SALT FROM SEA WATER 



23 



the rate of evaporation also aflFect the size of the crystals. Cold weather causes the 

 formation of small hard crystals. Hot weather and a low brine stratum during 

 crystallization result in the formation of soft crystals. 



As more and more of the salt crystallizes from the solution the magnesium and 

 calcium chloride content of the mother liquor increases; this causes the mother 



(.Courtesy Leslie Salt Co.) 



Fig. 2-2. In California, solar evaporation ponds are flooded by a system of canals. 

 The system is so arranged that salt water can be diverted to any ponds requiring re- 

 filling to replace evaporation. 



liquor to become oily in appearance. The greater proportion of the salt crystallizes 

 from the solution between the densities 1.2185 sp. gr. (26° Be.) and 1.2341 sp. gr. 

 (27.5° Be.). 



It requires some skill to regulate the requirements of the crystallizing ponds so 

 that there will always be enough saturated brine on hand from the last concentra- 

 tion ponds ( pickling ponds ) . If there is an oversupply the mother liquor is drawn 

 off at 1.2394 sp. gr, (28° Be.). Otherwise, the brine is allowed to remain in the 

 crystallization ponds until it reaches a density of 1.2500 sp. gr. (29° Be.) as some 

 salt continues to crystallize. If the brine is permitted to evaporate at higher 

 densities, the salt which crystallizes becomes more and more impure and a film 

 of salt begins to cover the greater part of the pond. The mother liquor which is 

 drawn off from the crystallizers is called bittern. The salt manufacturers utilize 

 the bittern for making various by-products; these processes are described in 

 Chapter 4. 



The crystallization ponds are filled from two to five times each season. The 

 brine is run in on the previous crystallizations for the salt is not harvested until 

 the end of the season. In this region the salt is removed from the crystallizers 

 before the December rains begin. 



