Thread Content
This post was last edited by Xiao Hai’s Home on 2021-2-4 at 13:47. Introduction: Sodium carbonate is an inorganic compound with the molecular formula Na₂CO₃ and a molecular weight of 105.99. It is also known as soda ash, but it is classified as a salt rather than an alkali. In international trade, it is also known as soda or alkali ash. It is an important inorganic chemical raw material, mainly used in the production of flat glass, glass products, and ceramic glazes. It is also widely used in household cleaning, acid neutralization, and food processing. Before the synthetic production of soda ash, it was discovered in ancient times that certain seaweeds, after being dried, contained alkalis in their ashes; by soaking these ashes in hot water and filtering the result, a brown alkaline solution could be obtained for use in washing. A large amount of natron comes from minerals, mainly found in underground deposits or alkaline lakes. Trona minerals occurring in sedimentary layers have the highest grade and are widely distributed. The earliest method for synthesizing soda ash was invented at the end of the 18th century; in France, Rouelle used mirabilite together with limestone and coal, subjecting them to reduction and carbonation at high temperatures to obtain a crude product containing mainly Na2CO3 – known as \"black ash\". Through processes such as leaching, evaporation, purification, recrystallization, and drying, soda ash with a purity of around 97% could be obtained. In 1861, E. Solvay from Belgium independently invented soda ash and obtained a patent for it. Due to the fact that the protection of trade secrets had not been widely applied, progress was made in the United States only in the 1920s. In particular, the renowned Chinese chemical engineer Hou Debang published the book \"The Production of Soda Ash\" in 1932, revealing the Solvay process that had been kept secret for 70 years. Hou Debang also developed the Hou process for soda production between 1939 and 1942, and established a pilot plant in Sichuan. In 1952, a combined alkali production workshop was established at the Dalian Chemical Plant. The NA process introduced by Nippon Asahi Glass Company is essentially a compromise between the double-alkali and ammonia-alkali processes. The ratio of soda ash to ammonium chloride can be adjusted as desired. Properties: Sodium carbonate is a white, odorless powder or granules at room temperature. It is absorbent and gradually absorbs 1 mol/L of moisture (approximately 15%) when exposed to air. Its hydrates include Na2CO3·H2O, Na2CO3·7H2O, and Na2CO3·10H2O. Solubility: Sodium carbonate is readily soluble in water and glycerin. At 20°C, 20 grams of sodium carbonate can dissolve in every 100 grams of water; the solubility is highest at 35.4°C, with 49.7 grams of sodium carbonate able to dissolve in 100 grams of water. It is slightly soluble in anhydrous ethanol and poorly soluble in propanol. An aqueous solution of sodium carbonate is alkaline and has a certain degree of corrosiveness; it can undergo double-displacement reactions with acids, as well as with certain calcium and barium salts. The solution is basic and can turn phenolphthalein red. Stability: It has good stability, but it can also decompose at high temperatures, producing sodium oxide and carbon dioxide: https://bkimg.cdn.bcebos.com/formula/3f6acc7bff2cf64656c77b900bba6a7f.svg When exposed to air for an extended period, it absorbs moisture and carbon dioxide from the air, forming sodium bicarbonate and resulting in the formation of hard lumps: https://bkimg.cdn.bcebos.com/formula/102799604a49682aa77b92ec41f667b1.svg The crystalline hydrate of sodium carbonate, soda ash (Na2CO3·10H2O), tends to weather easily in dry air: https://bkimg.cdn.bcebos.com/formula/39ffbbc5cb129e1000d26e4d675ed666.svg Thermodynamic properties: At (298.15 K, 100 K), its thermodynamic properties are as follows: State: Solid. Standard molar enthalpy of formation: https://bkimg.cdn.bcebos.com/formula/c5c81452b98e93a10a42d1e8df9dc64c.svg –1130.8 kJ·mol-1. Standard molar Gibbs free energy of formation: https://bkimg.cdn.bcebos.com/formula/35163273bc23f4a39304f9eb8bc14113.svg –1048.1 kJ·mol-1. Standard entropy: https://bkimg.cdn.bcebos.com/formula/8eb8f1f5d970c73940d8435a37591947.svg 138.8 J·mol-1·K-1. Hydrolysis reaction: Sodium carbonate undergoes hydrolysis in aqueous solutions; the carbonate ions produced through ionization combine with hydrogen ions in water to form bicarbonate ions, thereby