Although oxygen is good for the body, the more the better, also occurs when the oxygen content is too highOxygen poisoning，[4]There are three main types of oxygen poisoning:
Pulmonary oxygen poisoning
Similar to bronchopneumonia.Its performance and general development process are: similar at firstupper respiratory tract infectionThe symptoms of tracheal irritation, such as poststernal discomfort (irritation or burning sensation) with mild dry cough, are slowly aggravated;Then there was post sternal pain, and the pain gradually spread along the bronchial tree to the whole chest, especially when inhaled;The pain gradually worsens and uncontrollable cough occurs;Breathing difficulties are also associated with rest.Ending exposure at an early stage of symptom onset, chest pain and cough can be alleviated within hours.
Cerebral oxygen poisoning
Fibrous tremors of the forehead, eyes, nose, lips and cheek muscles initially appear, which can also affect the small muscles of the hand;Pale and smelly.Then there may be nausea, vomiting, dizziness, sweat, salivation, upper abdominal tension;There may also be loss of vision, narrowing of visual field, illusion and auditory hallucination;There will also be bradycardia, palpitations, choking, numbness at the finger (toe) end, abnormal emotions (anxiety, depression, irritability or joy).Then extreme fatigue, lethargy, dyspnea, etc.In a few cases, collapse may occur.
Ocular oxygen poisoning
The main manifestation is retinal atrophy.Premature infants take oxygen in the incubator for too long, and the retina has extensive vascular obstruction, fibrous tissue infiltration, and post crystal fiber hyperplasia, which can cause blindness.
Storage and transportation
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Place it in a pressure resistant cylinder and store it below 35 ℃.
test method
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source
This product contains OtwoNot less than 99.5% (mL/mL).
character
This product is colorless gas, odorless, tasteless, and has strong combustion supporting power.
The product 1 can be dissolved in 7 volumes of ethanol or 32 volumes of water at 20 ° C under normal pressure.
identify
This product can make the red wood burst into flames.
inspect
PH
Take 0.3 mL of methyl red indicator solution and 0.3 mL of bromothymol blue indicator solution respectively, add 400 mL of water, boil for 5 minutes, cool down, take 100 mL of each, place them in three colorimetric tubes A, B and C, add 0.20 mL of hydrochloric acid titrant (0.01 mol/L) in tube B, add 0.40 mL of hydrochloric acid titrant (0.01 mol/L) in tube C, and then pass 2000 mL of this product in tube B (the speed is 4000 mL per hour),The color of tube B shall not be darker than the red of tube C or the green of tube A.
carbon monoxide
Take two colorimetric tubes A and B, respectively add 25mL of ammonia silver nitrate test solution at low temperature. After 1000mL of this product is passed through tube A (the speed is 4000mL per hour), it should be clear and colorless compared with tube B.
carbon dioxide
Take two colorimetric tubes A and B, respectively add 100mL of 5% barium hydroxide solution, 1.0mL of 0.04% sodium bicarbonate solution in tube B, 1000mL of the product in tube A (at a rate of 4000mL per hour), and the turbidity shown shall not be thicker (0.01%) than that in tube B.
Other gaseous oxidizing substances
Take 100mL of newly prepared potassium iodide starch solution (take 0.5g of potassium carbide, add 100mL of starch indicator solution to dissolve it), place it in a colorimetric tube, add 1 drop of acetic acid, pass 2000mL of this product (the speed is 4000mL per hour), and the solution should be colorless.
Assay
Instrumentation
As shown in the figure: A and C are absorbers with a total capacity of about 300mL, B are suitable stoppers, D, E and I are fine glass tubes, F is the main body of the measuring tube with a scale precision of 0.1mL and a capacity of 100mL, G is a three-way piston, H is the gas inlet and outlet, and J is a balance bottle.Before use, use a rubber tube to connect the absorber with the gas measuring tube, and then connect the latter with the balance bottle.
Instrumentation
Assay
First, fill the copper wire joint (take a red copper wire with a diameter of about 0.8mm and wind it into a copper wire roll with a diameter of about 4mm and cut it into a small section with a diameter of about 10mm) into the absorber A, plug it with plug B, and then introduce the ammonia ammonium chloride solution (take 150g of ammonium chloride, add 200mL of water, add 200mL of concentrated ammonia solution carefully while stirring, and mix it well), so that A is filled and part of it is left in C, and then inject the saturated sodium chloride solution into the balance bottle J,Raise the balance bottle so that the saturated sodium chloride solution is filled with F, and the excess solution flows out from H. Turn G to connect the arch gas pipe and the absorber. Lower the balance bottle so that the solution in the absorber is fully filled with the inlet of the tubes D, E, I and piston G. Close the piston immediately. If there is gas and part of ammonia ammonium chloride solution entering the gas measuring pipe, raise the balance bottle to rotate the piston so that it can be discharged from H.
Connect the test cylinder to the pressure reducing valve (specially for oxygen gas), connect the rubber pipe to the outlet of the latter, carefully slightly open the cylinder gas valve, and then open the pressure reducing valve to allow oxygen to blow out for 1 minute, then adjust it to a weaker airflow.
Connect the other end of the rubber tube to the gas inlet and outlet H. After the gas measuring tube is filled with this product, close G and immediately remove the rubber tube on the gas inlet and outlet H. Leave it still for a few minutes, turn G to connect the gas inlet and outlet H, and slowly raise and lower the balance bottle (in order to prevent inhalation of external air, pay attention to making the liquid level in the balance bottle slightly higher than the liquid level in the gas measuring tube),Make the liquid level in the measuring tube reach the scale of 100mL.Turn G to connect the gas measuring tube and the absorber, lift the balance bottle so that the test article enters the absorber A. When the saturated sodium chloride solution flows through the catheter I and fills the catheter D, close G and carefully shake the absorber A fully for 5 to 10 minutes. When the gas is absorbed nearly completely (the remaining is nitrogen or other non absorbed gas), turn G to connect the gas measuring tube and the absorber, and lower the balance bottle,Transfer the residual gas from the absorber to the gas measuring pipe. When the ammonia ammonium chloride solution fills the absorber A and passes through the piston G through the tubes D, E and I, close the piston.
After about 5 minutes, adjust the liquid level of the balance bottle so that the gas pressure in the measuring tube is consistent with the atmospheric pressure, read the liquid level scale in the measuring tube, and calculate the content of the test article.
In order to check whether the oxygen is completely absorbed, the above operation should be repeated, starting from "turning G to connect the gas measuring tube and absorber, lifting the balance bottle", and operating according to the law until the volume of the remaining gas is constant (the secondary difference is not more than 0.05mL).
Before inspection or measurement, the test sample cylinder shall be placed at the laboratory temperature for more than 6 hours.
category
It is used for prevention and treatment of hypoxia.
