The application of the varying weights of bischofite dissolved in the distilled water was investigated. The effects of the temperature on the rate of evaporation and the thermal precipitation time on the purity of the crystal products were fully investigated. Two validation tests including magnifying tests and recycling residue were also studied. Our results demonstrate that the contents of NaCl KCl and CaSO4 in the filtrate reached a minimum value after the pretreatment of 350 g bischofite

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... olved in 100 ml distilled water. In the crystal products from the second evaporating stage of the validation tests, the contents of MgCl2·6H2O, SO4 and NaCl+KCl are 99%, ≤0.1±0.01% and ≤0.8±0.04%, respectively. The content of magnesium chloride in the solution was increased to a greater extent, and the impurities reduced correspondingly through the dissolution pretreatments of bischofite. This could decrease energy consumption for the impurity removing stage, evaporation and crystallization process, and thus reduce costs for the industrial production of food-grade magnesium chloride