When fiber assemblies, e.g., yarns and fabrics, are washed, substances to be removed migrate through water and fibers in fiber assemblies. In such processes, the coefficient of diffusion of the substance in water is remarkably different from that in fibers. In the previous papers, an assumption was made that the fibers can be regarded as columns and fiber assemblies as planes or columns to analyze the process of substance migration in fibers and water. Theoretical equations had been derived on the basis of the diffusion theory and the validity of these equations had been confirmed by the washing experiment of polyvinylalcohol.
This paper deals with the washing experiment by using cotton-and polyester-fabrics, much different in their properties. Sodiumhydroxide and acidic dyestuff, much different in their molecular size and diffusional behaviour are selected as the substances to be removed . The experimental values have been compared with the theoretical values. Results of washing experiment in stirred water have closely agreed with the calculated values by the theoretical equations derived by regarding fiber assembly as a column.

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