Work out viscosity of a solution instantly with clear inputs, formula shown and shareable results.
A capillary viscometer measures flow times, and their ratio is the relative viscosity - no absolute calibration needed as long as densities are close. Subtracting one gives the specific viscosity, the fractional thickening caused by the solute, and dividing that by concentration gives the reduced viscosity. Extrapolating reduced viscosity to zero concentration yields intrinsic viscosity, which is how polymer molar mass is measured.
Relative and specific viscosity
eta(rel) = t / t0, eta(sp) = eta(rel) - 1
Reduced and inherent viscosity
eta(red) = eta(sp) / c, eta(inh) = ln(eta(rel)) / c
Because for dilute solutions the density ratio is within a fraction of a percent of one, and it cancels in the flow-time ratio.
Measure reduced viscosity at several concentrations and extrapolate the straight line back to zero concentration - the intercept is the intrinsic viscosity.