Diffusion Of Hydroxyl Ions Research Articles

The creep of quartz single crystals, with special reference to the mechanism by which water accommodates dislocation glide

Abstract A geometrical description is presented which demonstrates that the core structure of static dislocations in α- and β-quartz can be electrostatically neutral. However, to preserve neutrality during dislocation multiplication and glide, it is postulated that water has to be extracted from nearby sources. This is relatively easy if the water is distributed as water molecules in interstitial solution but not if it is present in the form of droplets of second phase, because extraction of water from bubbles requires simultaneous bulk diffusion of silicon and oxygen. As a consequence, the activation energy for secondary creep is increased from 18 kcal mole−1, the value for diffusion of hydroxyl ions, to 31 kcal mole−1, the value for self-diffusion of oxygen in quartz. The direct observation of phase separation of water suggests a new interpretation for the well-known effect of superposed hydrostatic pressure on the plasticity of quartz, namely that it suppresses such phase separation and thereby maintains the supply of water to dislocations.

Oxygen incorporation in the alkaline earth fluorides

Le genre Cibaster, dont le type est Cibaster bourgeoisanus (d'Orbigny, 1853) de la « Craie de Villedieu », a été créé par Pomel en 1883, sur des caractères peu diagnostiques. Il a cependant été utilisé par de nombreux auteurs, tantôt comme un genre proche de Cardiaster Forbes, 1850, tantôt comme un genre voisin d'Offaster Desor, 1858. L'étude d'un grand nombre de spécimens provenant du Coniacien de la « Craie de Villedieu », dans la région stratotypique, permet de rapprocher le genre Cibaster du genre Cardiaster, dont il diffère à l'âge adulte par la persistance de pores juvéniles et d'un sillon frontal peu profond. Ainsi, le genre Cibaster est paedomorphique par rapport au genre Cardiaster. L'existence d'un plastron dérivé de celui du genre Pseudholaster Pomel, 1883, plaide pour une filiation Pseudholaster-Cibaster, probablement par l'intermédiaire du genre Protocardiaster Smith et Wright, 2003. En revanche, le genre Cibaster n'a aucun lien de parenté direct avec le genre Offaster, dont le plastron est typiquement méridosterne.The genus Cibaster Pomel, 1883, with its type species Cibaster bourgeoisanus (d'Orbigny, 1853), has poorly diagnostic characters. So, authors comprise this genus as Cardiaster Forbes, 1850, or as Offaster Desor, 1858. The study of numerous specimens of Cibaster bourgeoisanus, from the Coniacian of the “Craie de Villedieu” in the stratotypical region, demonstrates that this species is paedomorphic compared to Cardiaster, with juvenile pore-pairs and a shallow frontal groove. The plastron structure is derived from the pattern found in Pseudholaster Pomel, 1883. A close relationship between Pseudholaster and Cibaster is probable, with Protocardiaster Smith and Wright, 2003 as intermediate. Cibaster is clearly distinct from Offaster, because this last genus have a meridosternal plastron.

Oxygen incorporation in the alkaline earth fluorides

We consider the thermodynamics and kinetics of oxygen incorporation in the alkaline earth fluor ides, basing our discussion on the results of calculated energies of formation of a range of defects and defect clusters. Our results strongly suggest that oxygen may be incorporated only by hydrolysis and not by oxidation, and that the reaction will only occur in doped crystals. We propose a mechanism for the reaction, involving proton exchange at the surface of the crystals followed by diffusion of hydroxyl ions into the crystal; there they react with dopant-interstitial complexes to produce dopant-oxide complexes of types that have been detected in spin resonance studies.

Reply to Doremus

DOREMUS implies that the hydroxyl ion diffusion which I observed1 was in fact the result of the movement of monovalent cations, present as impurity ions in quartz. If this was so I was monitoring self-diffusion currents because I employed a platinum anode which was neither a source of alkali nor of hydrogen ions. The conductivity for a self-diffusion current decreases exponentially with time2 whereas for an ionic current the conductivity3,4 increases to a maximum constant value and therefore the one can be readily distinguished from the other. The currents I observed were of the latter type and the diffusing ions must have originated in the cathode. I used three different minerals, goethite, talc and kaolinite as cathodic sources of hydroxyl ions and observed a similar OH absorption band in the near infrared spectra of the quartz; I obtained a similar activation energy with each source. I did not detect an OH absorption band after self-diffusion experiments although this has been observed by others using a more sensitive infrared technique5.

Hydroxyl Ion Diffusion in Quartz

THE diffusion of univalent cations through quartz was first observed in 1887 (ref. 1) and has been the subject of several investigations since2,3. But there seems to be a lack of data on the movement of anions through the quartz lattice, although these ions are present in that mineral4. The most abundant anion, which may be present in greater quantities than the total cation content, is the hydroxyl ion5 which has been shown to weaken quartz by forming silanol bonds6. The formation of bubbles7, the accompanying decrease in silanol bonds and increase in free water8, in annealed quartz, indicate that the diffusion of hydroxyl ions must occur.

