サクシノニトリル-カンファー系の平衡状態図

Abstract

Transparent organic compounds with a low entropy of fusion have been widely used for in-situ observations of solidification phenomena. The succinonitrile-camphor system is one of such systems.This paper presents the equilibrium phase diagram of succinonitile-camphor alloy saturated with 1.013×105 Pa argon. Base materials were purified by distillation and by zone refining and then mixed under argon atmosphere. Then the alloys were introduced into a small glass cell and sealed tightly with epoxy resin. This glass cell was then put on the hot stage and observed with an optical microscope. The liquidus temperature was defined as the temperature where a small crystal did not grow nor melt. The eutectic temperature was measured by differential thermal analysis. The alloys were also introduced into the glass cell, incorporating a calibrated fine thermocouple. The glass cell was put on the temperature gradient stage and driven unidirectionally with a very slow velocity. Then, the solidus temperature was defined as the solid/liquid interface temperature with planar solidification. The liquidus and solidus lines in the hypo-eutectic region were found to be straight. The liquidus slope is −0.90 K/mass% and the equilibrium distribution coefficient of succinonitrile is 0.33. The latter agrees quite well with the thermodynamically calculated value. The eutectic temperature was found to decrease with increasing camphor content. Strictly speaking, this phase diagram is a part of the ternary system. Thus, due to the different effect of argon on succinonitrile and that on camphor, the eutectic temperature varies with camphor content. The eutectic point is 26.6 mass% camphor and 306.0 K.