ISO 2913:1975 PDF

Overview - ISO 2913:1975 (Wool - colorimetric determination of cystine + cysteine in hydrolysates)

ISO 2913:1975 defines a laboratory colorimetric method for determining the combined content of cystine and cysteine in wool hydrolysates. It is the first edition (1975) produced by ISO/TC 38 (Textiles). The method is applicable to all‑wool textiles in any form (loose fibre, sliver/roving, yarn or cloth) provided the wool has not been oxidized or reduced. Dyes and certain metal‑complexing agents can interfere with the colorimetric measurement.

Key topics and technical requirements

• Principle: reductive fission of disulphide bonds with sodium disulphite, followed by color development with dodecatungstophosphoric (tungstophosphoric) acid; absorbance of the blue complex measured spectrophotometrically.
• Reagents called out: approx. 6 N sulphuric acid (for hydrolysis), acetate buffer pH 5.6, tungstophosphoric acid reagent, sodium disulphite, and a cystine standard solution.
• Hydrolysis: wool hydrolysis in aqueous sulphuric acid at elevated temperature (oven) for the prescribed time, then dilution and filtration to prepare the hydrolysate.
• Optical measurement: absorbance read between 720–890 nm (preferably 720 nm) using 10 mm cells; measured values should be