Determination of polythionates and thiosulphate in mining effluents and mill circuit solutions

A method is described for the determination of total polythionates plus thiosulphate by acidimetric titration. The titration can be carried out either at the Methyl Orange (pH = 4.30) or at the phenolphthalein (pH = 8.20) end-point, with standard sodium hydroxide solution, to determine the amount of acid produced on oxidation of the thiosulphate and polythionates. The precision and accuracy are good and samples containing as little as 0.1 mg of the thio salt can be analysed very easily. Results obtained by this method are compared with those obtained by a calorimetric method and are in good agreement.