This document specifies a method, using xylene, to determine the percentage of polypropylene, after removal of non-fibrous matter, in textiles made of binary 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.