The Effect of High Pressure on the Voltage and Current Output of Silver Oxide‐Zinc and Mercury Oxide‐Zinc Miniature Batteries

The open circuit voltage (emf) and the voltage under load of alkaline silver oxide‐zinc and mercuric oxide‐zinc miniature batteries have been measured at pressures up to 20 kbars. The emf of these batteries varies with pressure in the manner expected based on the thermodynamics of the cell reactions. Pressure affects the voltage of the discharging silver oxide batteries only through its effect on the emf. The voltage of the discharging mercuric oxide battery is lowered with increasing pressure by approximately 5 mV/kbar. This decrease in voltage is due both to an increase in the over‐voltage at the electrode and also to the ohmic resistance. These pressure effects are discussed in terms of the postulated diffusion of hydroxyl ions through water channels in the reduced oxide and the influence of these channels on the number of oxide sites at which reduction may occur.

Simultaneous electrodeposition of nickel and hydrogen on a rotating disk electrode

Thin nickel layers have been deposited from 1 M NiSO4 solutions on a rotating disk electrode at various angular speeds up to 911 radian/sec. Deposits have been obtained only at current densities that exceed a certain minimum value. This minimum current density is equal to the diffusion-limited current density of the H3O+ ions below pH 3 as has been shown by its dependence on the angular speed of the electrode and on the pH of the solution. Above pH 3 this minimum current density, which is equal to the partial current density of the hydrogen evolution at higher total current densities, depends less on pH than expected; it is, therefore, limited by the diffusion of hydroxyl or complex ions.

Simultaneous electrodeposition of nickel and hydrogen on a rotating disk electrode

Thin nickel layers have been deposited from 1 M NiSO4 solutions on a rotating disk electrode at various angular speeds up to 911 radian/sec. Deposits have been obtained only at current densities that exceed a certain minimum value. This minimum current density is equal to the diffusion-limited current density of the H3O+ ions below pH 3 as has been shown by its dependence on the angular speed of the electrode and on the pH of the solution. Above pH 3 this minimum current density, which is equal to the partial current density of the hydrogen evolution at higher total current densities, depends less on pH than expected; it is, therefore, limited by the diffusion of hydroxyl or complex ions.

PROTONIC CONDUCTION OF ARTIFICIAL LIPID MEMBRANES

Electrical conductance of phospholipid bilayer membranes formed in various electrolyte solutions was studied with special reference to the kind of related charge carriers. The conductance was extremely low (10-5-10-7mho-cm-2), depending considerably on the lipid composition but little on both the concentration and kind of the electrolytes used, and it showed a complex dependence on the pH of the media on both sides of the membrane. Because of these experimental results, it seems preferable to assume that the charge carriers through the membrane are not the ions supplied from the electrolyte added to the solution, but protons and hydroxyl ions whose mobilities depend upon the sign and magnitude of the net charge on the membrane. Potential differences caused by diffusion of protons or hydroxyl ions across the membrane were also determined to prove the above assumption.

Über die elektrochemische oxydation von jodid zum jodat an graphitelektroden

Disk electrodes consisting of Graphite-azobenzene'-mixtures were used. The total height of both waves, one due to hypoiodite formation and the other to iodate formation, is determined by the diffusion of hydroxyl ion to the electrode, if the solution is not buffered and if the hydroxyl ion concentration lies within a certain range. It was thus possible to determine the diffusion coefficient the hydroxyl ion as a function of ionic strength. An analysis of the potential/current- density diagrams of iodate formation shows that the electron-transfer reaction is first order with respect to iodide, 0·23 order with respect to OH − ion in the pH range 6–10·6 and zero order at higher pH values. This and other observations lead to the conclusion that iodide ions discharge on those portions where hydroxyl ions are adsorbed on the surface, the adsorption being governed by an adsorption isotherm of the Freundlich type. Some further qualitative observations support the mechanism OH aq− ⇌(OH) ad− I − + (OH −) ad− →(JOH −) ad + e. The dependence of half-wave potential on rate of rotation and pH are in quantitative agreement with the mechanism proposed. The height of the diffusion-controlled limiting current of iodate formation in the presence varying amounts of phosphoric acid shows that increasing phosphoric acid content of the solution decreases the iodide diffusion coefficient.

The Rôle, of Hydrogen- and Hydroxyl-Ion Diffusion in Nerve and Muscle Action

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Rôle, of Hydrogen- and Hydroxyl-Ion Diffusion in Nerve and Muscle ActionE. Q. AdamsE. Q. AdamsMore by E. Q. AdamsCite this: J. Phys. Chem. 1922, 26, 7, 639–646Publication Date (Print):October 1, 1922Publication History Published online1 May 2002Published inissue 1 October 1922https://doi.org/10.1021/j150223a004RIGHTS & PERMISSIONSArticle Views26Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (412 KB) Get e-Alerts