CdS-silica xerogel composites were prepared from tetramethoxysilane, acidic water, and formamide mixtures homogenized by high power ultrasounds. Different concentrations of Cd(NO3)2 were added. CdS semiconductor nanoparticles were precipitated by H2S gas diffusion through the sonogel porous structure. Composite mechanical properties were enhanced by an impregnation process by the gel soaking in the same sol as-prepared. Textural parameters evolution is compared to the salt content in order to find the best performance to CdS nanocrystal growth. The impregnation process allows a better composite protection.