We wish to investigate the pH-dependence of the strong interfacial interaction of 1,2-Dimyristoyl-sn-glycero-3-phosphocholine (DMPC) with poly(silicic) acid at the air-water interface. Our recent X-ray studies of proteins shows such a strong pH dependence and experiments with X-ray reflectivity at the air-water interface show that an even stronger occurs with 1,2-Diacyl-sn-glycero-3-phosphocholine (PC). In order to probe at higher resolution the interaction of the lipid with the silicate, we propose to use three deuterated versions of DMPC, and to combine the neutron data with our X-ray work