This part of ISO 1833 specifies a method, using formic acid, to determine the mass percentage of polyamide fibre, after removal of non-fibrous matter, in textiles made of mixtures of polyamide with - cotton, viscose, cupro, modal, lyocell, polyester, polypropylene, chlorofibre, acrylic, glass fibre, elastomultiester,elastolefin and melamine or wool or animal hair fibres with the following restriction: when the wool content exceeds 25 %, the method described in ISO 1833-4 shall be used.