In this work we synthesized catalytic solids by digesting freshly prepared magnesium orthophosphate with a saturated solution of alkali carbonates. The solids thus formed were mixed orthophosphates of structure X MgPO4 (X = Li, Na, K) that were characterized by X-ray diffraction and diffuse reflectance IR spectroscopy. Ali of them exhibited a high activity and selectivity in the conversion of primary and secondary alcohols into their corresponding carbonyl compounds. Their activity and selectivity are compared with that of X MgPO4 orthophosphates (X = Li, Na, K) obtained from a dry phase.