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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 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.
Sodium chloride (NaCl) melts at 801 °C (1074 Kelvin), but a salt mixture can be kept liquid at a temperature as low as 600 °C at the mixture containing, by weight: 33.2% NaCl and 66.8% CaCl 2. If pure sodium chloride is used, a metallic sodium emulsion is formed in the molten NaCl which is impossible to separate.
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]
Diagram of Castner process apparatus. The Castner process is a process for manufacturing sodium metal by electrolysis of molten sodium hydroxide at approximately 330 °C. Below that temperature, the melt would solidify; above that temperature, the molten sodium would start to dissolve in the melt.
From cold solutions, salt crystallises as the dihydrate NaCl·2H 2 O. Solutions of sodium chloride have very different properties from those of pure water; the freezing point is −21.12 °C (−6.02 °F) for 23.31 wt% of salt, and the boiling point of saturated salt solution is around 108.7 °C (227.7 °F).
The company dates back to 1913, when five California businessmen staked $100 apiece (about $3,000 today) to build a factory making bleach out of salt extracted from San Francisco Bay.
Sodium was first isolated by Humphry Davy in 1807 by the electrolysis of sodium hydroxide. Among many other useful sodium compounds, sodium hydroxide is used in soap manufacture, and sodium chloride (edible salt) is a de-icing agent and a nutrient for animals including humans. Sodium is an essential element for all