The kinetics of electrochemical decarboxylation of fornlate ions has been studied in detail for the first time as a model reaction for examination of the decarboxylation and radical coupling that occurs with higher aliphatic acids. Current-potential curves have been obtained which show a sharp transition region, not diffusion controlled, which is characteristic of passivation phenomena. The behavior is observed with gold, palladium, platinum, and goldpalladiun~ alloys. Tafel slopes and exchange currents have been evaluated for the reaction and possible reaction mechanisms are examined in relation to the experimental results.Galvanostatic charging, reverse pulse discharging, and open-circuit decay transients hare been obtained which indicate formation of films of adsorbed intermediates on the surface. The transition regions in the current-potential curves are associated with formation of this ad-layer. The galvanostatic results enable distinctions to be made between some of the possible reaction mechanisms proposed and estimates to be made of the extent of film formation by adsorbed intermediates formed in the reaction. GESERAL INTRODUCTIONThe follo\virig iritroduction is intended t o cover material presented in this paper and in Parts I1 and 111.Despite the discovery by Kolbe many years ago (I) of a coupliilg reaction a t the anodic electrode during electrolysis of aliphatic carboxylic acids R.COOH t o give derivatives Rz and some oxidation by-products (Hofer-Aloest reaction), rather little is linown of the mechanism of this reaction froin a fundamental electrochemical point of view, e.g, with regard t o the primary anodic step (see ref. 2, p. 398). The reaction has been the subject of organic chemical studies for many years, including uses for chain extension of semiesters of dicarboxylic acids, dimerization of certain compounds, and other modifications of the reaction which have been adequately reviewed (2) in the literature of organic chemistry.111 this present series of papers , it is the aim to examine the basic electrochemical behavior of reactions involving anodic decarboxylation by choosing, initially, two systems in which side reactions are minimized, so that the electrochemical kinetics of a single reaction can be studied. In the first case we exanlirle the mechanism of the apparently simplest anodic decarboxylation that can occur, viz., that of formic acid or the formate ion. No other papers have evidently been published previously on the electrochemical kinetics of this reaction, and other work (e.g. ref.3) has been concerned only with the problem of coulombic yields of COz a t the anode, the absence of hydrogen as an anodic product, and the productio~l of hydrogen a t the cathode. This reaction is ideally suited for electrochemical study since ( a ) the reaction pathway is very largely the simple decarboxylation to give hydrogen ions and carbon dioxide, and (b) the reaction is an essential model reaction for studies on the Kolbe reaction itself. I t is also of interest in relation to the fue...
The recent invention of rechargeable "modified" manganese oxide materials paves the way to the development of secondary batteries suitable for numerous applications. This includes alternatives to primary dry cells, and secondary lead/ acid and nickel-cadmium batteries. Present results describe the performance of cells in which the modified materials are coupled with zinc and iron. As opposed to iron which does not affect the longevity and capacity retention of the modified electrodes, zinc has a pejorative effect on modified MnO2 materials, owing to the formation of hetaerolite at the positive electrode. Methods to alleviate this effect and produce viable modified MnO2/Zn systems are described. At present, these systems retain about 50% of their theoretical one-electron capacity even after two hundred fast charge-discharge cycles.
The heats of wetting by water of cotton cellulose containing various amounts of adsorbed and desorbed water were measured. These measurements together with those of the water vapor sorption isotherm were used to calculate the integral and differential enthalpies, free energies, and entropies of adsorption. Irreversible effects were avoided by vacuum-drying all samples a t room temperature. The dilfercntial enthalpy values suggest hydrogen bonding. The differential entropies are explained in terms of changes in both the adsorbate andThe surface area of the cellulose is calculated by applying the Brunauer-Em~nett-Teller and Harkins-Jura equations to the adsorption isotherm. The changes in the differential enthalpies and entropies of adsorption follow the same sequence as the changes in film formation given by the surface area calculations.No hysteresis was observed in the heats of wctting of adsorbed and desorbed samples. I t is concluded that the hysteresis of the sorption isotherm is an entropy phenomenon. This supports Barkas' explanation of hysteresis in terms of plastic deformation of a gel. INTRODUCTIONMeasurement of the amounts, the vapor pressures, and the energies involved when water vapor is added to and removed froin fibrous natural polyiners have made it possible to calculate in detail the therinodynamic properties of the systeins silk fibroin -water vapor and wool keratiil-water vapor (1, 2, 3). T h e present report includes the saine kind of ineasureinents on the system cellulose -water vapor.Wahba also made similar ineasuremellts on the cellulose -water vapor system (4). However, we believe that Wahba's drying procedures introduce a n irreversible effect. A similar but larger effect is sho\vi~ in the work of Argue and Maass ( 5 ) , who inade the first detailed measurements of the heats of wetting of cellulose by water.Babbitt (6) made a coinprehe~lsive a~lalysis of the adsorption isotherm of the cellulose -water vapor system and was the first to apply the Brunauer, Emmett, and Teller adsorptioil isotherin equatioil (7) t o this system. In the present work, surface area measurements have assisted us in interpreting the thermodynamic properties. E X P E R I M E N T A LCalori~netric measureinent of the heats of wettin:: by liquid water of cellulose equili--.
Passive and active acoustic measurements are effective and unique approaches to ocean observation. Both approaches have techniques that are well-established and suitable for immediate deployment as part of an operational observing system.Many of these techniques exploit the remarkable ability of lowfrequency sounds to traverse great distances in the ocean. Passive acoustic measurements of natural or man-made sounds are made for diverse purposes ranging from assessing the environmental impact of human activities, to geophysics, to monitoring changes in biodiversity in response to climate change. Active acoustic systems are employed for tracking instruments and acoustic tomography. Tomography has a role in the ocean observing system that is complementary to altimetry and profiling floats, particularly in the context of data assimilation and ocean modeling. Modest systems of acoustic receivers and sources deployed across ocean basins can make cost effective, sustained observations of a variety of ocean processes.
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