Abstract: In a process for the preparation of acetone cyanohydrin by the reaction of acetone and hydrocyanic acid in the presence of a sodium hydroxide catalyst, the method of removal of corrosion inducing sodium ion during the purification of the crude acetone cyanohydrin, involving the steps of (1) passing a cooled crude acetone cyanohydrin feedstream through a cationic ion exchange resin to remove substantially all of the sodium ion; (2) regenerating exhausted ion exchange resin; (3) acidifying the substantially sodium ion-free crude feedstream to a pH of 1.5-2.0 to stabilize said crude acetone cyanohydrin; (4) feeding the acidified substantially sodium ion-free crude feedstream to a first concentrator; (5) removing overhead, from the first concentrator, unreacted acetone and sending the bottoms from said first concentrator to a second concentrator; and (6) removing purified acetone cyanohydrin as bottoms from the second concentrator and recycling the overhead for further generation of acetone cyanohydrin.