reducing the concentration of hydrogen ions in the solution. This results in an alkaline pH for the solution. https://bkimg.cdn.bcebos.com/formula/c0f02a84eb770db43a36ad35a4d59781.svg https://bkimg.cdn.bcebos.com/formula/0aeaee87a8b0305591c00a8f945eee9d.svg https://bkimg.cdn.bcebos.com/formula/0e9f5cd943d3c96f52f7845e1a85f0dd.svg Since carbonate can combine with protons in water to form bicarbonate and carbonic acid, and it can also combine with protons in acids to release carbon dioxide. Therefore, sodium carbonate is considered a Brønsted base in the acid-base proton theory. Reaction with acids: taking hydrochloric acid as an example. When there is an adequate amount of hydrochloric acid, sodium chloride and carbonic acid are formed; the unstable carbonic acid immediately decomposes into carbon dioxide and water. This reaction can be used to produce carbon dioxide: https://bkimg.cdn.bcebos.com/formula/5d4541a01fe99e062a664798e57de9d8.svg https://bkimg.cdn.bcebos.com/formula/4b7661d8ba55750d9492aad7a562757a.svg The overall chemical equation is: https://bkimg.cdn.bcebos.com/formula/a3b8f4bc92b9dba915a3ef588f6ddd84.svg When there is a small amount of hydrochloric acid, the following reaction occurs: https://bkimg.cdn.bcebos.com/formula/1d4e62d1ab3c95950a0342f16110b8c9.svg Sodium carbonate can also undergo similar reactions with other types of acids. Reaction with bases: Sodium carbonate can undergo double-displacement reactions with bases such as calcium hydroxide and barium hydroxide, producing precipitates and sodium hydroxide. This reaction is commonly used in industry to produce caustic soda (commonly known as the lye process): https://bkimg.cdn.bcebos.com/formula/4d866ec28fb13d24641cb1892ff82808.svg When it reacts with salts, sodium carbonate can undergo double displacement reactions with calcium salts, barium salts, etc., to produce precipitates and new sodium salts: https://bkimg.cdn.bcebos.com/formula/5cf5055383959e4e310fa55bce355b99.svg https://bkimg.cdn.bcebos.com/formula/15d7897b230c8d2a70c72d2f59e71850.svg Since sodium carbonate hydrolyzes in water to produce sodium hydroxide and carbonic acid, its reaction with certain salts shifts the chemical equilibrium in the desired direction, resulting in the formation of the corresponding base and carbon dioxide: https://bkimg.cdn.bcebos.com/formula/74d49d6dc877532dd9059205e2b03256.svg Soda is the transliteration of “Soda,” and its chemical formula is Na2CO3. It has many names; its scientific name is sodium carbonate. Besides being called soda, it is also known as soda ash or baking soda. Sodium carbonate with water of crystallization is called hydrated sodium carbonate. There are three types: sodium carbonate monohydrate (Na2CO3·H2O), sodium carbonate heptahydrate (Na2CO3·7H2O), and sodium carbonate decahydrate (Na2CO3·10H2O). Of the three types of soda, sodium carbonate has the widest range of uses. It is a very important chemical product, serving as a key raw material for industries such as glass manufacturing, soap production, textiles, papermaking, and leather processing. It is also used in the metallurgical industry and for water purification. It can also be used in the production of other sodium compounds. As early as the 18th century, it was listed alongside sulfuric acid, hydrochloric acid, nitric acid, and caustic soda as one of the basic chemical raw materials—the “three acids and two alkalis”. In daily life, soda has many uses as well; for example, it can be used directly as a detergent. Adding some soda when steaming buns helps to neutralize the acidic substances produced during the fermentation process. Baking soda https://bkimg.cdn.bcebos.com/pic/d043ad4bd11373f0f7f82d58a60f4bfbfaed0435?x-bce-process=image/resize,m_lfit,w_220,limit_1 Baking soda (sodium bicarbonate) has the chemical formula NaHCO3. It has many names as well; its scientific name is sodium bicarbonate, and it is also known as sodium hydrogen carbonate or acid sodium carbonate. Common names other than baking soda include burnt soda, fermented soda, and caustic soda. Baking soda is a white crystal that dissolves in water, and its aqueous solution is weakly alkaline. In hot air, it can decompose slowly, releasing some carbon dioxide ； When heated to 270°C, it decomposes completely, releasing carbon dioxide: https://bkimg.cdn.bcebos.com/formula/61a986c16a30e84fd039a1d25dabcb98.svg It can also react with acids (such as hydrochloric acid) to release carbon dioxide: https://bkimg.cdn.bcebos.com/formula/1f3a59c104c8332b4fb5c18b8f53a3e2.svg