Sets out a method for the quantitative analysis of binary mixtures of chlorofibres (homopolymers of vinyl chloride) and certain other fibres using concentrated sulfuric acid as a solvent for the constituent other than chlorofibre. This Standard may be used in place of AS 2001.7.11 and AS 2001.7.12 in all cases where a preliminary test shows that the chlorofibres do not dissolve completely either in dimethylformamide or in the azeotropic mixture of carbon disulfide and acetone.