Dears members & peers, In Note 4 of the standard test method ASTM D3230 (Standard Test Method for Salts in Crude Oil - Electrometric Method) is established that the 10:20:70 (Ca, Mg, Na) proportions are representative of the chlorides present in a number of common crude oils. When the relative proportions of calcium, magnesium, and sodium chlorides are unknown for a given crude oil (e.g.: non-conventional crude oils such as extra-heavy crude oils)... Is still valid to use a calibration curve whose standard salts are mixed in a 10: 20: 70 ratio?. Thanks...