Hall coefficient for CuSO4liquid electrolyte has been measured and found to be positive. Detection of Hall signal was limited to de methods although ac techniques were also investigated. The Hall coefficient increases with decreasing concentration of solute and for distilled water approaches 5 × 105cm3/coul. Calculations of H+ion mobility using the two carrier expression for Hall coefficient show the charge carrier in a liquid electrolyte to be the H+ion. Mobility of the proton in water is of the order of 1 cm2voltsec, which is near the value in ice