Overview
EN ISO 1833-5:2010 (identical to ISO 1833-5:2006) is a standardized chemical test method for textiles that specifies how to determine the percentage of viscose, cupro or modal fibres in binary mixtures with cotton fibres. The method uses sodium zincate to dissolve the regenerated cellulosic component (viscose/cupro/modal) after removal of non‑fibrous matter, leaving the cotton residue to be collected, dried and weighed. Results are expressed as the percentage of viscose/cupro/modal in the original dry mass.
Key topics and technical requirements
- Scope and applicability
- Intended for binary mixtures of viscose (or most current cupro/modal fibres) with raw, scoured, kiered or bleached cotton.
- Not applicable if cotton has undergone extensive chemical degradation or if viscose/cupro/modal are rendered incompletely soluble (e.g., certain permanent finishes or reactive dyes that cannot be fully removed).
- When cupro or modal is present, a preliminary solubility test in the reagent is required.
- Principle
- Dissolve viscose/cupro/modal in a sodium zincate solution; collect, wash, dry and weigh the insoluble cotton residue. Percentage of viscose/cupro/modal = difference from the original dry mass.
- Reagents
- Sodium zincate stock solution prepared from NaOH and zinc oxide (filtered before use).
- Working (dilute) sodium zincate: 1 part stock + 2 parts water - use within 24 hours.
- Dilute ammonia and dilute acetic acid for washing steps.
- Apparatus and procedure highlights
- Mechanical shaker and stirrer, glass conical flask (≥500 ml), weighed filter crucible.
- Typical reagent volumes given: 150 ml dilute sodium zincate per gram of specimen; subsequent washes with ~100 ml ammonia and 100 ml acetic acid; gravity drainage between washings; final suction, drying and weighing.
- Calculation
- Follow ISO 1833-1 general instructions. The document specifies a correction factor (d) of 1.02 for raw/scoured/kiered/bleached cotton.
Practical applications and users
- Who uses it
- Textile testing laboratories, quality control teams, fibre analysts, manufacturers, import/export inspectors and regulatory bodies.
- Why use it
- Routine quantitative fibre composition analysis for blended fabrics and garments.
- Verification of labelling claims, quality assurance in supply chains, dispute resolution for fibre content.
- Limitations to consider
- Pre-test solubility checks for cupro/modal and awareness of finishes or dyes that may interfere with solubility and measurement accuracy.
Related standards
- ISO 1833-1: General principles of testing (referenced for general procedures and calculations).
- Other ISO 1833 parts cover quantitative methods for different fibre mixtures (see ISO 1833 series for acetate, polyester, polyamide, etc.).
Keywords: EN ISO 1833-5:2010, ISO 1833-5, sodium zincate, viscose, cupro, modal, cotton fibres, quantitative chemical analysis, textile testing, fibre composition.
