ISO 3072:1975

Overview

ISO 3072:1975 - Wool - Determination of solubility in alkali specifies a laboratory test method to measure the alkali solubility of wool. The test quantifies the loss in dry mass after immersion in a controlled sodium hydroxide solution and gives an index of chemical change caused by treatments (acid, oxidizing/reducing agents, heat, light or alkalis). The procedure is most useful for quality control and comparison with an untreated control.

Key topics and requirements

• Scope and applicability: Applies to wool in any form (loose fibre, sliver, roving, yarn, cloth). Best interpreted when an untreated control sample is available.
• Principle: Immersion of wool in 0.1 N sodium hydroxide under specified time, temperature and volume, followed by determination of mass loss as percentage of dry mass (alkali solubility). Acid-containing samples require a correction for acid content.
• Critical test conditions
  • Alkali solution: 0.1 N sodium hydroxide, 100 ml per test specimen.
  • Temperature control: water-bath at 65 ± 0.5 °C with stirring.
  • Exposure: typically 1 hour with gentle shaking at intervals.
  • Drying: ventilated oven at 105 ± 3 °C to constant mass before and after treatment.
• Sample preparation and pre‑extraction
  • Remove fat and vegetable matter by Soxhlet extraction with dichloromethane (1 hour, ~6 cycles/hour). Note: dichloromethane is toxic - use adequate ventilation.
• Apparatus and accuracy
  • Soxhlet extractor, thermostatic water-bath, 100 ml stoppered flasks, sintered-glass filtering crucibles (porosity 1), ventilated oven, analytical balance (accuracy 0.0002 g).
• Results
  • Report alkali solubility as percentage loss of dry mass (S). For samples with acid (pH < 4.0), determine acid content and report corrected solubility (S′) normalized to acid-free dry mass. Results and mean to three significant figures.

Applications and users

• Who uses it: textile test laboratories, wool processors, textile chemists, quality control teams, research institutions and certification bodies.
• Practical uses:
  • Assessing extent of chemical damage from bleaching, dyeing, or environmental exposure.
  • Comparing effects of different processing or finishing treatments.
  • Quality control during manufacture and evaluation of raw wool batches.
  • Research into fiber chemistry and durability.

Related standards

• ISO 1130 - Sampling for textile fibres (sampling guidance)
• ISO 3071 - Wool - Determination of pH of the aqueous extract
• ISO 3073 - Wool - Determination of acid content

Keywords: ISO 3072:1975, wool solubility in alkali, alkali solubility test, sodium hydroxide test, Soxhlet extraction, textile testing, wool quality control.