Overview - ISO 4098:2018 (IULTCS / IUC 6)
ISO 4098:2018 specifies a standardized laboratory method for the chemical analysis of leather to determine water‑soluble matter, water‑soluble inorganic matter, and water‑soluble organic matter. Applicable to all leather types, the method prescribes sample preparation, aqueous extraction, evaporation/drying, sulfatation and ignition to obtain consistent, comparable results when test conditions are reproduced exactly.
Key topics and technical requirements
- Scope: method applies to all types of leather for quantifying water‑soluble fractions and their inorganic/organic split.
- Sample preparation and sampling: follow ISO 4044 (sample preparation) and ISO 2418 (sampling location) before extraction.
- Extraction conditions: specified water volume, extraction temperature (23.5 ± 3.5 °C) and mechanical agitation for a defined period (120 ± 10 min). The standard notes results depend strongly on degree of grinding, extraction temperature, extraction time and leather:water ratio - reproducibility is essential.
- Determination of totals:
- Evaporate aliquots of filtrate and dry residue at (102 ± 2) °C to determine total water‑soluble matter.
- Sulfate and ignite the dried residue (calcination at up to 700 °C) to obtain water‑soluble inorganic matter.
- Calculate water‑soluble organic matter by difference (total minus inorganic).
- Special considerations:
- Ammonium salts in filtrate are included in water‑soluble matter and are decomposed on ignition, thus affecting the organic fraction; their concentration may be determined separately if required.
- Use of appropriate laboratory apparatus (analytical balance, drying oven, muffle furnace, filtered aliquots, etc.) and laboratory water quality per ISO 3696.
- Result expression: results are calculated as percentages of the original sample mass; optionally expressed on a dry‑matter basis using moisture data (ISO 4684).
Practical applications
- Quality control and specification of leather raw materials and finished goods.
- Comparative assessment of tanning, retanning or finishing processes that influence extractable substances.
- Laboratory testing for product development and materials evaluation where water‑soluble residues are relevant.
- Generation of reproducible analytical data for supplier verification and contract testing.
- Leather testing laboratories and R&D teams
- Tanneries and finishing houses
- Footwear, apparel and leather goods manufacturers with incoming/raw material QA
- Standards and compliance officers specifying analytical methods
Related standards
- ISO 4044 - Sample preparation for chemical tests
- ISO 2418 - Sampling location for leather
- ISO 4684 - Determination of volatile matter (for dry‑basis reporting)
- ISO 3696 - Laboratory water quality
- ISO 4048 - Soluble matter in dichloromethane (related chemical tests)
Keywords: ISO 4098, leather chemical tests, water‑soluble matter, water‑soluble inorganic matter, water‑soluble organic matter, IULTCS, IUC 6, leather testing.