Generally the surfaces of Al and Al alloys are covered with the films of Al oxide. So that, the chemical and physical properties on the surface of Al are subject to the states of the films of Al oxide. For that reason, the exact determination of the electrochemical and chemical properties of Al is very difficult, Usually the examination of the state of Al with the film of oxide, is more important than that of the properties of Al without the film of the oxide. It is very difficult to exactly measure the standard electrode-potentials of Al. The data of the potentials of Al which were measured by many people, are as follows:Neumann measured in some electrolytes be overved the next datas.-1.13 volt in Al sulfate solution-1.29 volt in Al chloride solution-1.05 volt in Al nitrate solutionLatimer and Green felder calculated fromthe elec trode potential of Al and obtained-1.69±0.01 volt at 25°CSimilary Kistialscrosky -1.32 voltProssbacle -1.33 voltWilsmore -0.9 voltHeyrovsky -1.33 voltMiller and Hulzl used many solution abd measured the electrode-potentials of Al which scraped the Film of oxide off the surface of Al.Allender measured the potential between Al and Pt electrode in the NaCl solution. He examined the properties of samples which carried out mechanical treatments, or the influences of heat rreatments. Sato measured the electrode-potential of Al film (positive electrode) which used in electrolysis as accumulator Igarashi and Kodama measured electrolytic solutionaltension of 99.99%Al in hyrogen atomosphere. The results are give in in their paper that the potentials of improving. sampales risen as soon as it is steeped in the solutions and approached to the constant value, but the potentials of annealing sample continued to rise, repeating descent and rise, and gradually approached to the constant value. R. Ergang measured potential of Al in the NaCl solution, i. e. the late of potential are following;-99.95% Al -0.85 volt99% Al -0.83 voltExperimentalWe measured the potential of Al with vaccum tube potention meter which is newly originated. The character of the apparatus is the use of vaccum tube 6c6. When two tubes is connected In the circuit of bridge and put unknown electrode milli the solution, the equilibrium state to brolsen off. The differluce of potential is measured by milli voltmeter, connecting circuit, milli-voltmeter is used 45 m. v. pyrometer and sensibility of the millivoltmeter is regulrated by resistance box, connecting paralel in circuit. In the adjustment of potentiometer, we used the Westarn Standard cell and measured the milli-volt, kupping constant electric pressureWhen the electrode is dipped in the electrolyte, the equilibrium state is distructed, We measured it by milli-voltmzter. The measurement of potential were used by the conbined cell, i. e. Single electrode cell (Al were dipped in 3%NaCl+0.1H2O2, 0.1%HCL, 0.5%H2SO4) is combined with the standard calomel electrode cell, (Sat. Hg CL cells), by liquid.In this way a complete cell were constructed by measuring metal electrode and standard electrode. The potential between two electrodes, were measured by newly originated vaccum tube potentiometer.Results1. The potential is similar inclined to electro-positive.2. The potential is chanted by the purity of Al. The more purity is high, the more potential is high.3. The potential is changed by the degree of improvement of samples.4. The potential is changed by the heat treatment of sample.