Ordinary soaps are sodium salts of higher fatty acids and are generally made by saponification of fats and oils in the presence of a slight excess of caustic soda.
If fatty acids are used directly as raw materials, soda ash can also be used instead of caustic soda to make soap.
Printing and dyeing, textile industry, but also with a large amount of lye to remove the cotton yarn, wool and other oils and fats on it. The production of man-made fibers also need caustic soda or soda ash. For example, the production of viscose fiber first 18-20% caustic soda solution (or soda solution) to impregnate cellulose, so that it becomes alkali cellulose, and then the alkali cellulose drying, crushing, and then added to the disulfide
Finally, with a dilute lye to dissolve the sulfonate, it will be obtained by the viscose liquid. Then after filtering and vacuuming (to remove air bubbles), it can be used to draw silk.
Caustic soda is also used to refine petroleum. In order to remove the gum in the petroleum fraction, generally in the petroleum fraction with concentrated sulfuric acid in order to make the gum become acid residue and precipitation. After acid washing, the petroleum also contains phenol, naphthenic acid and other acidic impurities, as well as excess sulfuric acid, which must be washed with caustic soda solution, and then washed with water in order to obtain refined petroleum products.
In the paper industry, the first step is to use chemical treatment, the raw materials containing cellulose (such as wood) and chemicals steamed to make pulp. The so-called alkaline pulping is the use of caustic soda or soda ash solution as a cooking solution to remove lignin, carbohydrates and resins from the raw material and neutralize the organic acids in it, so that the cellulose is separated out.
In the metallurgical industry, it is often necessary to convert the active ingredients in the ore into soluble sodium salts in order to remove the insoluble impurities, therefore, it is often necessary to add soda ash (which is also a flux), and sometimes caustic soda. For example, in the smelting process of aluminum, used in the preparation of cryolite and bauxite treatment, are to use soda ash and caustic soda. Another example is the smelting of tungsten, but also the first concentrate and soda ash roasted into soluble sodium tungstate, and then by acid precipitation, dehydration, reduction and other processes to produce powdered tungsten.
In the chemical industry, the system of sodium metal, electrolysis of water are used caustic soda. The production of many inorganic salts, especially the preparation of some sodium salts (such as borax, sodium silicate, sodium phosphate, sodium dichromate, sodium sulfite, etc.) are to use caustic soda or soda ash. Synthetic dyes, drugs and organic intermediates, etc. also need to use caustic soda or soda ash.
In addition, soda ash is also used in the food industry and daily life.