Overview
ISO 17489:2013 - Leather - Chemical tests - Determination of tan content in synthetic tanning agents - defines a practical laboratory method to measure the adsorbable fraction (tan content) of synthetic tanning agents. The method uses a crosslinked, insoluble vinylimidazole/vinylpyrrolidone copolymer as the adsorbent instead of traditional hide powder. ISO 17489 is designed for routine quality control and batch-to-batch consistency checks in synthetic tanning agent production.
Key topics and technical requirements
- Principle: Acidify an aqueous solution of the synthetic tanning agent, mix with the insoluble copolymer which adsorbs polyphenolic tanning components, then measure dry residue before and after adsorption. The difference gives the tan content (adsorbable fraction).
- Reagents & materials: Crosslinked vinylimidazole/vinylpyrrolidone copolymer (e.g., Divergan-type products), formic acid (50 %), gelatine, sodium chloride, and laboratory-grade water per ISO 3696.
- Apparatus: Analytical balance, drying oven (105 °C ±2 °C), magnetic stirrer, pH meter, filtration (0.45 µm) or centrifugation capability, and standard glassware.
- Procedure essentials: Prepare duplicate acidic tanning solutions, determine total dry content and non-adsorbable fraction (filtrate), verify absence of residual tanning agent with a gelatine/NaCl check, and calculate % tan content = % dry content − % non-tanning agent content.
- Quality checks & reporting: Two determinations are required; report the mean to one decimal place. If duplicates differ by more than 0.5 % tan content, repeat the test. Test report must reference ISO 17489 and list sample description, result, and any deviations.
- Performance: Interlaboratory trials reported in the standard show good reproducibility and improved repeatability compared with hide powder methods.
Applications
- Routine quality control of synthetic tanning agents during manufacturing.
- Batch-to-batch consistency monitoring for suppliers and formulators of tanning products.
- Rapid in-plant testing where the traditional hide powder method (ISO 14088) is impractical or too slow.
- Development and verification of synthetic tanning formulations where accurate measurement of the adsorbable tanning component is needed.
Who should use this standard
- Leather chemists and laboratory technicians performing leather chemical tests.
- Producers of synthetic tanning agents, leather tanneries, and QC laboratories.
- R&D teams validating tanning strength and adsorption characteristics of synthetic tannins.
Related standards
- ISO 14088 - quantitative analysis of tanning agents by the traditional hide powder/filter method (reference method for comparison).
- ISO 3696 - specification for laboratory water used in the procedure.
Keywords: ISO 17489:2013, tan content, synthetic tanning agents, vinylimidazole/vinylpyrrolidone copolymer, leather chemical tests, adsorbable fraction, quality control, batch-to-batch consistency.