The official method for the determination of Cl^- and SO^2-₄ in food coal-tar dyes gave low results because of the adsorption of significant amounts of the ions on activated charcoal. Automatic potentiometric titration method, which the titration stopped automatically at a setting potential, was applied to the determination of Cl^- in the dyes. The condition of electrode potential having a constant value at the end point was examined, and Cl^- was automatically determined rapidly and simply with less than 1% error. SO^2-₄ in azo and triphenylmethane dyes was separated from the dyes by extraction with Amberlite LA-2 and determined with less than 2% error by chelate titration method with EDTA after adding excess barium nitrate. SO^2-₄ in Acid Red was directly determined with less than 2% error by chelate titration method using potentiometric end point detection, because it was found that the dye containing sulfonic acid groups in the molecule was not precipitated by Ba²⁺.