A study was made of physical and chemical changes that take place during bleaching of Rangeeni and Kusmi, the two main varieties of lac, by the improved hypochlorite bleaching process. The physical changes studied include life, flow and keeping quality. The chemical changes observed were oxidation, addition, substitution and partial hydrolysis. Fractionation and intrinsic viscosity, however, showed little overall molecular change.

The dielectric properties of shellac-incorporated natural rubber gum stocks were studied in the frequency range 100 Hz to 100 kHz and at different periods of curing. Incorporation of shellac in the gum stock resulted in decrease of the dielectric loss values of natural rubber. ZUSAMMENFASSUNG:Die dielektrischen Eigenschaften von schellack-enthaltendem Naturkautschuk wurden im Frequenzbereich von 100 Hz bis 100 kHz und bei unterschiedlicher HLtungsdauer untersucht. Das Einbringen von Schellack in den Gummi bewirkte eine Abnahme der dielektrischen Verlustwerte des Naturkautschuks.