These properties of baking soda make it useful in many applications in industry and daily life. In fire extinguishers, it is one of the raw materials used to produce carbon dioxide ； In the food industry, it is a major raw material for baking powder ； It is also a commonly used ingredient in the production of cold drinks ； In medicine, it is a medication used to treat excess stomach acid. Sodium thiosulfate https://bkimg.cdn.bcebos.com/pic/a2cc7cd98d1001e93bc956c8ba0e7bec55e7977b?x-bce-process=image/resize,m_lfit,w_220,limit_1 Sodium thiosulfate is the common name for sodium thiosulfate; it is also known as hypo (a transliteration of the word “Hypo”). It contains five molecules of water of crystallization (Na2S2O3·5H2O), which is why it is also called sodium thiosulfate pentahydrate. Sodium carbonate is a colorless and transparent crystal that is soluble in water, and its aqueous solution is weakly alkaline. It weathers in dry air at temperatures above 33°C and loses its crystalline water. It is relatively stable in neutral and alkaline solutions, but decomposes rapidly in acidic solutions: https://bkimg.cdn.bcebos.com/formula/5925f204157c44b5d0456660806730e6.svg Baking soda has a strong chelating ability and can form complexes with silver bromide: https://bkimg.cdn.bcebos.com/formula/e08914b8ab86ad22db626c74c1cfcb35.svg Due to this property, it can be used as a fixing agent. During processing, excess baking soda reacts with the unexposed silver bromide on the film, converting it into a soluble substance https://bkimg.cdn.bcebos.com/formula/db98fe782af787**76d2d49f9500a4.svg, thereby removing AgBr and fixing the exposed areas. Baking soda also possesses strong reducing properties and can reduce substances such as chlorine: https://bkimg.cdn.bcebos.com/formula/1069b9d0ef66384b16ea69529c8e9c0b.svg Therefore, it can be used as a dechlorinating agent after bleaching cotton fabrics. By the same principle, iodine stains on fabrics can also be removed with it. Additionally, soda ash is also used in leather tanning, electroplating, and the extraction of silver from ores. Rotten soda – The above three are the three most common and frequently used types of “soda”. Apart from that, sometimes “stinky soda” is mentioned. https://bkimg.cdn.bcebos.com/pic/6a600c338744ebf8cb7729f8dbf9d72a6159a7f7?x-bce-process=image/resize,m_lfit,w_220,limit_1 Sodium sulfide is also known as ‘stinky soda’; its chemical formula is Na2S. It is also referred to as stinky alkali, yellow alkali, or sulfurized alkali, and it has a foul odor. Soluble in cold water, highly soluble in hot water, slightly soluble in alcohol. Industrial products are generally mixtures containing different amounts of crystal water, as well as various levels of impurities. Apart from differences in appearance and color, their density, melting point, boiling point, and other properties also vary due to the presence of these impurities. Sodium sulfide is an inorganic compound; pure sodium sulfide appears as a colorless crystalline powder. It has a strong tendency to absorb moisture and is soluble in water. The aqueous solution exhibits a strongly alkaline reaction. It can cause burns when it comes into contact with skin and hair. Therefore, sodium sulfide is commonly known as caustic sulfide. Sodium sulfide can explode when subjected to impact or rapid heating; it has unstable chemical properties and releases toxic hydrogen sulfide gas when in contact with acids: https://bkimg.cdn.bcebos.com/formula/9255bb5cbc8e7453d3741e74d87b7347.svg Sodium sulfide is used in the dye industry to produce sulfide dyes, and it serves as a raw material for cyanine sulfide and blue sulfide dyes. In the printing and dyeing industry, it is used as a dyeing aid for dissolving sulfur dyes. It is used in the tanning industry for hydrolysis to depile raw hides, and in the paper industry as a cooking agent for paper. It can also be used as a mordant in the dyeing of cotton fabrics in the textile industry, and in the pharmaceutical industry for the production of antipyretic drugs. Sodium sulfide can also be used in the treatment of conductive layers in direct electroplating; it reacts with palladium to form colloidal palladium sulfide, thereby enabling the formation of a good conductive layer on non-metallic surfaces. Key points of education for junior high school: At this level, students are generally expected to know the common names of sodium carbonate (such as soda ash and soda), its main uses, its