Determination of a Mixture of Selenocyanate and Cyanide Ions by Short-circuit Amperometric Titration

Abstract

Selenocyanate ion in a neutral supporting electrolyte (such as potassium nitrate) was titrated with a silver nitrate solution by the use of short-circuit amperometry using a rotating platinum wire electrode (1000 rpm) as an indicator electrode and SCE as a reference electrode.
It was found that selenocyanate ion could be titrated at the concentration range of 0.01, 0.00001 moll and a 0.001 molg selenocyanate solution was titrated most precisely with the relative error and the coefficient of variation of less than 0.1%.
A method for the determination of a mixture of selenocyanate and cyanide ions was as follows: The sum of selenocydnate and cyanide was titrated similarly for an aliquot of the sample solution. Another aliquot of the same solution was titrated to the end point of seleno- cyanate after masking cyanide ion with excess formalin and adjusting the pH to 6 with the dilute nitric acid.