Overview
EN ISO 5398-1:2018 - Leather: Chemical determination of chromic oxide content, Part 1: Quantification by titration specifies a laboratory method to determine total chromium (reported as chromic oxide) in leather. The procedure solubilizes chromium in the hexavalent state and quantifies it by iodometric titration. It is intended for chromium‑tanned leathers with chromic oxide contents typically in excess of 0.3%. The standard addresses sample preparation, two alternative routes to obtain a suitable aqueous solution, titration reagents and apparatus, calculation, repeatability and reporting.
Key topics and requirements
- Scope and principle: Total chromium determination (not compound‑ or oxidation‑state specific); chromium solubilized as hexavalent chromium and measured by iodometric titration.
- Two sample‑preparation alternatives:
- Wet oxidation method (nitric acid, sulfuric/perchloric mixture) - caution required due to reactive oxidizers.
- Alkaline fusion method (fusion mix of Na2CO3, K2CO3 and sodium tetraborate) followed by acid dissolution.
- Reagents for iodometric titration: potassium iodide (fresh), standardized 0.1 mol/L sodium thiosulfate, starch indicator.
- Apparatus: common laboratory glassware (500 mL conical flask, 50 mL burette), crucible for fusions, filtration devices, antibu mping granules.
- Sampling and sample prep references: sampling per ISO 2418 and test sample preparation per ISO 4044.
- Reporting and accuracy: calculation/expression of chromic oxide content on a dry matter basis, minimum two determinations per sample, and repeatability criteria provided.
Applications
- Quality control in tanneries: monitor chrome pickup and consistency in chrome‑tanned leathers.
- Laboratory testing and certification: routine chemical analysis for product specifications and internal QA.
- Regulatory and compliance checks: baseline total chromium content reporting for environmental and safety documentation (note: method does not distinguish Cr(III) vs Cr(VI)).
- Process troubleshooting: assess effectiveness of tanning processes and raw material variability.
Who should use this standard
- Leather chemists and technologists
- Industrial and contract testing laboratories
- Tanneries and leather manufacturers
- Product compliance officers and environmental testing units
Related standards
- ISO 2418 - Sampling location for leather tests
- ISO 4044 - Preparation of chemical test samples
- ISO 3696 - Water for analytical laboratory use
- ISO 4047 - Determination of sulphated ash
- ISO 4684 - Determination of volatile matter
Keywords: EN ISO 5398-1:2018, chromic oxide, chromium determination, iodometric titration, leather testing, wet oxidation, alkaline fusion, total chromium.