We have studied, as a function of temperature and scattering angle, the intensity and time dependence of light scattered by the three-component liquid mixture, bromobenzene-water-acetone, both above and below its critical mixing temperature Tc. This system can be pictured as a highly impure binary system, with acetone playing the role of an inert impurity. The concentration of acetone in the mixture was about 57 wt %. Both above and below Tc, the decay rate of intensity fluctuations in the scattered light is well described by the Kawasaki theory. The critical exponents and ratios appear to show renormalization due to the presence of the impurity, as predicted by Fisher and Scesney