The latent heat is still present , and is responsible for slowing the temperature rise, but its presence is not nearly as obvious as when we had only pure water. The temperature is rising because the liquid phase is being enriched in water , which has a higher boiling point. This liquid enrichment occurs because the first vapors were mainly ethanol, and so a larger fraction of water was left behind. The last drop of liquid is very rich in water , and it too eventually boils away. The temperature of the vapors within the pot continues to rise until they are as hot as the burner.
Mixtures boil when they reach a temperature called their bubble point .
Afterwards the temperature slowly rises, even though latent heat is still present, until the last drop of liquid vaporizes at the dew point . Once all the liquid is boiled off the temperature of the vapor mixture will again increase . It is fairly easy to turn pots and burners into a batch distillation apparatus. A tall column is also desirable because it greatly improves the separation by giving high boiling compounds another chance to condense before they reached the top and are collected. Finally, by using different collection vessels , the original mixture can be separated into fractions .