Take 0.020 moles of sodium hydroxide pellets in an Erlenmeyer flask of 125 ml capacity. Add 4 ml of water to dissolve the sodium hydroxide and wait for the solution to cool.
Weigh 0.0160 moles of benzaldehyde and 0.0080 moles of acetone into another Erlenmeyer flask. To this, add 10 ml of a 95 percent ethanol solution and mix. Pour this solution into the flask containing sodium hydroxide solution and mix with occasional swirling. Watch for the formation of a yellow precipitate in about 15 minutes.
Filter the precipitate using vacuum until all the liquid is removed from the residue and wash it with 10 ml of water. Disconnect from the vacuum line, wait for a minute and again connect to the vacuum line. Wash the residue with 2 to 3 ml of an ice-cold 95 percent solution of ethanol.
Weigh the residue. Calculate the amount of ethyl acetate you will require for re-crystallization if you use 2.5 ml for every gram of the product.
Place the solid residue into a fresh Erlenmeyer flask and add half the quantity of ethyl acetate. Mix and heat until the suspension begins to boil. Gradually add 1 ml portions of ethyl acetate, allowing the suspension to boil between additions. Repeat this as many times as necessary until the suspension changes into a clear solution.
Remove the solution from the hot plate allow it to attain room temperature. Place the solution into an ice bath and observe the formation of pure dibenzyl acetone solid. Collect the compound by filtering through a Buchner funnel.