The chemical formula is NatwoCOthree, commonly known as soda, soda ash, soda ash, disodium carbonate, soda ash, usually white powder, strong electrolyte, density of 2.532g/cm3, melting point of 851 ° C, easily soluble in water and glycerin, slightly soluble in anhydrous ethanol, and hardly soluble in propanol[10], which has the common property of salt and belongs to inorganic salt.Damp air will absorb moisture and agglomerate, and part of it will become sodium bicarbonate.Sodium carbonate can be produced by the combined method[12]Ammonia alkali method[11], Leblanc[13]It can also be refined by natural alkali processing.As an important inorganic chemical raw material, it is mainly used in the production of flat glass, glass products and ceramic glazes.It is also widely used in domestic washing, acid neutralization and food processing.In terms of the environment, sodium carbonate is generally regarded as a relatively harmless substance to the ecosystem.However, a large amount of discharge may still affect the pH value and total alkalinity of the water body, so proper management and supervision are required during use and treatment.
The research and application of sodium carbonate has a long history.Before the artificial synthesis of soda ash, the ancient Egyptians had used natural sodium carbonate in the manufacture of glass. In addition, in ancient times, it was found that some seaweeds, after being dried in the air, contained alkalis in the ashes, which could be soaked in hot water and filtered to obtain brown lye for washing.A large amount of natural alkali comes from minerals, mainly underground or alkaline lakes.The natural alkali ore existing in the sedimentary layer has the highest grade and is widely distributed.The first method of artificial synthesis of soda ash was invented at the end of the 18th century. France Lubrand reduced and carbonated mirabilite with limestone and coal at high temperature to obtaintwoThe crude product dominated by CO3 black ash is leached, evaporated, refined, recrystallized and dried to obtain heavy soda ash with a purity of about 97%[5]。In 1791, Leblanc obtained the patent right.In the same year, the Duke of Orleans of France raised funds to build the first Lubrand Soda Plant in Saint Denis near Paris.In 1823, Britain abolished the salt tax and introduced Lubumbanfa. A soda ash factory was built in Liverpool and put into production.The period from 1825 to 1880 was the heyday of the Lubrand process.This alkali production method has driven the production of a series of chemical products such as sulfuric acid, hydrochloric acid bleaching powder, mirabilite and sulfur. It has also played a huge role in promoting the emergence of gas scrubbers, rotary ovens, mechanical ovens, open type Teflon pans and Shank type leaching devices.Leblanc is an important milestone in the rise of soda ash industry.However, the purity of soda ash produced by this method is low, the production cost is high, the labor efficiency is low, and it is difficult to operate continuously. In addition, the recovered hydrochloric acid is highly corrosive and must be sold or treated separately, which makes the demand for exploring new soda production methods always exist[9]。1861, BelgiumErnest Solvay He independently invented soda ash and obtained a patent.Since the protection of technical secrets has not been widely applied, it was only in the 1920s that a breakthrough was made from the United States, especially the famous Chinese chemical expertsHou DebangPublished in 1932《Soda manufacturing》A book, which will be kept secret for 70 years, was published by Solvay.Hou Debang also createdHou's soda processAnd set up a pilot plant in Sichuan.In 1952, a joint alkali workshop was set up in Dalian Chemical Plant.Asahi Glass The NA method introduced is essentially a compromise method between combined alkali and ammonia alkali.Free adjustment of soda ash andammonium chlorideProportion of[5]。
Sodium carbonate crystallization
Physical and chemical properties
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physical property
character
White odorless powder or particle under normal temperature
density
2.532 g/cm³
melting point
851℃
Solubility
Easily soluble in water, also soluble in glycerin, 20 grams of sodium carbonate can be dissolved per 100 grams of water at 20 ℃, the highest solubility is at 35.4 ℃, 49.7 grams of sodium carbonate can be dissolved in 100 grams of water, slightly soluble inAnhydrous ethanol, insoluble inPropanol
Aqueous solution PH
11.5 for 1% aqueous solution
aqueous solution
It can conduct electricity in aqueous solution or molten state, and the aqueous solution has astringency and greasy feeling
Water absorption
With water absorption, it gradually absorbs 1mol/L of water (about=15%) in the exposed air
hydrate
NatwoCOthree·HtwoO，NatwoCOthree·7HtwoO and NatwoCOthree·10HtwoO[6]
chemical property
The aqueous solution of sodium carbonate is alkaline and corrosive to a certain extent. It can double decompose with acid, and can also react with someCalcium saltBarium salt undergoes double decomposition reaction.The solution is alkaline and can make phenolphthalein red.
