Reliability in Standardization of Iron(III) and Titanium(III) Solutions in Volumetric Analysis.

Toshiaki Asakai,Toshihiro Suzuki

doi:10.1021/acsomega.1c03074

Toshiaki Asakai, Toshihiro Suzuki

Open Access

https://doi.org/10.1021/acsomega.1c03074

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Abstract

Titanium(III) is a useful strong reductant and is usually standardized with iron(III) in volumetric analysis. Iron(III) is widely used as an oxidant and is usually standardized with thiosulfate ions through an iodine liberation reaction. The evaluation of the standardization procedure for iron(III) with thiosulfate ions is therefore essential to ensure the reliability of standardized titanium(III) solutions. To investigate the titration procedure for iron(III), two different titrations were performed: redox titration with thiosulfate ions through an iodine liberation reaction and chelatometric titration with disodium dihydrogen ethylenediaminetetraacetate. Subsequently, for the investigation of standardization of iron(III), titanium(III) was assayed through two titration paths: redox titration with standardized iron(III) and redox titration with standard potassium dichromate. The reliability of titrimetric procedures was evaluated by applying several different stoichiometric reactions to each chemical. All titrimetric procedures were consistent with each other within their expanded uncertainties and were capable of providing reliable volumetric standards with careful operations presented in this study.

Highlights

A reliable titanium(III) standard solution became necessary when the authors were trying to determine the purity of the perchlorate salt.[1]
Perchlorate explosively reacts with organic materials; in contrast, the stoichiometric reduction of perchlorate is more difficult in a series of oxyanions of chlorine due to its inactivity.[2,3]
The aim of the present study is to evaluate the reliability of the titrimetric procedures for iron(III) and titanium(III) as a volumetric standard

Summary

Introduction

A reliable titanium(III) standard solution became necessary when the authors were trying to determine the purity of the perchlorate salt.[1]. Titanium(III) is often standardized with iron(III).[4] Iron(III) is usually standardized with thiosulfate through an iodine liberation reaction.[5,6] Thiosulfate is usually standardized with a certified reference material (CRM) of iodate or dichromate. These titrimetric methods play a key role in the accuracy of the titration results.[7] Useful metrological information on the reliability of the volumetric standards such as these very weak oxidant and very strong reductant has not been found. A standardization procedure for iron(III) is as follows: iodine (triiodide ions) liberated by iron(III) in an acidic potassium iodide solution (eq 1) is titrated with a sodium thiosulfate solution (eqs 2 and 3); the sodium thiosulfate solution is standardized with standard potassium iodate or potassium dichromate (eqs 2 and 3):

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