Gold on carbon oxidizes aldehydes to carboxylic acids in water solution under mild conditions without loss of activity on recycling, as does not occur for platinum on carbon. Also scarcely soluble aldehydes can be oxidized but the reaction rate is slower. Experiments carried out in an organic solvent such as CCl4 show a speed up of the reaction, in this solvent being recyclable both Au/C and Pt/C. Another explored possibility was represented by carrying out the reaction in the absence of solvent. However, for solid aldehydes like p- and o-OH-PhCHO the water solvent represent the unique alternative. (C) 2002 Elsevier Science B.V. All rights reserved.