pH value of soda ash

Generally speaking, the pH value of sodium carbonate solution will be above 10. When fully dissolved, it will be around 11.6 and will not exceed 12.

Generally, when the concentration of strong acid and strong alkali is lower than 1 mol/L, it is expressed by pH value. When the concentration is higher than 1 mols/L, it cannot be expressed by pH value. I don’t know, right?

do an experiment: Just dissolve some sodium carbonate and check it with a pH meter.

It is related to the concentration and temperature of the solution. Without the limitations of concentration and temperature, it seems meaningless to talk about the PH value of the soda ash solution. If your concentration is close to saturation, it is not recommended to use an indicator such as pH value to measure it. Only in dilute solutions does pH have any meaning. This is how I understand it: If the concentration is too high, the theory that the concentration product of hydrogen ions and hydroxyl radicals equals ten to the negative fourteenth power does not seem to exist, so we cannot talk about the concept of pH value, right?

I don’t know if the poster is talking about soda ash, sodium carbonate, or all alkali. For all bases, the highest pH is 1. If the concentration exceeds 1 mol/l, it cannot be expressed by ph.

Sodium carbonate, Chinese synonyms: edible soda ash; soda; soda; anhydrous sodium carbonate; soda water; sodium carbonate; alkali powder. Melting point 851 °C (lit.) Boiling point 1600°C Density 2.53 Refractive index 1.535 Storage conditions 2-8°C Solubility H2O: 1 M at 20 °C, clear, colorless Water solubility 22 g/100 mL (20 ºC) Sensitivity Hygroscopic Merck 14,8596 The chemical formula of sodium carbonate is Na2CO3. It is commonly known as soda ash, soda, soda ash, and washing soda. It is usually a white powder and is a strong electrolyte. The density is 2.532g/cm3, the melting point is 851°C, it is easily soluble in water, and has the properties of salt. It is a weak acid salt, slightly soluble in anhydrous ethanol, and insoluble in propanol. After being dissolved in water, a hydrolysis reaction occurs, making the solution alkaline and somewhat corrosive. It can neutralize with acids to generate corresponding salts and release carbon dioxide. It can decompose at high temperatures to produce sodium oxide and carbon dioxide. Long-term exposure to the air can absorb moisture and carbon dioxide in the air, generate sodium bicarbonate, and form hard lumps. It is highly hygroscopic, easily forms into hard lumps, and does not decompose at high temperatures. Sodium carbonate and water generate three hydrates: Na2CO3·10H2O, Na2CO3·7H2O, and Na2CO3·H2O. Among them, Na2CO3·10H2O is the most stable, and the heat of dissolution when dissolved in water is very small. It is mostly used in the photography industry, and its trade name is carbon oxygen. Na2CO3·10H2O, also known as crystalline alkali, is easily weathered in dry air. In the past, crystalline alkali was often used for home washing and wool washing, so it was also called "washing soda". In the past, our country’s folk * It is customary to use "block alkali" that can be used for both washing and baking. It is made by stirring soda ash with a large amount of water (plus some baking soda (NaHCO3)), and its water content is more than 50%. Sodium carbonate exhibits an endothermic reaction when dissolved in water and is easily weathered in the air. Na2CO3·7H2O is unstable and can only precipitate from the saturated solution of sodium carbonate in the range of 32.5 to 36°C. Sodium carbonate is a weak acid and strong base salt (soda ash is a salt, not a base, but the solution is strongly alkaline). Na2CO3 produced by chemical methods is purer than natural alkali, so people call it "soda ash". Maximum dissolved grams per 100 grams of water at different temperatures (℃): 7.0g/0℃; 12.2g/10℃; 21.8g/20℃; 29.4g/25℃; 39.7g/30℃; 48.8g/40℃;47.3g/50℃;46.4g/60℃;46.2g/70℃;45.8g/80℃; 45.7g/90℃;45.5g/100℃; The industrial preparation method uses ammonia, carbon dioxide and saturated salt water as raw materials. It is called the combined alkali production method. It was improved by the Chinese chemist Hou Debang on the basis of the ammonia-alkali method. This method won a gold medal at the World Expo. In North America, due to the existence of large amounts of natural sodium carbonate deposits, artificial processing and refining of natural alkali is the main means of producing sodium carbonate. Sodium carbonate is an important raw material in chemistry and industry. In 2003, China's sodium carbonate production surpassed the United States and ranked first in the world. Before the invention of the combined alkali production method, the ammonia-alkali method (also known as the Solvay alkali production method) was the most widely used. It was invented by Belgian Ernest Solvay in 1862. The reaction proceeds