‘Viscacelle’ as a Material for making Compensating Plates and Wedges for the Polarising Microscope

Abstract

VISCACELLE (cellulose sheet manufactured by Messrs. Courtaulds by the viscose process and used extensively as a wrapping material) is birefringent. There seems little doubt that this property is due to a net orientation of the long cellulose molecules caused by the unidirectional tension to which the sheet is subjected while being spun. Under this tension, the molecules may be expected to arrange themselves so that their length directions are parallel or nearly parallel to the direction of tension. This explanation is supported by the fact that the direction of tension (revealed on cut sheets by parallel streaks) is the slow direction of vibration.