To make benzaldehyde in the laboratory, take 10 grams of benzene chloride, 8 gram lead nitrate and about 50 ml of water in a round flask. Attaches a reflux condenser to the flask. CO2 gas flows into the flask. So that the atmosphere of CO2 remains in the flask.
Heats the flask for about 6 hours in this condition. The mixture is then cooled and extracted by ether. Benzaldehyde enters the ether layer. Separating the ether layer and adding a saturated solution of sodium bisulfite(NaHSO3) to it.