chemical formula, as well as some common reactions. Examples can be found at: https://bkimg.cdn.bcebos.com/formula/5cf5055383959e4e310fa55bce355b99.svg https://bkimg.cdn.bcebos.com/formula/a3b8f4bc92b9dba915a3ef588f6ddd84.svg It is important to note that although sodium carbonate is commonly called soda ash, it is actually a type of salt. At the high school level, students are required to understand the differences between NaHCO3 and other substances in terms of their properties (solubility, thermal stability, strength of alkalinity, reaction rate with acids, etc.) and applications, as well as the methods for distinguishing between them. Among them, it is particularly important to understand the concepts of ionization and hydrolysis of strong-base weak acid salts represented by Na2CO3, as well as to calculate the ionization and hydrolysis equilibria. Main uses: Sodium carbonate is one of the important chemical raw materials. It is widely used in industries such as light industry and daily chemicals, building materials, the chemical industry, food industry, metallurgy, textiles, petroleum, national defense, and pharmaceuticals. It serves as a raw material for producing other chemicals, as well as a cleaning agent and detergent. It is also utilized in photography and analytical applications. Next are metallurgy, textiles, petroleum, defense, pharmaceuticals, and other industries. The glass industry is the largest consumer of soda ash, with 0.2 tons of soda ash consumed per ton of glass. In industrial soda ash, the main sectors are light industry, building materials, and the chemical industry, accounting for about 2/3; followed by metallurgy, textiles, petroleum, defense, pharmaceuticals, and other industries. 1. The glass industry is a major consumer of soda ash, with 0.2 tons of soda ash being used per ton of glass produced. It is mainly used in float glass, cathode ray tube glass envelopes, optical glass, etc. 2. It can also be used in other sectors such as chemicals and metallurgy. The use of heavy soda ash can reduce the dispersion of alkaline dust, lower raw material consumption, improve working conditions, and enhance product quality. It also reduces the erosion of refractory materials by alkaline powder, thereby extending the service life of kilns. 3. Used as a buffer, neutralizer, and dough improver; it can be applied to pastries and baked goods in appropriate amounts according to production needs. 4. Used as a detergent for rinsing wool, in bath salts and pharmaceuticals, as an alkali in tanning. 5. Used in the food industry as a neutralizing agent and leavening agent, for example in the production of amino acids, soy sauce, and baked goods such as steamed buns and bread. It can also be turned into an alkaline solution and added to pasta to increase its elasticity and ductility. Sodium carbonate can also be used in the production of monosodium glutamate, as reagents specific for color televisions, and in the pharmaceutical industry as an antacid and a osmotic laxative. 8. Anhydrous sodium carbonate is used for chemical and electrochemical degreasing, electroless copper plating, etching of aluminum, electrolytic polishing of aluminum and its alloys, chemical oxidation of aluminum, sealing after phosphating, rust prevention between processing steps, electrolytic removal of chromium platings and chromium oxide films, etc. It is also used in electrolytes for pre-copper plating, steel plating, and steel-alloy plating. 9. In the metallurgical industry, it is used as a flux in smelting, as a flotation agent in mineral processing, and as a desulfurizing agent in steel and antimony production. 10. Used as a water softener in the printing and dyeing industry. 11. The tanning industry uses it for degreasing raw hides, neutralizing chromium-tanned hides, and increasing the alkalinity of chromium tanning solutions. 