Sodium meta-vanadate as volumetric reagent: Iodine monochloride method

Abstract

In hydrochloric acid medium sodium meta-vanadate was used as a volumetric reagent for the determination of copper, zinc, cobalt, mercury, and lead. Cu +2, Zn +2 and Co +2were precipitated as complex mercurythiocyanates, Hg +2 as mercuric zinc thiocyanate and Pb +2 as Iodide. The thiocyanates were dissolved in concentrated hydrochloric acid and titrated against standard sodium meta-vanadate solution in the presence of iodine monochloride as a pie.oxidizer and catalyst. In titration of the iodide against the meta-vanadate. it was not necessary to add iodine monochloride to the titrant because it is formed during the titration. Chloroform was used as an indicator. It was pink owing to the liberation of iodine during the titration and became pale yellow at the end-point because of the formation of iodine monochlonde.