Abstract: In a purification process for brine, impurities such as calcium, magnesium and/or sulphate are precipitated by the addition of calcium hydroxide (Ca(OH).sub.2) and sodium carbonate (Na.sub.2 CO.sub.3). Following NaCl crystallization by evaporation of the brine, a mother liquor is obtained which still contains among others sulphate, potassium and bromide ions. Further concentration of this mother liquor by evaporation results in the precipitation of both NaCl and Na.sub.2 SO.sub.4 and a more strongly concentrated mother liquor with respect to both potassium and bromide remains. This concentrated mother liquor is drained off. Either the precipitated NaCl and Na.sub.2 SO.sub.4 are dissolved in water or the Na.sub.2 SO.sub.4 is dissolved in purified brine or crude brine and then returned to the brine purification process, thereby lowering both the potassium and bromide ion levels in the purified brine. As a consequence the contents of both potassium and bromide of the NaCl are reduced.