ISO 5398-1:2018

Overview

ISO 5398-1:2018 sets the international standard for the chemical determination of chromic oxide content in leather through a quantification method by titration. This standard, developed by ISO in collaboration with the International Union of Leather Technologists and Chemists Societies (IULTCS) and the European Committee for Standardization (CEN), details a reliable and industry-accepted technique for analyzing total chromium content in chromium-tanned leather samples.

This method enables the determination of total chromium (reported as chromic oxide) in aqueous solutions derived from leather, without specifying chromium’s chemical compounds or oxidation states. It is primarily designed for chromium-tanned leathers with chromic oxide content exceeding 0.3%, offering two alternative procedures for sample analysis.

Key Topics

• Scope and Applicability

  • Quantitative chemical analysis of total chromium in leather, expressed as chromic oxide (Cr₂O₃) content by mass.
  • Suitable for chromium-tanned leather types with chromic oxide content over 0.3%.
  • Two preparatory methods for chromium extraction: wet oxidation and alkaline fusion.

• Sampling and Preparation

  • Leather samples prepared according to ISO 2418 (sampling location) and ISO 4044 (sample preparation).
  • Accurate mass measurements with suggested sample sizes based on chromium content.

• Analytical Techniques

  • Wet oxidation involves acid digestion with nitric acid and a sulfuric/perchloric acid mixture to oxidize chromium.
  • Alkaline fusion uses a mixture of sodium carbonate, potassium carbonate, and sodium tetraborate to ash the leather sample before dissolution.
  • Both methods yield aqueous solutions for iodometric titration.

• Iodometric Titration

  • Chromic oxide content is determined by titrating potassium iodide-treated solutions with standardized sodium thiosulfate using starch as an indicator.
  • Precise titrant volume measurements allow conversion to chromic oxide percentage.

• Calculations and Reporting

  • Results expressed as percentage chromic oxide on a dry matter basis, corrected for volatile matter content obtained per ISO 4684.
  • Repeatability requires duplicate tests to not differ by more than 0.1%.
  • Test reports must document sampling, method details, volatile matter content, and any deviations.

Applications

ISO 5398-1:2018 is highly valuable to a range of stakeholders within the leather industry and quality control laboratories, including:

• Leather Manufacturers
  Ensures consistent quality control of chromium-tanned leathers, meeting regulatory and internal standards for chemical content.

• Chemical Testing Laboratories
  Provides an established and internationally recognized protocol for precise chromium quantification, enabling cross-lab comparability.

• Regulatory and Compliance Bodies
  Facilitates enforcement of environmental and safety regulations related to chromium use in leather processing.

• Research and Development
  Supports development of new tanning processes and materials by providing accurate, repeatable chemical characterization methods.

Related Standards

• ISO 2418 – Leather - Sampling location for chemical, physical, mechanical, and fastness testing.
• ISO 3696 – Water for analytical laboratory use - Specification and test methods.
• ISO 4044 – Leather - Chemical tests - Preparation of chemical test samples.
• ISO 4047 – Leather - Determination of sulphated total ash and sulphated water-insoluble ash.
• ISO 4684 – Leather - Chemical tests - Determination of volatile matter.

These complementary standards support the accurate implementation of ISO 5398-1:2018 by defining preparatory, sampling, and analytical conditions essential for reliable leather testing.

By adhering to ISO 5398-1:2018, leather industry professionals can perform standardized, titration-based chemical determinations of chromic oxide content, ensuring product quality, safety, and regulatory compliance in chromium-tanned leather applications.