ISO 1833-22:2020

Overview - ISO 1833-22:2020 (Textiles quantitative chemical analysis)

ISO 1833-22:2020 specifies a chemical dissolution method to determine the mass percentage of viscose (and certain types of cupro, modal or lyocell) in textile mixtures with flax fibres. The procedure uses a formic acid / zinc chloride reagent after pre‑treatment to remove non‑fibrous components of flax. The standard defines sample preparation, reagents, apparatus, test conditions, calculation methods and precision limits for compositional analysis.

Key topics and technical requirements

• Scope and limitations: Applicable to mixtures of viscose (or specified cupro, modal, lyocell) with flax; not applicable when flax is extensively chemically degraded or when the soluble fibre is rendered incompletely soluble by permanent finishes or reactive dyes.
• Principle: Remove non‑cellulosic flax components by alkaline pre‑treatment, dissolve the soluble man‑made cellulosic component in a formic acid/zinc chloride reagent, recover and weigh the insoluble residue, and compute component percentages by difference.
• Reagents and composition: Formic acid/zinc chloride reagent prepared (per 100 g) from ~20 g anhydrous ZnCl2 and ~68 g anhydrous formic acid (made up to 100 g with water). Acetic acid (0.1 mol/L) and dilute ammonia for neutralisation are also specified.
• Test conditions: Preheated reagent and sample at 70 ±2 °C; dissolution for 20 minutes with intermittent shaking; filtration, washing, ammonia immersion and rinsing steps described in the method.
• Apparatus: Minimum 200 ml glass‑stoppered conical flask, heating apparatus able to maintain 70 °C, weighed filter crucible.
• Calculations: Formulas for loss during pre‑treatment, corrected dry mass, component dry masses and percentage results including agreed moisture additions. Specified correction (d‑) factors:
  • Raw fibres: d1 (viscose/cupro/modal/lyocell) = 1.05; d2 (flax) = 1.04
  • Bleached fibres: d1 = 1.16; d2 = 1.07
• Precision: Confidence limits not greater than ±3 percentage points at 95% confidence on homogeneous mixtures.

Applications and users

• Quality control and compositional verification in textile manufacturing and finishing
• Accredited textile testing laboratories performing blend analysis and labeling verification
• Textile chemists, material scientists and R&D teams analyzing fiber blends (viscose/cupro/modal/lyocell + flax)
• Regulatory and certification bodies requiring standardized quantitative fibre analysis

Use ISO 1833-22:2020 for reliable, repeatable measurement of fiber blend proportions where formic acid/zinc chloride dissolution is appropriate. Always follow laboratory safety, waste disposal and the pre‑treatment guidance in ISO 1833-1:2020.

Related standard

• ISO 1833-1:2020 - Textiles - Quantitative chemical analysis - Part 1: General principles of testing (normative reference for general procedure and pre‑treatment).