The Effect on Wool of Boiling in Aqueous Solutions I‐Solutions at pH 1.5–9 with and without Sodium Sulphate

Abstract

Wool of 64s quality, in the form of yarn and cloth, has been given boiling treatments of 3 hr. with 50 min. for raising to the boil to imitate prolonged commercial dyeing processes but without the addition of dye. The pH of the solutions has been controlled at selected pH values between 1.5 and 9 by the gradual addition of sulphuric acid or sodium carbonate during the boiling. The wool has subsequently been examined for modification by means of determinations of alkali solubility, soluble nitrogen, disulphido sulphur, total sulphur, breaking load air‐dry and wetted with water, extension at break, abrasion resistance, and loss in weight. A smaller quantity of 56s Corriedale wool has been treated concurrently though subjected to fewer tests. The conclusions reached are‐ (1) the wools have suffered minimum modification when boiled at pH 3–3.5; (2) sodium sulphate, in concentrations up to 9.2 g./litre, has shown relatively little effect on the wool within the pH range 1.7–6.8, but above pH 6.8 the presence of sodium sulphate has caused alkali damage, which increases rapidly with increase of salt concentration and rise of pH; (3) a strong correlation has been found between disulphidê content and wet breaking load for treatments having pH values above 4; a similar correlation has been found to apply to abrasion resistance after about 20% of the original disulphide sulphur has been broken down; (4) alkali solubility and soluble nitrogen have shown a strong correlation with abrasion resistance and to a lesser extent with wet strength for treatments having pH values below 2.5. The practical implications are discussed.