12. Quantitative analysis uses the standardized acid solution as a benchmark. Aluminum, sulfur, copper, lead, and zinc are determined. Test urine and whole blood glucose. Analysis of solubilizers for silica in cement. Metallographic analysis, etc.; production technologies; laboratory methods; laboratory preparation of sodium carbonate: https://bkimg.cdn.bcebos.com/formula/cf5878dd4b56d4057049842b9f6eec32.svg. The Leblanc process was first used in 1791; ancient people began producing sodium carbonate using salt, sulfuric acid, coal, and limestone as raw materials – this is the Leblanc process. This method suffers from inadequate utilization of raw materials, poor working conditions, and low product quality, and was gradually replaced by the Solvay process. The Solvay process: In 1859, the Belgian chemist Solvay used table salt, ammonia, and carbon dioxide as raw materials to precipitate sodium bicarbonate from a solution at room temperature; heating this substance then led to its decomposition into sodium carbonate. This method was named the Solvay process, and it has been in use to this day. The first step involves the reaction of ammonia with water and carbon dioxide to form one molecule of ammonium bicarbonate: https://bkimg.cdn.bcebos.com/formula/e025eadd188e92ce615ed16487928c65.svg The second step is the reaction of ammonium bicarbonate with sodium chloride, resulting in the formation of sodium bicarbonate precipitate and ammonium chloride. Sodium bicarbonate precipitates because it has low solubility. After filtration, solid sodium bicarbonate is obtained: https://bkimg.cdn.bcebos.com/formula/f213aeb2f217ea99cf40872440e41362.svg The overall chemical equation for these two steps is: https://bkimg.cdn.bcebos.com/formula/c2b408fe4d840f6d6cc48cbf60c31ec1.svg Step three involves heating sodium bicarbonate to cause it to decompose, producing water, carbon dioxide, and sodium carbonate – which is the soda ash we are after: https://bkimg.cdn.bcebos.com/formula/32ce78975d8f64de736ea4bf75064eca.svg Step four entails mixing the ammonium chloride produced as a by-product in step two with slaked lime and heating them; the ammonia gas generated can be reused: https://bkimg.cdn.bcebos.com/formula/461b04079746b6eeed57712c0de27f39.svg The Hou process for soda production was developed in 1943 when Chinese scientist Hou Debang returned from studying abroad. Taking into account China’s shortage of salt resources, he improved upon the Solvay process by combining the production of soda ash and synthetic ammonia, thereby enabling the simultaneous manufacture of both sodium carbonate and the fertilizer ammonium chloride. This approach significantly increased the efficiency of salt utilization; this is what is known as the Hou process for soda production. In the first step, ammonia reacts with water and carbon dioxide to form one molecule of ammonium bicarbonate. In the second step, ammonium bicarbonate reacts with sodium chloride, resulting in the formation of sodium bicarbonate precipitate and ammonium chloride. Sodium bicarbonate precipitates because its solubility is low. Sodium bicarbonate solid is obtained after filtration. (These two steps are the same as those in the Solvay process mentioned above). https://bkimg.cdn.bcebos.com/pic/a2cc7cd98d1001e9122d6fc8ba0e7bec55e797e7?x-bce-process=image/resize,m_lfit,w_220,limit_1 Step 3 of the Hou’s method for producing soda ash: The sodium bicarbonate that is synthesized can be sold directly. The remaining sodium bicarbonate is heated and decomposed to produce sodium carbonate, while the carbon dioxide generated can be reused in Step 1. Based on the principle that NH4Cl has a higher solubility than NaCl but a lower solubility than NaCl at low temperatures, fine table salt powder is added to the mother liquor at 278K–283K (5 ℃–10 ℃), causing NH4Cl to crystallize out separately for use as a nitrogen fertilizer. The difference between the Solvay process and the Hall-Héroult process is that in the Solvay process, NH3 is recycled throughout the production process, whereas in the Hall-Héroult process, CO2 is recycled, with NH4Cl serving directly as a by-product of soda ash – namely, a fertilizer. Therefore, the product of the Solvay process is sodium carbonate, with calcium chloride as a by-product ； The product of the Hou method is sodium carbonate, with ammonium chloride as a by-product. Advantages of this method: it retains the advantages of the ammonia-alkali method while eliminating its disadvantages, increasing the utilization rate of table salt to 96% ； NH4Cl can be used as a nitrogen fertilizer ； It can be combined with ammonia synthesis plants to convert the CO in the raw material gas for ammonia synthesis into CO2, eliminating the need for the process of producing CO2 from CaCO3. Technical specifications: Parameter | Category 1 | Category 2 | Category 3 | Total alkali content (%): 99 | 98 | 96; Chlorides (%): 0.5 | 0.9 | 1.2; Water-insoluble substances (%): 0.04 | 0.1 | 0.15; Iron (%): 0.004 | 0.006 | 0.010; Sulfates (%): 0.03 | 0.08 | –; Loss on ignition (%): 0.8 | 1.0 | 1.3. Safety considerations: Health hazards – This product has mild