in three steps: 1.NH3 + CO2 + H2O → NH4HCO3 2.NH4HCO3 + NaCl → NaHCO3 + NH4Cl 3.2NaHCO3 → Na2CO3 + CO2 + H2O The CO2 generated by the reaction can be recycled and reused, and NH4Cl can react with quicklime to produce NH3, which can be reused as raw material.: 2NH4Cl + CaO → 2NH3 + CaCl2 + H2O The ammonia-alkali method enables continuous production, improves the utilization rate of salt, and the product quality is pure, so it is called "soda ash", but the biggest advantage is its low cost. In 1867, the products manufactured by Solvay set up a factory and won a bronze medal at the Paris World's Fair. This method was officially named the Solvay method. At this time, the price of soda ash * * decline. The news reached the United Kingdom, and the British Hutchinson Company, which was engaged in the production of alkali using the Rublan process, obtained the exclusive rights to the Solvay process for two years. In 1873, the Hutchinson Company was reorganized into the Bruneimen Company and established a large-scale factory for the production of soda ash. Later, France, Germany, the United States and other countries successively built factories. These * * Initiated the organization Solvay Guild. The design drawings are only disclosed to member states and are strictly kept secret from the outside world. Whenever improvements or new discoveries are made, member states communicate with each other and agree not to apply for patents to prevent leakage. In addition to technology, there are also business restrictions. They adopt a regional sales approach. For example, the Chinese market is exclusively owned by the British company Benedictine. Due to such a strict organizational method, anyone who does not obtain the franchise from the Solvay Guild has no way of knowing the details of ammonia-alkali production. Until the early 20th century, many * * Manufacturers who want to explore the secrets of Solvay always end up in failure. It was not until the relevant patent expired that this production method was revealed to the world. The difference between Hou's and Sox's methods: Mainly reflected in the attitude towards ammonium chloride. Soxhlet added quicklime to cause ammonia to escape, while Houthlet added salt to crystallize ammonium chloride. The production methods of soda ash include ammonia-alkali method, combined alkali method, trona processing, etc. The main reactions of the ammonia-alkali method are as follows: NaCl+NH3+CO2+H2O→NaHCO3+NH4Cl 2NaHCO3→Na2CO3+CO2+H2O The process flow is briefly described as follows: The raw salt is dissolved in water, and calcium and magnesium are removed to make refined brine (or secondary brine, the same below). The secondary brine absorbs ammonia to produce ammonia salt water with a NaCl concentration above 89 titers and a ratio of FNH3 to Na+ concentration of 1.13 to 1.18. The oxygen brine is cooled to 35-38°C and then sent to the carbonization section. It reacts with the compressed carbon dioxide from the lime kiln and calciner to generate a sodium bicarbonate suspension, which flows to the filtration section. The sodium bicarbonate (heavy alkali) crystals are separated from the suspension and sent to the upper calcination section, where they are calcined and decomposed at about 160°C to produce soda ash products. The filtered mother liquor is mixed with the lime milk from the lime section to make a blended liquid, and the ammonia in it is heated with steam in the distillation tower and used for the brine to absorb ammonia for recycling. The production process of the combined alkali production method is divided into an alkali production process (also called the I process) and an ammonium production process (also called the II process). Soda ash and ammonium chloride are co-produced, and the mother liquor forms a closed cycle in the two processes. The main reaction is the same as the ammonia-alkali method. The process flow is briefly described as follows: The raw salt (sodium chloride) is washed with saturated brine to remove calcium and magnesium impurities, and then crushed, washed, thickened, and separated to obtain washed salt that meets the specified purity (containing NaCl ≥ 98%) and particle size (10 to 20 mesh), and sends it to the salting out crystallizer. The mother liquor II overflowing from the salting out crystallizer absorbs ammonia in the ammonia absorber to produce ammonia mother liquor II. After clarification, it is sent to the carbonization tower to absorb carbon dioxide (carbonization) to produce a sodium bicarbonate suspension. The sodium bicarbonate suspension is filtered to obtain solid sodium bicarbonate, which is then calcined to obtain a soda ash product. The mother liquor (Mother liquor I) after filtering the heavy alkali is made into ammonia mother liquor I by absorbing ammonia. It exchanges heat with the mother liquor II through a heat exchanger. After cooling, it