Interferometric studies of the growth of stearic acid crystals and their optical properties

Abstract

On the basal planes of stearic acid crystals, grown from solution, growth spirals observed by optical and phase contrast microscopic techniques are reported. These growth spirals are in accordance with the theory of Burton, Cabrera and Frank. For the measurement of spiral step-heights multiple-beam interference methods were used, including a modified multiple-beam interference method, which is described. The minimum step-height found was 46.3 ± 0.8 Å , which agrees with the x-ray repeat unit. In addition, step-heights which were integral, as well as half integral, multiples of this unit were found. By interferometric methods the refractive index was found to be 1.42 ± 0.04 and for the two types of crystal rhomb observed the birefringence for directions of vibration parallel to the `a' and `b' axes was approximately 0.018 and 0.015 respectively for λ = 5461 Å .