Benzoic acid is a common preservative, while sodium chloride is one of humankind's most ancient and popular seasonings. You can separate a mixture of these two compounds by exploiting the difference in solubility. Benzoic acid is poorly soluble in cold water, while sodium chloride dissolves well in water even at cold temperatures. Many high school or college intro labs involve an experiment of this kind to teach students how to separate components of a mixture.
Transfer the sample of benzoic acid and sodium chloride to one of the 250ml beakers.
Add 75ml of water.
Stir the mixture to dissolve the salt.
Prepare an ice water bath in the 1-liter beaker. Place the 250ml beaker in the ice water bath, but without allowing it to tip over or take in water from the ice bath. Continue to stir the mixture.
Place a piece of filter paper in the funnel, and dampen it slightly so it adheres to the funnel. Place the empty 250ml beaker beneath it, and pour the mixture through the filter paper in the funnel. The benzoic acid, which did not dissolve, will remain in the filter paper, while the sodium chloride solution will pass through.