This part of ISO 1833 specifies a method, using cyclohexanone, to determine the percentage of chlorofibre, modacrylic, elastane, acetate and triacetate, after removal of non-fibrous matter, in textiles made of mixtures of acetate, triacetate, chlorofibre, certain modacrylics, certain elastanes with wool, animal hair, silk, cotton, cupro, modal, viscose, lyocell, polyamide, acrylic, melamine, polyacrylate and glass fibre. Where modacrylics or elastanes are present, a preliminary test should be carried out to determine whether the fibre is completely soluble in the reagent. It is also possible to analyse mixtures containing chlorofibres by using the test methods described in ISO 1833-13 or ISO 1833-17.