Heavy metal impurities, especially of lead, in reagent grade sodium chloride were extracted with dithizone and quantitatively estimated by polarography. In order to examine the percentage of extraction of lead by dithizone, 20-60γ lead was extracted from 150-450ml. aqueous sodium chloride solution at pH 9 with dithizone-carbon tetrachloride, rextracted with hydrochloric acid, the hydrochloric acid evaporated off, the residue dissolved in tartaric acid-ammonium acetate supporting electrolyte and polarogram was recorded. The result showed that the percentage of extraction of lead was 95 %, and, in case of insufficient evaporating operation, it caused an appearance of waves due to the presence of decomposition product of dithizone and it disturbed the estimation of wave height of lead and the detection of other metals. Quantitative estimation of lead was made on 4 samples of sodium chloride; also, lead, zinc, copper and a trace of nickel were detected by a combined use of potassium thiocyanate-ammonium acetate supporting electrolyte.