stability
Strong stability, but it can also be decomposed at high temperature to generateSodium oxideandcarbon dioxide：
Long term exposure to the air can absorb moisture and carbon dioxide in the air and generatesodium bicarbonate, and agglomerate:
Crystalline hydrate of sodium carbonatetwoCOthree·10HtwoO) Easily weathered in dry air:
Because sodium carbonate is in aqueous solutionhydrolysis，ionizationOutgoingCarbonateIons and waterHydrogen ionJunction synthesisBicarbonateIons, leading to the reduction of hydrogen ions in the solution, leaving ionizedHydroxyl ion, so the solutionpHIt is alkaline.
Because carbonate can combine with protons (i.e. hydrogen ions) in water to generate bicarbonate andcarbonic acidAnd can combine protons in acid to release carbon dioxide.So sodium carbonateAcid base proton theoryIt belongs to Bronsted base.
React with acid
Take hydrochloric acid as an example.When hydrochloric acid is sufficientsodium chlorideandcarbonic acidThe unstable carbonic acid immediately decomposes into carbon dioxide and water.This reaction can be used to prepare carbon dioxide:[2]
Sodium carbonate can undergo double decomposition reaction with calcium salt, barium salt, etc. to generate precipitation and new sodium salt:
As sodium carbonate hydrolyzes in water to form sodium hydroxide and carbonic acid, its reaction with some salts will promote the chemical balance to move in the positive direction, generating corresponding alkali and carbon dioxide:
Preparation method
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Laboratory methods
Laboratory preparation of sodium carbonate:
。
Leblanc process
As early as 1791, the ancients began to use salt, sulfuric acid, coal and limestone as raw materials to produce sodium carbonateLeblanc process 。
The raw materials of this method are not fully utilized, the working conditions are poor, and the product quality is poorsolvay process Replace.
Soda production by Soxhlet method
In 1859, BelgiansSolvay , usingsalt、ammonia、carbon dioxideAs raw material, it precipitates from the solution at room temperaturesodium bicarbonateIt is heated and decomposed into sodium carbonate. This method is called Soxhlet method, which has been used until now[15]。
Ammonia reacts with water and carbon dioxide to form one moleculeAmmonium bicarbonate, this is the first step:
The second step is: ammonium bicarbonate andsodium chlorideReactivesodium bicarbonatePrecipitation and ammonium chloride, sodium bicarbonate precipitate because of its low solubility.Sodium bicarbonate solid obtained through filtration:
The total chemical equation of these two steps is:
Step 3: heating and decomposing sodium bicarbonate to generate water, carbon dioxide and sodium carbonate, which is the soda ash we need:
Hou Debang, a Chinese who returned from studying abroad in 1943, improved the Solvay process in combination with the situation of salt shortage in mainland China, combining soda ash and synthetic ammonia industries to produce sodium carbonate and ammonium chloride fertilizer at the same time, greatly improving the utilization rate of salt[16]。
First, ammonia reacts with water and carbon dioxide to form one molecule ofAmmonium bicarbonate, the second step is ammonium bicarbonate andsodium chlorideReactivesodium bicarbonateSedimentation andammonium chlorideSodium bicarbonate precipitates because of its low solubility.Sodium bicarbonate solid is obtained through filtration.(These two steps are the same as the Soxhlet process above).
In the third step, the part of sodium bicarbonate synthesized can be sold directly from the factory, and the rest of sodium bicarbonate will be heated and decomposed to produce sodium carbonate, and the carbon dioxide generated can be recycled back to the first step.
Hou's caustic soda production process
According to NHfourThe principle that the solubility of Cl is greater than that of NaCl, but lower than that of NaCl at low temperature is that at 278K~283K (5 ℃~10 ℃), fine salt powder is added to the mother liquor to make NHfourCl crystallizes separately for nitrogen fertilizer.
