THE REFINING OF SEA SALT 



29 



The shape, size, and physical characteristics of salt crystals are controlled in 

 practice by the manipulation of the brine during crystallization and by the methods 

 employed in draining, kiln-drying, and screening the crystallized product. Proper 

 manipxdation is accomplished by the control of the brine temperature during 

 crystallization, by the amount of mechanical stirring or agitation of the brine, and 



{Courtesy Leslie Salt Co.) 



Fig. 3-1. Modern plant of the Leslie Salt Co. at Newark, California, where 

 salt is produced by solar evaporation and tlien refined for domestic and 

 industrial use. 



by the length of time the newly formed crystals are allowed to remain in the brine 

 after sinking and before removal. 



The grains in the marketed product are only approximately the shape of those 

 produced in evaporation experiments because the subsequent handling of the 

 crystals in the refinery by centrifuging, storing in warehouse, steam-drying in 

 rotary kilns, screening to size, etc., breaks the crystals and eflFectually changes 

 their original appearance. Nevertheless, the nature of the final product, whether 

 coarse grained or fine grained, flaky like filaments resembling mica or cubical like 

 minute dice, depends upon how the brine is evaporated. 



The brine in vacuum pans boils violently, and the salt thus produced consists of 

 very small cubical crystals. The particles are smooth and slightly rounded at the 

 corners and edges. When thoroughly dry and screened between certain size limits, 

 vacuum-pan salt pours and sifts readily. 



The so-called Enghsh flash grainer system operates by first raising the tempera- 

 ture of the brine considerably above its boiling point in a closed heater and by 

 spurting the superheated brine into a drum, or chamber, where it separates 



