Abstract: A deductive analytical method, using measurements of specific conductivity and pH, for determining the concentration of a desired ion in a sample which may contain multiple ionic species without removal of the ions from solution is disclosed. The method involves the steps of: measuring the specific conductivity and the pH of the sample and of a reagent; adding an excess of the reagent capable of reacting with the desired ion, e.g. causing precipitation, thereby reducing the specific conductivity of the sample; measuring the pH and specific conductivity of the sample-reagent mixture; comparing the pH and specific conductivity values of the sample, the reagent and the reaction product of the sample and reagent; and deducing the concentration of the measured ion from these values by calculation.