The difference between Soxhlet method and Hough method is that NHthreeIt is recycled. During the whole production process, COtwoRecycled, NHfourCl is directly used as fertilizer, a by-product of soda ash.Therefore, the product of Soxhlet method is sodium carbonate, a by-productcalcium chloride；The product of Hou's process is sodium carbonate, a by-productammonium chloride。
Advantages of this method: the advantages of ammonia alkali method are retained, and its disadvantages are eliminated, so that the utilization rate of table salt is increased to 96%;NHfourCl can be used as nitrogen fertilizer;It can be combined with the ammonia plant to convert CO, the feed gas of ammonia, into COtwo, eliminating CaCOthreeCO productiontwoThis process.
Sodium carbonate is one of the important chemical raw materials, which is widely used in light industry, daily chemical industry, building materials, chemical industry, food industry, metallurgy, textile, petroleum, national defense, medicine and other fields. It is also used as the raw material, cleaning agent, detergent for manufacturing other chemicals, as well as in photography and analysis fields.Next are metallurgy, textile, petroleum, national defense, medicine and other industries.The glass industry is the largest consumer of soda ash, consuming 0.2 tons of soda ash per ton of glass.Among industrial soda ash, light industry, building materials and chemical industry account for about 2/3, followed by metallurgy, textile, petroleum, national defense, medicine and other industries[8]。
1. The glass industry is the largest source of consumption of soda ash, which consumes 0.2t of soda ash per ton of glass.Mainly used for float glass, picture tube glass shell, optical glass, etc.
2. Used in chemical industry, metallurgy, etc.The use of heavy soda ash can reduce the flying of alkali dust, reduce the consumption of raw materials, improve the working conditions, improve the product quality, reduce the erosion of alkali powder on refractory materials, and extend the service life of the furnace.
3. As a buffer, neutralizer and dough improver, it can be used for cakes and flour food, and can be used moderately according to production needs.
4. As a detergent, it is used for wool rinsing, bath salt and medicine, and as an alkaline agent in tanning.
5. It is used in food industry as neutralizer and leavening agent, such as manufacturing amino acid, soy sauce and flour products such as steamed bread and bread.It can also be added into pasta to increase elasticity and ductility.Sodium carbonate can also be used to produce monosodium glutamate
6. Special reagent for color TV
7. It is used in pharmaceutical industry as antacid and osmotic laxative.
8. It is used for chemical and electrochemical oil removal, chemical copper plating, aluminum etching, electrolytic polishing of aluminum and alloy, chemical oxidation of aluminum, sealing after phosphating, rust prevention between processes, electrolytic chromium removal and chromium oxide film removal, and also used in the electrolytic solution of pre copper plating, steel plating, and steel alloy plating
9. Metallurgical industry is used as smelting flux, flotation agent for mineral processing, and steelmaking and antimony smelting are used as desulfurizers.
10. Printing and dyeing industry is used as water softener.
11. The leather industry is used for degreasing raw hides, neutralizing chrome tanned leather and improving the alkalinity of chrome tanning liquor.
12. Quantitative analysis is used to determine the benchmark of acid solution.Determination of aluminium, sulphur, copper, lead and zinc.Urine and blood glucose were examined.Analysis of silica as a cosolvent in cement.Metallographic analysis of metal, etc.
Safety measures
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danger
Sodium carbonate dust is irritating to the skin, respiratory tract and eyes. Long term contact with this solution may cause eczema, skin softening, dermatitis, etc.
Fire fighting measures
In case of fire, water, dry powder extinguishing agent, foam or carbon dioxide can be used for rescue.
First aid measures
Contact part
First aid measures
Skin contact
Take off contaminated clothes immediately, wash with plenty of flowing water for at least 15 minutes, and then seek medical advice.
Eye contact
Immediately lift the eyelids, wash them with plenty of water or physiological saline for at least 15 minutes, and then seek medical advice[7]。
inhalation
Move away from the site to a place with fresh air for rest. If breathing is difficult, carry out oxygen transfusion, and then seek medical advice.
Ingestion
Rinse with water, drink milk or egg white, and then seek medical advice.
