AbstractThe change of Huggins' constantk′ of the graft polymer solution brought about by varying the composition of the solvent was studied. The graft polymer solution studied was prepared according to the method described in the author's previous paper,(1)andk′ was obtained from viscosity measurements of the solvent with varying methanol contents. The following results were obtained:(1) The Huggings' constant was found to change with the variation in the methanol content of solvent.(2) The minimum value fork′ was attained when the solvent contained 75% methanol.(3) The first interaction coefficientsa2were determined and the critical point was also observed under the same condi