Gelatin Light-scattering, by a New Enzymic Digestion Technique

IN applying light-scattering techniques to molecular-weight and dissymmetry measurements for gelatin fractions in solution, serious doubts arose concerning the efficiency of the usual clarification methods (ultrafiltration, high-speed centrifugation). A convincing check of clarifying processes existed only for fractions of low molecular weight, where the experimental value of the dissymmetry, Z , should approximate to the theoretical value, unity, if all suspended impurities have been removed. For higher molecular weights, a solution free from impurities would be expected to give Z greater than 1, and the procedure adopted by other workers has been to repeat the clarification until Z became constant. It was suspected that this limit did not correspond with complete clarification, and that the use of this criterion caused significant errors in the 90° scatter (and M w ) and large errors in the values of Z .