The reactions of butyronitrile were investigated in high-temperature water at 330 degrees C and various pressures ranging from 128 to 2600 bar. Residence times ranged from 5 to 180 min. The product spectrum included butanamide, butyric acid and ammonia; gas formation was negligible. A four-step autocatalytic rate model, incorporating the product acid as the catalytic species fitted the data well. This allowed the estimation of apparent activation volumes for each of the reaction steps. These were in turn decomposed into electrostatic and non-electrostatic contributions. At the lowest pressure studied (128 bar), the electrostatic activation volume Delta V-es(not equal) was twice as large as the hydrostatic activation volume Delta V-hs(not equal). These activation volumes were comparable in value at all other pressures studied.