The synthesis of benzoin proceeds as follows.

and the following procedure is performed:

A solution of sodium cyanide (1.1 g, 0.02 mol) in water (10 mL) was added to a stirred solution of benzaldehyde (10.6 g, 0.1 mol) in 15 mL ethanol. The reaction mixture was refiuxed gently for half an hour and cooled in an ice bath. The precipitated product was filtered, washed with cold water, dried well and crystallized from ethanol to afford 9.0 g (85.0%) of benzoin.

1. indicate what by-products or impurities are removed by filtration

2. indicate what by-products or impurities are removed   in the recrystallization from ethanol

3. Why is the reaction mixture placed in an ice bath?

4. How can the product be dried? What methodology can be used?