New results in heat and mass transfer by convection Salvatore Rionero Department of Mathematics And Applications "R. Caccioppoli". University of Naples "Federico II". [email protected]. Accademia Nazionale dei Lincei, via della Lungara, 10. 00165 (Roma). [email protected] The heat and mass transfer in Navier-Stokes fluid layers, bounded by rigid planes, is investigated. The case of multi-component fluid mixtures is considered. Stability conditions in closed form, via hidden symmetry and skew-symmetries, are furnished.