In this work we deal with robust control of a class of first-order nonlinear systems which contain uncertainties. To cope with the uncertainties, an observer-based controller is proposed, and the uniform boundedness of all closed-loop signals and semiglobal practical convergence of the system state are guaranteed. In contrast with some previous attempts to relax the a priori knowledge on uncertainties bounds by using discontinuous control law, we propose a dynamic compensator which leads to continuous control laws. The applicability of the control scheme to regulation of temperature in stirred tanks and one-point control in distillation is shown by numerical simulations.