Organic Chemistry Lab: Recrystallization

Turn on the hot plate with water as the recrystallization solvent. Heat the water until it reaches near-boiling temperature with visible condensation, without allowing a vigorous boil. This allows controlled heating and prevents bumping.

Using a powder funnel, carefully pour the two nitrobenzoic acid solid sample into a clean Erlenmeyer flask. The wider funnel opening prevents spillage during transfer.

Transfer approximately 2 mL of hot water to the Erlenmeyer flask using a transfer pipette, just enough to cover the solid. Insert a wooden boiling stick to prevent bumping, then place the flask on the hot plate and heat gently until boiling begins.

Continue adding hot water in approximately 1 mL portions while swirling the flask, until all cloudiness disappears and a clear brown solution forms. The compound will dissolve completely only at elevated temperature, indicating proper solvent selection.

Add one final milliliter of hot solvent to account for evaporation during heating. Remove the flask from the hot plate and boiling stick, then place it on the countertop to cool slowly at room temperature.

Wait for crystals to form as the solution cools slowly, ideally over 10-20 minutes. Slower crystal formation results in purer product with better purity, as impurities are excluded during gradual crystallization.

Place the Erlenmeyer flask in an ice bath for approximately 5 minutes to complete crystallization. After cooling, recover the purified crystals using vacuum filtration.