Overview
ISO 1833-26:2020 - Textiles - Quantitative chemical analysis - Part 26 - specifies a chemical method using hot formic acid to determine the mass percentage of melamine fibres in textile mixtures after removal of non-fibrous matter. The scope covers blends of melamine with cotton, polypropylene or aramid fibres. The method is part of the ISO 1833 series for textiles quantitative chemical analysis and is intended for laboratory determination of fibre composition by selective dissolution.
Key topics and requirements
- Principle: dissolve melamine fibres from a known dry mass of the textile mixture using hot 90% (mass fraction) formic acid; collect, wash, dry and weigh the insoluble residue; calculate melamine content by difference.
- Reagents:
- Formic acid reagent: 90% by mass (prepared by diluting 890 ml of 98–100% formic acid to 1 L).
- Dilute ammonia solution (80 ml concentrated ammonia to 1 L).
- Use other reagents as specified in ISO 1833-1.
- Safety note: formic acid is harmful - full precautions required.
- Apparatus:
- Conical flask (≥200 ml) with glass stopper.
- Shaking water bath or equivalent providing ~160 cycles/min and maintaining (90 ± 2) °C.
- Procedure highlights:
- Use ~100 ml formic acid per gram of specimen; maintain shaking at 90 °C for 1 hour.
- Decant and filter through a weighed crucible, perform additional acid washes, then wash sequentially with hot water, dilute ammonia, and cold water.
- Dry, cool and weigh residue; apply correction factor for reagent insoluble component (d = 1.02).
- Precision: confidence limits on homogeneous mixtures are ±2 percentage point (95% confidence).
Applications and users
- Routine laboratory analysis for textile manufacturers, quality control and assurance teams, independent testing laboratories, and material verification specialists who need accurate quantitative chemical analysis of fibre blends.
- Useful for compliance testing, product labeling verification, forensic textile analysis, and raw material inspection where detection and quantification of melamine in blends with cotton, polypropylene or aramid is required.
- Relevant to R&D groups optimizing blend compositions and to procurement or regulatory bodies verifying declared fibre content.
Related standards
- ISO 1833-1: General principles for quantitative chemical analysis of textiles - referenced norm for general procedures and calculations.
- Other parts of the ISO 1833 series cover selective dissolution and determination methods for different fibre mixtures.
Keywords: ISO 1833-26, melamine fibres, hot formic acid method, textiles quantitative chemical analysis, cotton, polypropylene, aramid, fibre composition testing.