An experimental application of RNCL to pH control is presented. The experimental setup consists of a computer controlled CSTR (continuous stirred tank reactor) and the control objective is to maintain the pH of a strong-acid strong-base system at the neutralization point in the presence of disturbances. The algorithms considered are PI (proportional-integral) control, nonlinear IMC (internal model control), and RNCL (robust nonlinear control law). The experimental results point to the excellent capability of RNCL for controlling pH in comparison to nonlinear IMC and PI control.