According to the query of Renren Library, benzoin condensation reaction will go through the process of clarification, turbidity and clarification during heating reflux, because benzaldehyde used in the reaction will volatilize during heating and ethanol is needed as the solvent for the reaction. The specific process is as follows:

1. At the beginning of the reaction, the solution was clear. After heating, benzaldehyde gradually volatilizes, and the solid matter in the reaction system gradually decreases, so the solution gradually becomes turbid.

2. The reason of turbidity is that the volatilization of benzaldehyde and the small molecular organic matter produced by the reaction make the solution unstable and turbid.

3. When benzaldehyde volatilizes completely, the solid substance in the reaction system disappears completely, and the solution becomes clear again. At this time, the benzoin condensation reaction produced the product, the condensate of ethanol and benzoin, so the solution became clear.