Dipole and multipolar contributions are included in measurements of the differential capacitance of electrolyte:oxide:semiconductor devices, as well as XPS signals from silica colloidal jets. Both methods produce pH-dependent total interfacial potentials for the silica:water interface at various [salt] that agree well with our recently published HD-SHG-derived total potentials. We therefore conclude that measurements of the SHG amplitude and phase provide the total interfacial potential drop across the oxide:water interface. It contains the Coulomb, dipole, quadrupole, and all other contributions, 𝛷(0) $ , to the interfacial potential drop, and is quantified from the measured SHG amplitude, Esig, and phase, jsig, for a given DC phase angle, jDC, according to 𝛷(0