Overview
EN ISO 4047:1998 (ISO 4047:1977) specifies a laboratory method for determining the sulphated total ash and sulphated water‑insoluble ash of leather. Published by CEN/ISO and applicable to all types of leather, the standard defines the carbonization of leather followed by sulphuric‑acid treatment and controlled ashing to quantify inorganic (mineral) content as part of a complete leather analysis.
Keywords: EN ISO 4047:1998, ISO 4047, sulphated total ash, sulphated water‑insoluble ash, leather analysis, ash content, mineral content of leather, leather testing.
Key Topics and Requirements
- Scope and applicability: Method applies to all leather types; useful in complete leather analyses to determine inorganic matter.
- Principle: Carbonize sample → moisten with ~2 N sulphuric acid → ash in open crucible at controlled temperature (close to, but not exceeding, 800 °C).
- Reagents: Analytical grade reagents; distilled water. Explicitly referenced:
- Sulphuric acid, approx. 2 N.
- Ammonium nitrate solution (~100 g/L) to assist removal of residual carbon if needed.
- Apparatus: Glazed porcelain, platinum or quartz crucibles; muffle furnace controllable at ≈800 °C.
- Sampling & sample prep: Follow ISO 2588, ISO 2418 and prepare test samples per ISO 4044. Typical test mass: 2–5 g, weighed to 0.001 g.
- Calculations:
- Sulphated total ash (%) = (mass of sulphated total ash / mass of original sample) × 100
- Sulphated water‑insoluble ash (%) = (mass of sulphated water‑insoluble ash / mass of original sample) × 100
- Limitations & notes: Ammonium salts are not determined by this method. Organo‑metallics (e.g., silicones) can affect accuracy; volatile inorganic salts may be lost above 800 °C so temperature control is critical.
- Repeatability: Duplicate determinations by the same operator should not differ by more than 0.1% (absolute, based on original sample mass).
- Reporting: Include reference to the standard, sample identification, results to one decimal place and any special circumstances.
Applications and Users
- Quality control laboratories in tanneries and leather manufacturers
- Third‑party testing and certification bodies performing leather testing and composition analysis
- Research laboratories assessing mineral content of leather or studying effects of tanning/finishing processes
- Regulatory or compliance testing where ash content or inorganic residues are relevant
Practical uses include monitoring raw material and finished‑product consistency, troubleshooting processing issues related to inorganic additives, and supporting component analysis (e.g., chromium, aluminium) after ash retention.
Related Standards
- ISO 4044 - Preparation of chemical test samples (leather)
- ISO 4098 - Determination of water‑soluble and water‑soluble inorganic matter
- ISO 2588 - Sampling: number of items for a gross sample
- ISO 2418 - Laboratory sample location and identification
For accurate implementation, use EN ISO 4047:1998 together with the referenced ISO methods for sampling and sample preparation.