irritant and mild corrosive properties. Direct contact can cause skin and eye burns. Inhalation of its dust and fumes during production can cause respiratory irritation and conjunctivitis, as well as ulcers and atrophy of the nasal mucosa and perforations of the nasal septum. Prolonged exposure to this solution can cause eczema, dermatitis, callus-like ulcers, and skin laxity. The incidence of respiratory diseases among workers exposed to this product is increasing. Accidental ingestion can cause burns to the digestive tract, mucosal erosion, bleeding, and shock. Usage instructions: Wear appropriate protective clothing and gloves. If it comes into contact with the eyes accidentally, rinse immediately with plenty of water and consult a doctor. Do not inhale dust. Wear appropriate protective clothing. Wear goggles or a mask. Ingestion is harmful. Irritates the eyes. Toxic to aquatic organisms, and may have long-term adverse effects on the aquatic environment. Irritates the eyes, respiratory system, and skin. Irritates the respiratory system and skin. Causes severe damage to the eyes. Toxicological data: LD50: 4090 mg/kg (oral, rats); LC50: 2300 mg/m3 over 2 hours (inhalation, rats). Flammability and explosivity: This substance is not flammable, but it is corrosive and irritating. First aid measures: In case of skin contact, remove the contaminated clothing immediately and rinse the affected area with plenty of flowing water for at least 15 minutes. Seek medical attention. (In experiments, when alkali solution gets on the skin by accident, we need to rinse it off with plenty of water, and then apply boric acid solution to neutralize it.) Eye contact: Immediately lift the eyelids and rinse the eyes thoroughly with copious amounts of running water or saline for at least 15 minutes. Seek medical attention. Inhalation: Move to a place with fresh air away from the scene. In case of difficulty breathing, administer oxygen. Seek medical attention. Ingestion: Rinse the mouth with water and give milk or egg white to drink. Seek medical attention. Fire-fighting measures: Hazardous characteristic: Corrosive. It has no special combustion or explosion properties. Harmful combustion products: Natural decomposition products are unknown. Fire extinguishing method: Firefighters must wear full-body acid- and alkali-resistant firefighting suits. When extinguishing a fire, move the container away from the fire site to an open area as much as possible. Emergency response to leaks: Isolate the area contaminated by the leak and restrict access. It is recommended that emergency responders wear dust masks (full-face masks) and protective clothing. Avoid dust; sweep carefully, place it in a bag, and transfer it to a safe location. In the event of a large leak, cover it with plastic sheeting or canvas. Collect and recycle, or transport to waste disposal sites for disposal. Precautions: Operate in a sealed environment and ensure adequate ventilation. Operators must receive specialized training and strictly adhere to operating procedures. It is recommended that operators wear self-priming filter dust masks, chemical safety goggles, protective clothing resistant to toxic substances, and rubber gloves. Avoid generating dust. Avoid contact with acids. Handle with care during transportation to prevent damage to the packaging and containers. Equipped with leak emergency response equipment. Empty containers may retain harmful substances. When diluting or preparing solutions, the base should be added to water to avoid boiling and splashing. Storage precautions: Store in a cool, well-ventilated warehouse. Keep away from flames and heat sources. It should be stored separately from acids and similar substances; mixed storage must be avoided. The storage area should be equipped with suitable materials to contain leaks. 【Prohibited substances】Strong acids, aluminum, fluorine. Shipping precautions: The packaging must be intact at the time of shipment, and the loading must be done carefully. During transportation, it is necessary to ensure that the container does not leak, collapse, fall, or get damaged. Mixing or transporting it together with acids, food chemicals, etc. is strictly prohibited. During transportation, it should be protected from exposure to sunlight and rain, as well as high temperatures. The vehicle should be thoroughly cleaned after transportation is completed. Additional relevant materials and supplementary content to be added; contributor of this content to be added