Extrapolation procedures for intrinsic viscosity and for Huggins constant k′

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Abstract
Conventional extrapolation procedures for the calculation of intrinsic viscosities and the Huggins constant k′ have been critically examined. A condition which must be satisfied by the basic equation for viscosity–concentration relations of dilute solutions of nonelectrolytic polymers has been clarified. On the basis of the comparison of the curvatures for empirical equations and for the basic equation, it is proposed to use arithmetic averages of the values calculated from a Huggins plot and those from a Martin plot for good‐solvent systems, and to employ the averages of values from the former and those from a Schulz‐Blaschke plot for poor‐solvent systems as approximations to the correct values. Failure to confine approximations in the usual statistical treatment of experimental points to the given range of the variables as well as neglect of the fact that curvatures for the empirical and basic equations do not necessarily coincide are the usual sources of error in the conventional extrapolation procedures.