PURPOSE: To show the behavior of a binary fluid as it passes through the critical temperature.

DESCRIPTION: A small sealed vial contains the correct mixture of aniline and cyclohexane to form a binary fluid when heated above its critical point, about 95 degrees Fahrenheit. The fluid is heated by hand or using a beaker of warm water. Then the vial is placed in the laser beam. When the fluid cools down to its critical point it breaks into cells, becoming cloudy, and scatters the laser beam chaotically. This is very dramatic because it happens very quickly.

SUGGESTIONS: DANGER: Do not break or open vial.

REFERENCES: (PIRA 4C50.15) See Demonstration Reference File for information on this binary fluid and other reference articles.

EQUIPMENT: Vial of aniline/cyclohexane binary fluid, warm water beaker, and laser with screen.

SETUP TIME: 5 min.

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