Phase Diagrams

· The photograph represents the effects of a multi-zone pass. The sample is napthalene containing a red dye. The wire loops are the heaters that form the melt zone, the brass rings are cooled and solidify the sample before it is passed to the next zone.
· The cylinder and sample are moved to the left at about 2 cm/hour, sweeping the molten zone to the right. After moving one heater spacing at this speed it jumps back to its initial position and starts again.
· Each reset is equivalent to another zone pass for each molten region.

From: Pfann, Zone Refining, Scientific American 217 (1967) 63