 Drying agents are used to remove trace amounts of water from an organic solution. Always use an Erlenmeyer flask, not a beaker. If a second layer (water) is seen in the flask, remove it by pipette before addition of the drying agent. Start by adding a small portion of drying agent (size of a pea) to the flask. Swirl the flask. Water will cause the drying agent to clump into particles larger than the original particle size, and possibly stick to the glass. A solution is dry when small particles the size of the original drying agent are notice with the flask is swirled. Add additional portions of drying agent until small particles are seen. Allow extra time when exposing a solution to anhydrous sodium sulfate $$\left( \ce{Na_2SO_4} \right)$$, as this drying agent takes some time. To remove the drying agent from the solution, decant (pour) the solution if using $$\ce{Na_2SO_4}$$, pellet $$\ce{CaCl_2}$$, or $$\ce{CaSO_4}$$. Remove the drying agent with gravity filtration if $$\ce{MgSO_4}$$ or granular $$\ce{CaCl_2}$$ are used. Rinse the drying agent with a few portions of fresh solvent, and combine the rinsings with the dried solution.