Four Soda Brothers
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soda
Soda is a transliteration of Soda, with the chemical formula NatwoCOthree。It has many names, which are called sodium carbonate in science and soda ash in common use.It is called hydrated sodium carbonate with crystal waterSodium carbonate monohydrate（NatwoCOthree·HtwoO）、Sodium carbonate heptahydrate (NatwoCOthree·7HtwoO) AndSodium carbonate decahydrate（NatwoCOthree·10HtwoO) Three.
Of the three types of soda, sodium carbonate is the most widely used.It is a very important chemical product and an important raw material for glass, soap, textile, paper making, leather and other industries.It is also used in metallurgical industry and purified water.It can also be used in the manufacture of other sodium compounds.As early as the 18th century, it, together with sulfuric acid, hydrochloric acid, nitric acid and caustic soda, was one of the basic chemical raw materials - three acids and two bases.In daily life, soda also has many uses. For example, it can be directly used as a detergent. When steaming steamed bread, some soda can neutralize the acidic substances produced during fermentation.
baking soda
Sodium bicarbonate
The chemical formula of baking soda is NaHCOthree。It also has many scientific namessodium bicarbonate, and weigh sodium carbonate or acid sodium carbonate.Besides baking soda, baking soda, fermented soda and heavy soda are also commonly known.
Sodium bicarbonate is white crystal, soluble in water, and the aqueous solution is weakly alkaline.
In hot air, it can slowly decompose and release some carbon dioxide;When heated to 270 ℃, carbon dioxide is completely liberated:
It can also interact with acids (e.ghydrochloric acid）Action emits carbon dioxide:
These properties of baking soda make it have many important uses in production and life.In the fire extinguisher, it is one of the raw materials to produce carbon dioxide;In the food industry, it is a main raw material of fermented powder;It is also a commonly used raw material in the manufacture of cool drinks;In medical treatment, it is a kind of medicament for treating hyperacidity.
Sodium bicarbonate is colorless and transparent crystal, which is easily soluble in water, and the aqueous solution is weakly alkaline.It is weathered in dry air above 33 ℃ and loses crystal water.
It is relatively stable in neutral and alkaline solutions and rapidly decomposes in acidic solutions:
Sodium bicarbonate has strong complexing ability and can form complex with silver bromide:
According to this property, it can be used as fixing agent.During phase washing, the excess sodium bicarbonate reacts with the silver bromide in the non photosensitive part of the negative and converts it into soluble
Remove AgBr to fix the developing part.
Big soda also has strong reducibility, which can reduce chlorine and other substances:
Therefore, it can be used as dechlorination agent for cotton fabric after bleaching.Similarly, iodine stains on fabrics can also be removed.In addition, soda is also used for tanning leather, electroplating and extracting silver from ores.
Smelly soda
The above three kinds of soda are commonly used.In addition, sometimes "smelly soda" will be mentioned.
Sodium sulfide
Stinky soda isSodium sulfideCommon name of, chemical formula is NatwoS，It is also called stink alkali, yellow alkaliAlkali sulfide, with odor.Soluble in cold water, extremely soluble in hot water, slightly soluble in alcohol.
Sodium sulfide is an inorganic compound, and pure sodium sulfide is a colorless crystalline powder.It is highly hygroscopic and easily soluble in water.The aqueous solution shows strong alkaline reaction.Contact with skin and hair can cause burns.Therefore, sodium sulfide is commonly known as alkali sulfide.
Sodium sulfide may explode due to impact or sharp heating. Its chemical property is unstable, and it will release toxic substances in case of acidhydrogen sulfideGas:
Sodium sulfide can be used in the production of dye industrySulfur dyeIt is the raw material of blue sulfide and blue sulfide.The printing and dyeing industry is used as a dyeing aid for dissolving sulfur dyes.In leather industry, it is used to hydrolyze raw hides to remove hair, and in paper industry, it is used as a cooking agent for paper.It can also be used as a mordant for cotton fabric dyeing in textile industry and as an antipyretic in pharmaceutical industry.Sodium sulfide can also be used for the treatment of conductive layer in direct electroplating. The purpose of forming a good conductive layer on the non-metallic surface is achieved by reacting sodium sulfide with palladium to generate colloidal palladium sulfide.
