Sodium chloride crystals of table salt quality - by mixing recrystallised and washed crude salt

摘要

Crystalline sodium chloride of uniform grain size 0.3-0.5 mm of table salt quality, purity 98.5-99.5%, and retaining health-giving trace impurities such as iodides, is obtained by mixing recrystallised salt with 25-70% of washed crude salt (depending on the degree of purity) of approx. the same grain size. Washing is achieved by slurrying the crude salt with a sat. soln. of crude salt and feeding the slurry into an evaporative crystalliser in which pure salt crystallises from the sat. soln. and the crude salt is washed by the mother liquor.