On the standardisation of permanganate by arsenious oxide

Abstract

Potassium iodide and potassium iodate are known to act as catalysts in the reaction between arsenious oxide and potassium permanganate in the presence of hydrochloric acid and this has been employed in the standardisation of permanganate solutions using arsenious oxide as a primary standard. It has been observed that besides these salts, aqueous iodine and bromine, potassium bromide and potassium bromate also exert a catalytic influence on the reaction. It is now recommended to carry on the titration of 0.1 N arsenious oxide against potassium permanganate using 10–15 ml of 4 N hydrochloric acid for acidifying the medium, and two drops of 2.5 × 10−3 M solution of the catalyst. It has also been reported here that of all the catalysts, potassium iodate gives the most sharp end point, though the results yielded appear to be about 0.2% too low.