Abstract
By studying the molecular weights of various solutions of cis‐1,4‐polyisoprene the authors arrived at the formula \documentclass{article}\pagestyle{empty}$$\left[ \eta \right] = \sqrt {2/c} \sqrt {\eta _{sp} - {\rm l}n\eta } _{rel} $$ which allowed the calculation of the intrinsic viscosity of the polymer solutions by a single viscosity determination. The formula was verified for different systems of polymer–solvent and the values are in accord with those obtained by extrapolation. An operating concentration of about 0.2% is recommended.