Determination of potassium and sodium in mixtures of their salts by means of cation exchangers

Methods for the determination of two substances in aqueous solutions (or water-soluble mixtures) are described. A sample of the solution is dried and the residue accurately weighed. Another sample of the same volume is passed through a cation exchanger (when cations are to be determined), saturated with one of the ions in the solution. After washing with distilled water the combined effluent and wash-water are dried and the residue carefully weighed. From these weighings the composition of the solution is determined by simple calculations, the maximum relative error being < 2.0%. The method may be used for the determination of anions, if an anion exchanger is used instead of the cation exchanger.A variation of the method consists in passing the solution through a cation exchanger in the hydrogen form. The number of equivalents is determined by standard alkali titration and from this and the weight before the ion-exchange passage the composition of the solution can be determined. In this case, however, the maximum relative error is larger. This method is directly applicable to the determination of anions.