This document specifies a method, using acetone, to determine the mass percentage of acetate, after removal of non-fibrous matter, in textiles made of mixtures of — acetate with — wool, animal hair, silk, regenerated protein, cotton (scoured, kiered, or bleached), flax (or linen), hemp, jute, abaca, alfa, coir, broom, ramie, cupro, viscose, modal, polyamide, polyester, acrylic, elastolefin, elastomultiester, melamine, polypropylene/polyamide bicomponent, polyacrylate and glass fibres. It is not applicable to mixtures containing modacrylic fibres, nor to mixtures containing acetate fibres that have been deacetylated on the surface.