Estimation of heat of dilution of polymer solution: a trial on a correction of the heat of stirring ascribed to the viscosity difference before and after dilution

The heat of dilution for the polystyrene and methyl ethyl ketone system was measured using an isothermal calorimeter, and the heat correction due to the change of stirring before and after dilution was estimated from the observed change in heat of dilution. The net heat of dilution of the polystyrene and methyl ethyl ketone system obtained was very small and the system was considered to be almost athermal. The heat correction due to the change of stirring was unexpectedly large, and often exceeded the net heat of dilution. The interaction parameters obtained for the polystyrene and methyl ethyl ketone system were +0·035, +0·012, ?0·022, and ?0·062 for molecular weights of 2100, 22 000, 57 500, and 212 000, respectively, at 298·15K.