This document specifies a method, using dichloromethane, to determine the mass percentage of triacetate or polylactide, after removal of non-fibrous matter, in textiles made of mixtures of – triacetate or polylactide with – wool or other animal hair, silk, protein, cotton, viscose, cupro, modal,lyocell, polyamide, polyester, acrylic, elastomultiester, polypropylene, elastolefin, melamine, polypropylene/polyamide bicomponent,polyacrylate and glass fibres. Triacetate fibres which have been partially hydrolysed (i.e. saponification) cease to be completely soluble in the reagent. In such cases, this method is not applicable.