The Henderson Approximation and the Mass Action Law of Guldberg and Waage

Using contemporary accounts, we describe the scope of the Henderson approximation, and its relationship to the mass action law of Guldberg & Waage. The Henderson approximation, apparently written in logarithmic form by Hasselbalch, has the same form as the mass action law, but has a completely different meaning and a much more restricted range of applicability. The Guldberg-Waage law is the fundamental mass action relationship valid for all chemical equilibria, whereas the Henderson approximation is useful only within a limited range of a sufficiently concentrated two-component buffer mixture.     

Membrane admittance measurements under computer control

The application of the elegant Fourier transform method of Smith et al.^3,4 to measurements on ultrathin, “black” lipid membrane is described. A digital computer generates a waveform containing many frequencies, applies it to the measurement cell containing an artificial, ultrathin membrane, collects the resulting electrical response, extracts the cell admittance by a substitution method, and facilitates subsequent numerical data analysis. The performance of the instrument is illustrated.     

Simple charging current correction in dc polarography

This paper demonstrates the strong interaction between molecular iodine and surface atoms of III - V compounds such as InP and GaP.The mechanism of the iodine reduction is determined.     

Condensed thymine films at the mercury/water interface: Part V. Phase transitions

The topography of the various phase transitions in a supersaturated thymine solution is described. Most transitions leading from a non-condensed to a condensed film involve nucleation and growth, via a metastable intermediate surface state, as do some transitions between condensed films. The latter have unusually high Avrami slopes and, sometimes, involve multiple intermediate states. Other transitions exhibit exponential transients. Of the three pit regions observed, that at the most positive potentials is present only in super-saturated solutions, is clearly associated with three-dimensional phase formation, and does not lead to a well-defined steady-state interfacial capacitance. Most transitions leading to a non-condensed final state exhibit exponential transients.     

Double-layer dynamics in the adsorption of tetrabutylammonium ions at the mercury | water interface Part 4. The reduction of hexammine-cobalt(III) through tetrabutylammonium films

The reduction of hexamminecobalt(III) at the mercury-water interface is strongly affected by the presence of a condensed tetrabutylammonium film. When the anions present are fluoride and/or tetrafluoroborate, electron transfer through the film proceeds via an inner-sphere mechanism, i.e. the film must be opened so that hexamminecobalt(III) can make direct contact with the metal. In the presence of bromide anions, an outer-sphere pathway is indicated, probably involving bridging by bromide ions. Unusual current-time transients of the reduction of hexamminecobalt(III) in the presence of tetrabutylammonium ions are correlated with the kinetics of film formation.     

Electrochemistry of artificial ultrathin lipid membranes: A review

The electrochemical reduction of oxygen in acid solution was studied at rotated electrodes of eight different pyrite specimens which were electrically characterized and included n-type, n-type metallic and p-type examples. Shapes of voltammograms, Tafel slopes and electrocatalytic activities for oxygen reduction all showed a degree of variation from sample to sample, but no correlation of behaviour with semiconducting type could be established.     

Existence of uncertainty minimizers for the continuous wavelet transform

Continuous wavelet design is the endeavor to construct mother wavelets with desirable properties for the continuous wavelet transform (CWT). One class of methods for choosing a mother wavelet involves minimizing a functional, called the wavelet uncertainty functional. Recently, two new wavelet uncertainty functionals were derived from theoretical foundations. In both approaches, the uncertainty of a mother wavelet describes its concentration, or accuracy, as a time-scale probe. While an uncertainty minimizing mother wavelet can be proven to have desirable localization properties, the existence of such a minimizer was never studied. In this paper, we prove the existence of minimizers for the two uncertainty functionals.     

On the admittance of lipid bilayer membranes: Part II. Uncouplers and ion carriers

Rangarajan's modular formalism has been applied to those cases in which ion transport across an ultra-thin membrane is associated with membrane permeation of a neutral species. A single connectivity diagram can be used to represent the admittance in the presence of an ion carrier or of either a monomeric or a dimeric uncoupler.     

Generation and trapping of 2,3-naphthoquinone

2,3-Naphthoquinone generated from 2,3-dihydroxynaphthalene was trapped with cyclopentadiene and its properties examined by dc polarography and cyclic voltametry.