Concept of soda ash
1. Soda soda, also known as soda, alkali ash, alkaline noodles or washing alkali, consists of sodium carbonate, with molecular formula of Na2CO3 and molecular weight of 105.99.
2. Sodium carbonate is white and odorless powder or particles at room temperature, which has water absorption. When exposed to the air, it will gradually absorb water and form a lump. Sodium carbonate is easily soluble in water and glycerol, and slightly soluble in anhydrous ethanol. The solubility is the highest at 35.4℃, and 49.7 grams of sodium carbonate can be dissolved in 100 grams of water.
3. Sodium carbonate is a sodium salt, which ionizes in aqueous solution to generate hydroxide ions, and the aqueous solution is alkaline (pH= 1 1.6). Sodium carbonate is corrosive and stable, but it can also be decomposed into sodium oxide and carbon dioxide at high temperature. Long-term exposure to the air will absorb water and carbon dioxide and generate sodium bicarbonate (baking soda).
4. Sodium carbonate can react with acid, salt and alkali respectively: it can react with acid through double decomposition. In the case of sufficient hydrochloric acid, sodium chloride and carbonic acid will be generated, unstable carbonic acid will be immediately decomposed into carbon dioxide and water, and sodium carbonate can also react with other kinds of acids. It can undergo metathesis reaction with salt, for example, some calcium salts and barium salts can form precipitation and new sodium salts with sodium carbonate; It can react with alkali such as calcium hydroxide and barium hydroxide to generate precipitation and sodium hydroxide, which will be used to prepare caustic soda (sodium hydroxide) in industry, commonly known as causticization.
Classification of soda ash
1. According to different densities, soda ash is mainly divided into light soda ash (abbreviated as light soda ash) and heavy soda ash (abbreviated as heavy soda ash). Both of them are sodium carbonate in chemical composition, but their physical forms are different: light soda ash is white crystalline powder with a density of 500- 600kg/m_; The density of heavy alkali is 1000- 1200kg/m_, showing white fine particles. Compared with light alkali, heavy alkali has the characteristics of firmness, large particles, high density, low hygroscopicity, difficulty in caking, flying and good fluidity. In addition, there are ultra-light soda ash and ultra-heavy soda ash with densities of about 370kg/m_ and 1550-2553kg/m_, respectively.
2. Soda can be divided into industrial soda and edible soda according to different uses. Industrial soda ash shall conform to GB/T 2 10- 2004 "Industrial Sodium Carbonate and Its Test Methods" (hereinafter referred to as the national standard), and edible soda ash shall conform to GB 1886-1992 "Sodium Carbonate as a Food Additive". On the basis of reaching the low salinity standard of industrial soda ash, the content limits of arsenic and heavy metals are increased.
3. According to the different chloride content, soda ash can be divided into ordinary alkali, low salt, ultra-low salt and ultra-low salt. Mass fraction of common alkaline sodium chloride ≤1.20%; The mass fraction of low salinity sodium chloride is less than or equal to 0.90%; The mass fraction of ultra-low saline-alkali sodium chloride is less than or equal to 0.70%; The mass fraction of ultra-low salt sodium chloride is less than or equal to 0.30%.