Evaluation of the Intrinsic Viscosity

Series expansion of the natural logarithm demonstrates the equivalence of this definition to Eq. (50). It follows also from Eq. (51) that 

In practice it is customary to measure the relative viscosity at two or more concentrations so chosen as to give relative viscosities in the range from about 1.10 to 1.50. Either tjsp/c or (In nr)/c (or both) is extrapolated graphically to c = 0. 

If the intrinsic viscosity is large (i.e., greater than about 4 deciliters per gram), the viscosity is likely to be appreciably dependent on the rate of shear in the range of operation of the usual capillary viscometer. Measurements in a viscometer permitting operation at a series of rates of shear extending to very low rates are then required in order to extrapolate nsp/c to its limiting value at a shear rate of zero. Extrapolation to infinite dilution does not eliminate the effect on this ratio of a dependence on shear rate. 

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When both the hydrodynamical interactions and the excluded volume effects are present the evaluation of the intrinsic viscosity becomes much involved because we n l the quantity... 

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