Gaston Charlot

Bio: Gaston Charlot is an academic researcher. The author has contributed to research in topics: Electrochemical cell. The author has an hindex of 8, co-authored 16 publications receiving 1891 citations.

Méthodes modernes d'analyse quantitative minérale

Abstract: Sommaire : I - Generalite : I.Generalites sur la volumetrie II.Acidimetrie III.Oxydimetrie IV.Oxydants et reducteurs V.Titrimetrie par precipitation VI.Titrimetrie par formation d'ions complexes VII.Dosages electrometriques ou potentiometriques VIII.Electrolyse IX.Polarographie et titrages polarometriques X.Colorimetrie XI.Methodes physiques variees XII.Gravimetrie XIII.Analyse des gaz XIV.Reactifs organiques d'emploi general XV.Semimicro et micro-dosages XVI.Mise en solution XVII.Destruction des matieres organiques en vue du dosage des elements mineraux B/Dosage des principaux elements mineraux : I.Elements a chlorures insolubles II.Elements dont les sulfures sont insolubles en milieu acide III.Groupe de l'ammoniaque et groupe du sulfure d'ammonium IV.Alcalino-terreux V.Alcalins VI.Metalloides VII.Analyse des alliages VIII.Analyse des roches silicatees

Sites of metal deposition in the cell wall of Bacillus subtilis.

Abstract: Amine and carboxyl groups of the cell wall of Bacillus subtilis were chemically modified individually to neutralize their electrochemical charge for determination of their contribution to the metal uptake process. Mild alkali treatment removed ca. 94% of the constituent teichoic acid (expressed as inorganic phosphorus) and allowed estimation of metal interaction with phosphodiester bonds. Chemical modifications of amine functions did not reduce the metal uptake values as compared to native walls, whereas extraction of teichoic acid caused a stoichiometric reduction in levels. In contrast, alteration of carboxyl groups severely limited metal deposition of most of the metals tested. X-ray diffraction and electron microscopy suggested, in this case, that the form and structure of the metal deposit could be different from that found in native walls. The observations suggest that carboxyl groups provide the major site of metal deposition in the B. subtilis wall.

The surface chemistry of hydrous manganese dioxide

Abstract: An experimental investigation has shown that H+ and OH− are potential determining ions for the δMnO2 surface The pH (ZPC) was determined using electrophoretic mobilities and Na+ and K+ adsorption and found to be 225 Alkalimetric titration curves failed to provide a direct determination of the pH (ZPC), however, when combined with the Na+ adsorption data they provide a means for estimating the surface charge Surface charge values of approximately 100 μ C/cm2 were found at pH 8, considerably higher than the charge on SiO2 which has a similar pH (ZPC) Below pH 35 manganese was released to solution and the experimental data suggest that this is due to the reduction of MnO2 δMnO2 is thermodynamically unstable with respect to H2O below that pH

Light hydrocarbons in recent Texas continental shelf and slope sediments

Abstract: The distributions of the concentrations of methane, ethene, ethane, propene, and propane in twelve l-to 2-m-long gravity cores for two transects from nearshore to midslope off the southwest Texas Gulf Coast are reported. Methane profiles exhibit maxima in the top 40 cm of sediment on the shelf, in contrast to downward increasing gradients in the slope region. Nearshore surface methane concentrations ranging from 50 to 400 tl (normal temperature and pressure) per liter pore water are apparently due to microbial production ijsulfate-free microenvironments such as fecal pellets in a near-seawater sulfate environment. A decrease in sediment methane levels to less than 5 tl/l pore water in downslope sediments is attributed to reduced microbial activity due to lower organic contents and temperatures. Profiles of the saturated and unsaturated C: and Ca hydrocarbons suggest that these gases are also microbia!ly produced. plastic liner, was removed from the core barrel and sectioned at specific depths. Five-centimeter sections were immediately extruded into 0.5-1 containers holding 125 ml of sodium-azide- poisoned hydrocarbon-free seawater. The containers were capped, and the headspaces flushed with helium or nitrogen through septa in the lids. The hydrocarbon gases dissolved in the interstitial water were equilibrated with the gas phase by agitation for 5 min with a high-speed shaker. The shaker also dispersed the sodium azide throughout the sediment to inhibit microbial activity. The headspace gases were then analyzed, or the containers were inverted to form liquid seals around the lids and stored in darkness at near-freezing temperatures until analysis.

High valence 3p and transition metal based MOFs

Abstract: This article focuses on high valence 3p and transition metal based metal organic frameworks. In the first part we will discuss the complex solution chemistry of these metals which makes this sub-class of MOFs more of a challenge than the traditional low valence metal based MOFs. This is followed by a short review of the different classes of solids based on phosphonates, carboxylates and other linkers. Finally, we report some of the most relevant properties of these solids such as their chemical or thermal stability as well as their catalytic, redox- and photo-activities.