Overview
EN ISO 1833-22:2021 (ISO 1833-22:2020) specifies a quantitative chemical test method for determining the mass percentage of viscose or certain types of cupro, modal or lyocell in textiles that are blended with flax fibres. The method uses a formic acid / zinc chloride reagent to dissolve the viscose-type components after pre‑treatment to remove non-fibrous matter. It is adopted by CEN and supersedes EN ISO 1833-22:2013.
Key topics and technical requirements
- Scope & exclusions
- Applicable to mixtures of viscose (and some cupro, modal or lyocell) with flax.
- Not applicable if flax has undergone extensive chemical degradation or if viscose/cupro/modal/lyocell is rendered incompletely soluble by permanent finishes or reactive dyes.
- Principle
- Remove non-cellulosic components from flax (pre-treatment with sodium hydroxide per ISO 1833-1).
- Dissolve viscose/cupro/modal/lyocell using a formic acid/zinc chloride reagent.
- Collect, wash, dry and weigh the residue; determine fibre percentages by mass difference and corrected dry mass.
- Reagents & apparatus
- Formic acid/zinc chloride reagent: prepared with 20 g anhydrous ZnCl2 and 68 g anhydrous formic acid made up to 100 g with water.
- Supporting reagents: 0.1 mol/L acetic acid solution and dilute ammonia (for neutralization).
- Equipment: conical flask (≥200 ml), heating apparatus capable of (70 ± 2) °C, weighed filter crucible.
- Procedure parameters
- Dissolution performed at 70 °C for 20 minutes with intermittent shaking; filter, wash, dry and weigh residue.
- Calculations include corrections for pre-treatment mass loss and application of d-factors (updated in this edition).
- Documentation
- Clause references and precision information are included; users must follow ISO 1833-1 general principles for test organisation.
Applications and users
- Who uses it
- Textile testing laboratories, quality assurance teams, fibre suppliers, manufacturers of blended fabrics, certification and compliance bodies, research institutions.
- Practical uses
- Verifying declared fibre composition for labelling and regulatory compliance.
- Quality control of viscose–flax, modal–flax or lyocell–flax blends.
- Supplier acceptance testing and raw material inspection.
- Research into fibre blends, biodegradability and performance of cellulose-based composites.
Related standards
- ISO 1833-1:2020 - General principles of quantitative chemical analysis for textiles (normative reference).
- EN ISO 1833 series - other parts cover different fiber combinations and test methods.
Keywords: EN ISO 1833-22:2021, textile quantitative chemical analysis, viscose flax mixtures, formic acid zinc chloride method, cupro modal lyocell, fibre composition testing.
