ISO 2463:1973

Overview

ISO 2463:1973 specifies a mercurimetric titration method for determining the chloride content of industrial sodium chlorate. The method is applicable to samples with chloride levels greater than 0.01% (m/m) and is not suitable for mixed formulations (e.g., herbicides or insecticides). The principle is a volumetric titration of chloride ions with mercury(II) nitrate using diphenylcarbazone as the end-point indicator.

Key topics and technical requirements

• Scope: Analysis of sodium chlorate for industrial use; excludes mixtures and low-chloride samples (<0.01% m/m).
• Principle: Titration of Cl– with standard Hg(II) nitrate solution in the presence of diphenylcarbazone; endpoint assessed by colour change to mauve.
• Reagents: Distilled water; nitric acid (approx. 14 N and ~2 N solutions); 0.1 N mercury(II) nitrate standard solution; 0.1 N sodium chloride reference solution; bromophenol blue and diphenylcarbazone indicator solutions.
• Preparation and standardization: A standard end-point matching solution is prepared (bromophenol blue + nitric acid, adjusted to yellow then excess, plus diphenylcarbazone) and the Hg(II) nitrate solution is standardized against a sodium chloride reference (40.00 ml).
• Procedure essentials: Typical test portion is 10.0 g; sample dissolved in water, acidified to change bromophenol blue from blue to yellow (with an excess), matched with diphenylcarbazone, then titrated to the mauve endpoint with the standardized mercury(II) nitrate.
• Result expression: Chloride content is reported as percentage by mass expressed as sodium chloride (NaCl) and results are given to two decimal places.
• Safety: Sodium chlorate is an oxidizer that can induce combustion-avoid heat and contact with combustible/fatty materials; rinse any contaminated materials thoroughly.

Applications and users

• Quality control laboratories in industrial sodium chlorate production.
• Chemical analysis and metrology laboratories performing volumetric (titrimetric) chloride determinations.
• Regulatory, procurement, and materials testing teams requiring a standardized method for reporting chloride impurity levels in sodium chlorate.
• Useful where a reliable, classical titrimetric method (mercurimetric method) is preferred over instrumental techniques.

Related standards

• Developed by ISO Technical Committee ISO/TC 47 (Chemistry).
• Relevant for laboratories interested in standardized volumetric analysis, titration methods, and chemical quality control procedures for industrial oxidizers.

Keywords: ISO 2463:1973, sodium chlorate, chloride determination, mercurimetric method, mercury(II) nitrate titration, diphenylcarbazone, volumetric analysis, industrial sodium chlorate.