is sent to the refrigeration crystallizer. It directly conducts heat exchange with the cooling medium (brine) or the refrigerant (liquid ammonia) through the external cooler, and is cooled at 5 to 10°C to precipitate part of the ammonium chloride. The overflow liquid of the cold crystallizer (semi-mother liquor II) flows into the salting crystallizer, and washing salt is added to precipitate part of the ammonium chloride. The ammonium chloride suspension taken out from the cold precipitation and salting out crystallizer is thickened and separated to obtain wet ammonium chloride, which is sent to a dry ammonium furnace for drying to become the ammonium chloride product. The salting-out crystallizer overflow (mother liquor II) exchanges heat with the ammonia mother liquor L and absorbs ammonia to produce ammonia mother liquor II, which is then sent to the carbonization tower for alkali production. In this continuous cycle, two products, soda ash and ammonium chloride, are continuously produced. Trona Processing Method Sesquite Process This method is a method of producing soda ash using sesquite as raw material. Used by some trona processing plants in the United States. The ore is crushed to about 20 mesh (O.8mm), sent to the dissolving tank, dissolved with circulating mother liquor to make a saturated solution, and then enters the clarification barrel for clarification. The bottom flow is sent to the thickener, and washed with water to recover the alkali content in the mud. The overflow liquid of the clarification barrel is filtered and sent to the three-effect evaporator for evaporation. The crystal slurry taken out from the third-effect evaporator is pumped to the thickener, and then centrifuged and dehydrated to obtain sodium sesquicarbonate filter cake, which is then calcined to produce soda ash. The carbon monohydrate process is also a method for producing soda ash using sesquibase as raw material. Its product quality is better than the sesquibase process and is used by most trona processing plants in the United States. The ore is crushed to about 6 mm, sent to the calcining furnace, and calcined at about 150°C. Most of the ore is crude soda ash, which enters the dissolving tank and is dissolved at slightly lower than 100°C. After clarification, it is sent to a three-effect evaporator. The evaporated and concentrated suspended alkali liquid is separated to obtain sodium carbonate monohydrate, which is sent to a dryer for drying to obtain heavy soda ash. Carbonation method This method is a production method using trona halogen as raw material, and is used in trona processing in Dabusu and other places in my country. The alkali brine extracted from trona or dissolved in water is clarified, preheated, and carbonated with carbon dioxide, and then filtered and calcined to obtain soda ash products. In the mid-1980s, the ammoniation and carbonization method was successfully developed, in which the refined alkali halide absorbs nitrogen first and then carbonizes it. The subsequent steps are the same as before. Compared with the direct carbonization method, the sodium utilization rate of the ammonia carbonization method can be increased from 25% to 65% to 70%. The trona brine evaporation method uses solution mining of trona ore or trona excavated from alkali lakes to prepare alkali brine. After refining, separation, preheating, evaporation, separation and calcination, high-quality soda ash is obtained. In soda ash production, the concentration of soda ash in ammonia-alkali method and combined alkali method is generally expressed by titer (one-twentieth equivalent concentration). In trona production, the concentration is generally expressed in grams/liter. In soda ash production, pH value is rarely used to describe its concentration. Alkali corrosion is rarely considered in the production of ammonia-alkali method and combined alkali method, because both ammonia and chlorine in the system are more corrosive than soda ash. Therefore, the selection of materials in production is generally based on ammonia or chlorine. Carbon steel is generally used in trona production. For example, in the production of hot soda hydroxide, titanium is generally used during evaporation and concentration due to its high chloride content. In the soda ash calcination process, corrosion at high temperatures is generally considered, and high-quality low-carbon alloy steel is selected as the material. I wonder if the poster is considering the corrosion of the equipment when considering the PH value? If the corrosion rate of a pure sodium carbonate solution at a normal temperature is higher and the concentration is higher, the corrosion rate will not be too great. Just consider the corrosion allowance of carbon steel appropriately. Personal opinion, for reference only.

Can ordinary Q235 carbon steel be used to make containers for Na2CO3 solution?