After considerable investigation, it is believed that the most rapid, accurate method for the determination of sodium chlorate in cell liquor produced in chlorine manufacture is the reduction of the chlorate with excess ferrous ammonium sulfate in 40% hydrochloric acid by volume. Ammonium molybdate is used as the catalyst. The method is accurate to within about 1 %, of the amount of chlorate present. It permits greater precision than the sodium arsenite-potassium brómate method.The sample of cell liquor for the sodium chlorate estimation may also serve for a total alkalinity determination if standard hydrochloric acid is used in the initial neutralization process.