Standardization of Thiosulfate Using Potassium Dichromate by Direct Titration.

Reliability in standardization of sodium thiosulfate with potassium dichromate

“…If the remaining dichromate caused insufficient oxidation of thiosulfate, it would result in excessive consumption of thiosulfate. Rao and Sarma reported the direct standardization of thiosulfate by potassium dichromate with copper(II) sulfate as a catalyst [18] and mentioned that dichromate directly oxidized thiosulfate to tetrathionate state as usual. Therefore, excessive consumption of thiosulfate was not caused by its insufficient reduction.…”

Kinetic Aspects of Analytical Chemistry

“…Such applications of catalysis in chemical analysis range all the way from the simple use of copper(II) to accelerate the slow oxidation of thiosulfate by dichromate, so as to permit the direct use of this reaction in titrimetry (64), to the highly sophisticated coordination chain reactions of Margerum (45~47) for the selective determination of metals at ultra-trace concentration levels. The latter method utilizes reaction systems involving ligand exchange between metal complexes, such as triethylenetetraminenickel(II) and (ethylenedinitrilo)tetraacetatocuprate (II), by chain reaction mechanisms where the chain centers are the free ligands.…”