CHAPTER 3 

 The Refining of Sea Salt 



The Necessity of Refining Sea Salt 



Regardless of the process used in making solar sea salt the crude product con- 

 tains more or less insoluble mineral and organic matter, chiefly scraped up from 

 the floor of the saline, an appreciable amount of calcium and magnesium chlorides, 

 sulfates, and many microorganisms. 



Sodium chloride has a brackish, but not bitter, taste, whereas, calcium and 

 magnesiimi salts are very bitter. Consequently, the higher the content of calcium 

 and magnesium salts in common salt, the more bitter its taste. Iron, organic matter, 

 and bacteria, usually found in crude solar salt, cause it to be colored. Some sea 

 salt contains relatively high numbers of red bacteria which often give it a pink 

 tinge. Organic matter of marine origin give sea salts peculiar odors, often described 

 as the "smell of the sea." Although pure sodium chloride is only very slightly hygro- 

 scopic, calcium and magnesium chlorides absorb moisture readily; therefore, the 

 presence of even small amounts of these salts is sufficient to make sea salt hygro- 

 scopic. 



For many purposes, such as table, dairy, and chemical, nearly pure salt is re- 

 quired. The demand for pure salt causes it to bring a higher price than crude 

 salt. Since it is difficult to produce high grade salt by the solar process, the most 

 modern salt works, desiring to market their salt in the most valuable form, refine 

 the low grade salt by various processes, which will be considered in this chapter. 



Little sea salt is refined in Europe since most of the refineries are located in 

 Great Britain, Austria, and Germany, where the salt is obtained either from 

 mines or wells. 



The American sea-salt refining industry is located in the vicinity of San Francisco 

 Bay, California, the center of the solar sea-salt industry. Four salt works operate 

 very large refineries in that locality. 



The composition of the solar sea salts from various parts of the world is given 

 in Table 6 on page 15. 



American Processes of Refining Sea Salt 



Principles and Methods. Sea salt is refined either by rewashing, grinding, and 

 screening the crude product, or by dissolving and recrystallizing it in grainers or 

 vacuum pans. 



A clear understanding of the mechanical principles of salt-crystal formation is 

 necessary for a scientific study of salt refining. Salt crystals have their beginning 

 as vapor rises from heated brine and tiny specks begin to appear at the surface. 

 The individual "seed crystals" enlarge rapidly, the rate of growth depending upon 

 the rate of heat supplied and subsequent evaporation. If undisturbed, the salt 



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