Abstract
The molecular weight averages of narrow and broad distribution polyethylene have been determined by controlled precipitation from a mixed solvent of xylene/n‐hexanol in the temperature range 433 to 33K. Estimates of the distribution (D) which compared unfavourably with and considerably under‐estimated those determined by gel permeation chromatography (g.p.c.) were obtained by a calibration procedure between the temperature of initial onset of precipitation and the weight average molecular weight which have been used previously ~1,2~ to characterise turbidimetric curves. However, the calibration curves gave an accurate estimate of the weight average molecular weight. There was also an accurate correlation between the reciprocal of the breadth of the turbidity‐temperature curves as measured by 1/T~max~ (dτ/dT) ^−1^ i.e. (S)^−1^, and the logarithm of the g.p.c. dispersity which enabled the breadth of distribution to be determined. With these two correlations molecular weight characteristics could be determined rapidly which compared favourably with g.p.c. data. The method has been applied to fractions obtained for 3 methods of fractionating polyethylene in order to compare their relative efficiencies.