Rhodium,
Here is another ref to add concerning synthesis of Diphenylacetonitrile: US Patent 2,443,246
A superior alternative to the method they use to make the mandelonitrile follows: To a 40 degree C solution of 40 g NaHSO3 and 250 mL water 34 g benzaldehyde (0.324 mol) is added with vigorous stirring. After 20 minutes cool the reaction mixture down to 0 degrees, add 200 mL Ether and drip in a solution of 17 g NaCN in 70 mL water. Agitate for 30 minutes at 0 degrees, then seperate the organic phase and extract the aqueous phase twice with 50 mL portions of ether(or toluene). The combined ether extracts are washed with 2 x 100ml conc. NaHSO3 solution to remove traces of unreacted benzaldehyde(dont skip this step), washed 1 x 50ml brine then dried over anhydrous calcium chloride. After rotovaping the solvent under a vacuum, the remaining oil is allowed to solidify upon cooling then placed in the vacuum dessicator to remove last traces of water. Yield is very high and mandelonitrile produced using this method is ideal for use in the Friedel-Crafts reaction described in the patent.
I dont have a ref for this procedure, it is based on a ref someone posted for synth of p-methoxymandelonitrile. It has been run 3 times and works as described.