In this paper we consider feedback passive systems, defined as nonlinear systems that can be rendered (strictly) passive by means of state feedback. For feedback passive systems in a parametric normal form, we present an adaptive controller that effectively 'passifies' the system. The proposed control uses techniques of Speed-Gradient (S-G) methodology from the Russian literature. Stability results can be given which do not require the plant to be linear in the parameters. Moreover, examples indicate that the S-G approach has several good features such as avoiding overparametrization, preserving physical structure and improving the speed of convergence.