This document specifies a method, using xylene, to determine the mass percentage of polypropylene, after removal of non-fibrous matter, in textiles made of mixtures of — polypropylene fibres with — wool, animal hair, silk, cotton, viscose, cupro, modal, lyocell, acetate, triacetate, polyamide, polyester, acrylic, glass fibres, elastomultiester, melamine and polyacrylate.