A method and apparatus to aid the loading and unloading of flexographic plates to and from an imager. Optionally, the reactants are combined with an acid to lower the pH of the reaction solution wherein the lowering of the pH optimizes the yield of the desired N-substituted phthalimide product. A container-present indication indicating one of the containers is positioned so that its RFID tag is in the antenna range is received. The second increase rate is smaller than the first increase rate.