THE REFINING OF SEA SALT S6 



tion, accomplished either by overheating the underlying metal to loosen the scale 

 or by simply scraping it off. 



The formation of scale may be avoided in several ways. Before the brine is 

 run into the vacuum pans, a small amount of calcium chloride may be added 

 and then heated in a grainer-like tank to a temperature of about 150° F (65.6° C). 

 Or a small amount of trisodium phosphate may be sucked into the vacuum pans 

 during the evaporation. The latter operation causes the precipitation of flocculent 

 calcium phosphate, instead of troublesome gypsum. 



A low brine level in the pans and violent agitation of the brine during crystalliza- 

 tion produces small, fine grains of salt; whereas, a higher brine level causes coarser 

 grains. The crystallized salt drops down to the bottom of the vacuum pan and 

 may be drawn off intermittently or caught either in a "salt-catcher," "leg," or 

 "elevator boot." 



As the boiling brine is under a partial vacuum, the level of the brine in the 

 elevator housing above the boot is lower than that in the pan. The salt, contained 

 in a bucket conveyor, passes through the brine in the elevator housing, where it 

 may be washed with a pure salt solution. After washing, it is conveyed in a centri- 

 fuge for partial drying and finally to a revolving cylindrical steam-heated drier, 

 previously described. 



Status of Processing. Although vacuum pan equipment is considerably more 

 costly than grainers having the same capacity, it is generally used for refining 

 because a salt of high quality can be produced with a fraction of fuel and labor 

 cost. Grainer salt is preferred for butter, cheese, and certain other products. 



American Grades of Refined Sea Salt 



The following grades of refined salt are considered commercial California salts: 



No. 1 Mill Salt. Treated and dried salt which is "three-fourths ground" size. 



No. 2 Mill Salt. Salt which is the same as No. 1, although somewhat coarser. 



Coarse Granulated. Treated and dried salt which has been ground to a size 

 suitable for cooking and preserving. 



Fine Granulated. Treated and dried salt which has been ground to a size 

 suitable for table use. 



Bakers' Fine. A grade which is finer than table salt and is used _in dairies and 

 some chemical industries. 



Shaker Salt. Especially prepared table salt, containing finely powdered mag- 

 nesium carbonate or some other substance to produce "free-running" salt. 



The uses for the various qualities of commercial salts are indicated below: 



Hide Curing. Coarse, solar salt. 



Meat Packing. Medium coarse, flaky steam-grainer salt. 



Sheep Salt. Medium fine, crushed solar, crushed rock, or coarse grainer salt. 



Stock Salt. Coarse, cracked solar, rock, hydraulically pressed 50-pound blocks, 

 coarse grainer salt. 



Cheese Salt. Mediinn-flaky grainer salt. 



Butter Salt. Light and medium-flaky steam-grainer salt. For butter and cheese 

 a thin flake permeates better than vacuum or crushed solar salt and does not form 

 local pockets of brine that imparts a stinging, over-salty taste. The more pounds 

 of flakes which can be used for a given quantity of butter, the less costly the 

 product; for salt is cheaper than butter. 



