In previous articles8 it was shown that difficulties inherent in the commutator rendered the commutator-potentiometer system undesirable for the measurement of overvoltage and transfer resistance. The present article is a description of a commutator oscillograph system which is much superior for such determinations.The moving coil oscillograph has been used by Reichinstein,4 *LeBlane,6 Lattery6 and Miller7 in studies of transient phenomena at electrode surfaces in electrolytes. In all these cases a source of intermittent direct current was used and the electrodes were connected directly to the oscillograph. The method was finally rejected because the oscillograph drew considerable current for its operation and thus changed the potentials of the electrodes under investigation while those potentials were being measured. This difficulty was partially overcome by Holler8 through the use of a vacuum tube amplifier. He used the new arrangement to study polarization and the nature of "transfer resistance" or as he called it "boundary resistance." His oscillograph required 150 milliamperes for full-scale deflection which made it necessary to use a three-tube amplifier. Even then it required 15 millivolts change in grid potential to produce a change of 1 milliampere through the oscillograph circuit; which means the arrangement is not suitable for accurate work.The cathode ray oscillograph has been adopted by Newbery9 for the study of polarisation and overvoltage. It is ideal in respect to its capacity to accurately follow extremely rapid changes of potential. Vibrations having a frequency of 106 per second may be recorded. It is also especially desirable in that it draws practically no current from the source. A marked disadvantage, however, is that it gives a deflection of only one millimeter per volt. By the use of an amplifier it is possible to secure deflection of one millimeter per 100 millivolts. Another very serious difficulty is that the

113) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.171.57.189 Downloaded on 2015-06-15 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.171.57.189 Downloaded on 2015-06-15 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.171.57.189 Downloaded on 2015-06-15 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.171.57.189 Downloaded on 2015-06-15 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.171.57.189 Downloaded on 2015-06-15 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.171.57.189 Downloaded on 2015-06-15 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.171.57.189 Downloaded on 2015-06-15 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.171.57.189 Downloaded on 2015-06-15 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.171.57.189 Downloaded on 2015-06-15 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.171.57.189 Downloaded on 2015-06-15 to IP POLARIZATION AND OVERVOI,TAGE. 137 K KI ( KI ( NI ( I Ki Ki KI Z H 19 J O J 53 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.171.57.189 Downloaded on 2015-06-15 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.171.57.189 Downloaded on 2015-06-15 to IP

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This paper is a continuation of studies on the platinized platinuln electrode in acid solutions saturated with hydrogen. The object was to secure information on the behavior of the electrode as current is passed through it. In all cases the solution was saturated with hydrogen. I)ata were obtained under four sets of conditions. (1) The electrode was cathodically polarized, then ilnmediately anodically polarized in a still solution.(2) The procedure was the same as (1) except the solution was stirred by a rapid stream of hydrogen. (3) The electrode was anodically polarized, then followed by cathodic polarization in a still solution. (4) The procednre was the same as (3) except the solution was stirred by a rapid stream of hydrogen. The results all support the proposition sublnitted in previous papers that the electrode phenolnena below, at, and above the so-called reversible value are all the salne; and that the potential of the electrode under any of these conditions is deterlnined by the activity of hydrogen atoms and hydrogen ions at the electrode-solution interface and could be calculated by the regular Nernst equation provided these activities were known. A corollary of the theory is, of course, that hydrogen ions may be discharged at potentials more positive than the so-called reversible value; also that the activity of the hydrogen atoms, and thus the potential, depends largely upoll the material and physical condition of the electrode.