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