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Salt (sodium chloride) has been a valuable commodity since prehistoric times, and its extraction from seawater also goes back to prehistory. Salt is extracted from seawater in many countries around the world, but the majority of salt put on the market today is mined from solid evaporite deposits.
The ancient Chinese gradually mastered and advanced the techniques of producing salt. Salt mining was an arduous task for them, as they faced geographical and technological constraints. Salt was extracted mainly from the sea, and salt works in the coastal areas in late imperial China equated to more than 80 percent of national production. [5]
The only major inputs to the Solvay process are salt, limestone and thermal energy, and its only major byproduct is calcium chloride, which is sometimes sold as road salt. After the invention of the Haber and other new ammonia-producing processes in the 1910s and 1920s its price dropped, and there was less need in reclaiming it.
Open-pan salt production was confined to a few locations where geological conditions preserved layers of salt beneath the ground. Only five complexes of inland open-pan salt works now survive in the world: Lion Salt Works, Cheshire, United Kingdom; Royal Saltworks at Arc-et-Senans, Salins-les-Bains, France; [6] Saline Luisenhall, Göttingen, Germany; [7] the Salinas da Fonte da Bica, Rio Maior ...
A salt evaporation pond is a shallow artificial salt pan designed to extract salts from sea water or other brines. The salt pans are shallow and expansive, allowing sunlight to penetrate and reach the seawater. Natural salt pans are formed through geologic processes, where evaporating water leaves behind salt deposits.
Acid–base extraction is a subclass of liquid–liquid extractions and involves the separation of chemical species from other acidic or basic compounds. [1] It is typically performed during the work-up step following a chemical synthesis to purify crude compounds [ 2 ] and results in the product being largely free of acidic or basic impurities.
Typically aqueous sodium hydroxide solutions are used. [1] [2] It is an important type of alkaline hydrolysis. When the carboxylate is long chain, its salt is called a soap. The saponification of ethyl acetate gives sodium acetate and ethanol: C 2 H 5 O 2 CCH 3 + NaOH → C 2 H 5 OH + NaO 2 CCH 3
The sodium–mercury amalgam flows to the center cell, where it reacts with water to produce sodium hydroxide and regenerate the mercury. Mercury cell electrolysis, also known as the Castner–Kellner process , was the first method used at the end of the nineteenth century to produce chlorine on an industrial scale.