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An EMS study of the adsorbable and electrooxidizable impurities in our electrochemical system was undertaken. The source of most of the impurities was found and corrected. The adsorbtion and oxidative desorbtion of methylcyclohexane and isobutane was studied. Steady state and time dependent results are presented. A new digital data acquisition and experimental control system was developed and interfaced to the EMS system. This system made possible the acquisition of much more useful data from a single experiment rather than depending upon very high reproducibility between experiments., See also report dated Dec 73, AD-A009 017.

Elucidation of the mechanism of propane electrooxidation on platinum is complicated by the presence of several partially oxidized carbonaceous adsorbates. In this work techniques of 'Electrochemical Mass Spectrometry' (EMS) have been developed and applied to simplify analytical characterization of species present at the propane anode. EMS is based on interfacing a non-wetting porous electrode to the inlet system of a mass spectrometer. The preparation of a suitable porous electrode is described. Transport across the gas-liquid interface is characterized using a rotating porous disk. A diffusion model is developed for the porous electrode. Steady state and nonsteady state collection phenomena are investigated. A novel technique for the determination of diffusion coefficients is presented. Labelled carbon studies were carried out using propane-2-13C. Observations on the open circuit behavior of the propane anode are included., See also report dated Dec 73, AD/A-006 550.

A theoretical analysis of the porous electrode used in previous propane oxidation studies was undertaken. The model transport through the porous platinum layer, porous Teflon membrane and the fritted glass support on the vacuum side of the interface is discussed. The model was tested experimentally using rotating porous electrodes, with and without a porous platinum layer. Experiments were performed at open circuit and at constant applied potential with and without a vacuum behind the glass frit of the electrode. The experimental results are consistent with the postulate of a solution diffusion layer existing adjacent to the porous metal, a porous metal layer filled with solution and a porous Teflon barrier containing pores largely unfilled with solution. In testing the model for the porous electrode using a rotating porous Teflon disk electrode, a new method for determining the diffusion coefficient of gases in water was devised and applied to argon and helium., See also report dated Jun 73, AD-780 947.

The report is the fourth in a series dealing with propane electrooxidation on platinum at 100C in 12M H3PO4 using the technique of Electrochemical Mass Spectrometry (EMS). A study of oxidation processes is presented along with studies of propane adsorption at 0.40 V and 0.25 V, and at open circuit. The steady state current-potential curve for propane is discussed. The non-steady state oxidation of propane was studied at 0.40 V. Adsorption-desorption phenomena have been used to investigate the anodic behavior of propane at 0.40 V. The study was conducted principally to determine the effect of steady state oxidation on the adsorbate. The authors studied open-circuit adsorption of propane on platinum. The time dependencies of electrode phenomena at 0.25 V and at open circuit are presented and discussed. Using impurity corrected adsorption and charge data, the oxidation states of total, cathodically desorbable, and non-cathodically desorbable adsorbates formed at 0.25 V were determined. The results are summarized., See also report dated Dec 72, AD-762 356.

The properties of propane and propane-2-C13 adsorbates formed at 0.25 V vs. the polarized hydrogen electrode (0.274 vs. RHE) were examined using electrochemical mass spectrometry (EMS). Experimental results indicate the presence of adsorbable organic impurities which compete with propane for adsorption sites. Based on the time dependence of inhibition of hydrogen adsorption, the impurity level appears comparable to that of earlier workers. All of the C(13)C2H8 adsorbed can be accounted for on the basis of products desorbed at either 0.05 V (propane and ethane) or at large anodic potentials (carbon dioxide). The results support the view that (1) propane formed on cathodic desorption arises from the original carbon skeleton of the absorbable propane and (2) methane produced at 0.25 V is produced with equal probability from all carbons in the original propane. (Modified author abstract), See also report dated Jun 72, AD-755 254.

Propane oxidation was studied using electrochemical mass spectrometry as part of a research study for the development of a propane air fuel cell. An investigation of the cathodic desorption product distribution as a function of the potential of propane adsorption was carried out. The product distribution was found to be highly dependent on adsorption potential. Using coulometric and desorption data, the degree of oxidation per adsorbed carbon for both cathodically desorbable and non-cathodically desorbable species has been calculated. From these data, it has been possible to speculate on the nature of adsorbed intermediates in the propane oxidation reaction. Advances in porous electrode theory and construction are also discussed. (Author), Errata sheet inserted. See also AD-743 190.

Electrochemical Mass Spectrometry was used to determine the absolute amounts of desorbable C-1, C-2 and C-3 species from propane adsorbed on a platinum electrode at 0.3V. The construction of porous electrodes as well as a brief presentation of their theory and application is given. A method for synthesizing propane-2-(13)C from acetic acid-1-(13)C is presented. (Author)

A reproducible procedure of seeded growth in stable supersaturated solutions was successfully applied to the growth and dissolution of dicalcium phosphate (DCP) and to the growth of synthetic hydroxyapatite (HAP) crystals. The influence of a number of added substances, known to be effective inhibitors of caries production, upon these processes was investigated both chemically and microscopically. (Author)

Iminium cations can be generated by ionization of oxime polyphosphates of rigid ketones incapable of rearrangement and fragmentation. This report summarizes a research effort to determine whether singlet or triplet ions are involved as intermediates in appropriate compounds when they react to produce C-H insertion and non-stereospecific rearrangement products. Another goal of this research was to find substrates where remote intramolecular nucleophilic attack at nitrogen would supersede the conventional Beckmann isomerization. (Author)

A brief review of the author's research is presented. Part of the investigation studied the chemical response to ultraviolet radiation of several small ring heterocyclic systems. The phototransformations of beta, gamma-epoxy ketones, dibenzoylstilbene episulfides, arylaroylazetidines, cyclopentyl phenyl ketone, and alpha-diazoacetophenone were examined in mechanistic detail. Photosensitization, quenching, and emission studies were performed in order to describe the excited states involved in these photoreactions as well as to provide for a better understanding of the mechanism of these transformations. (Author)