Why is it necessary to filter off drying agents before distillation?

Question

anhydrous magnesium sulfate or anhydrous calcium chloride are examples of drying agents which remove from water reversibly.

Answer 1

For one, the drying agents are there so that you can remove the water before the distillation.  In some cases it would not be necessary but it makes the distillation simpler.  Also, the heat of the distillation process could release some of the water, initiate a chemical reaction, decompose the drying agent, or interfere in another manner.  Basically, filtering out the solids makes the distillation more efficient and less likely to create any complications.