1. A bulk composition of X cools to the liquidus, at which point An crystallizes.
2. Continued crystallization of An causes liquid composition to move toward Di.
3. When T=1274
°C, liquid has moved to eutectic; Di begins to crystallize. No
change in temperature or composition of any of the 3 phases is permitted until
the liquid has completely crystallized.
4. At temperatures below 1274°C, only crystals of An and Di are present.