Utilisation des courbes de polarisation dans les dosages électrochimiques: Coulométrie á intensité constante

The conditions for coulometric determinations at constant intensity can be deduced from the polarisation curves; these are choice of current density and auxiliary systems, and possible accuracy of the determination. We have used for this study the results previously obtained for potentiometry at constant intensity.     

Remarques sur les définitions des acides et des bases

In the present state of knowledge it is not possible to account for the reactions used in analytical chemistry by setting up a single table of the “acids” and “bases” defined according to LEWIS.The most general definition which can be usefully adopted involves taking into account the exchange of “particles” (electrons, protons, ions, molecules) in the reactions. It follows from this that there arc as many types of reactions as there are “particles”.In accordance with the brönsted theory, in the case where the “particle” exchanged is the proton, an acid-base reaction is involved.     

Une généralisation de la théorie de brönsted en chimie analytique

The proposal is made that all reactions be considered as corresponding to the exchange of particles (particules).1. Exchange of electrons between an oxidising agent and a reducing agent. This is the classical conception of oxidation-reduction reactions.2. Exchange of ions (or of polar molecules) between an “acceptor” of the ion and a “donor” of the same ion. In the case of exchange of protons the reaction is one between acids and bases, according to Brönsted.The majority of reactions concern the exchange of different ions. It is proposed to apply to these reactions, and that for each type of particle exchanged, the type of reasoning which Brönsted has used for the exchange of protons.The analogy thus created between the different types of reactions leads to a considerable simplification. It allows identical reasoning and the use of similar formulations for all reactions.Further, the distinction between reactions in terms of the nature of the particle exchanged permits recognition of the respective influence of the factors which are available for controlling the reactions.It is suggested that the use of this conception is advantageous in teaching analytical chemistry.     

Polydentate phosphines

Phosphines are one of the most important classes of ligands in chemistry, in both the industrial and academic spheres. This review deals with the design and properties of polydentate phosphines, an original and broad class of multidentate ligands. The multidentate nature of these species has led to special properties, in which the spatial proximity of phosphorus atoms is crucial. The first part gives an overview of oligodentates polyphosphines in which is discussed the types and the basic routes for their synthesis. The review continues with the most important synthetic routes for obtaining complexes. Because of huge amount of literature data this review is not exhaustive, but it collects the most relevant findings in this area. The restriction to structural and spectroscopic properties allows us for a well organized handling of the complex material.     

A versatile synthesis of a new bisiminophosphorane

The iminophosphorane CH₂CH₂[P{NP(O)(OPh)₂}Ph₂]₂ is synthesized in high yields (80–97%) via a very convenient procedure using diphenylphosphoryl azide (DPPA) and 1,2-bis(diphenylphosphino)ethane.     

Electron reconstruction in CMS

The reconstruction of the energy and momentum of isolated electrons in CMS combining tracking and electromagnetic calorimetry information is described. The emphasis is put on primary electrons with transverse momentum below 50 GeV/c. The energy deposited in the electromagnetic calorimeter is measured in clusters of clusters (superclusters) which collect bremsstrahlung photons emitted along the electron trajectory in the tracker volume. The electron tracks are built from seeds in the pixel detector found via a cluster-driven pixel hit matching algorithm, followed by a reconstruction of trajectories in the silicon strip tracker with a Gaussian sum filter. Electrons are classified using observables sensitive to the pattern of bremsstrahlung emission and electromagnetic showering in the tracker material. Energy scale corrections depending on the electron class are applied to the supercluster and estimates of associated errors are obtained. The electron energy is deduced from a weighted combination of the corrected supercluster energy and tracker momentum measurements. The electron direction is that of the reconstructed electron track at interaction vertex. The pre-selection of isolated electron candidates for physics analysis is described. Class-dependent observables combining tracking and calorimetry information are discussed for electron identification.     

Chemical Profile,Antioxidant Capacity,and Antimicrobial Activity of Essential Oils Extracted from Three Different Varieties (Moldoveanca 4, Vis Magic 10, and Alba 7) of Lavandula angustifolia

Chemical composition, antioxidant capacity, and antimicrobial activity of lavender essential oils (LEOs) extracted from three different varieties of Lavandula angustifolia Mill. (1-Moldoveanca 4, 2-Vis magic 10, and 3-Alba 7) have been determined. These plants previously patented in the Republic of Moldova were cultivated in an organic agriculture system in the northeastern part of Romania and then harvested in 3 consecutive years (2017–2019) to obtain the essential oils. From the inflorescences in the complete flowering stage, the LEOs were extracted by hydrodistillation. Then, their composition was analyzed by gas chromatography coupled with mass spectrometry (GC-MS) and by Fourier Transformed Infrared spectroscopy (FT-IR). The major identified constituents are as follows: linalool (1: 32.19–46.83%; 2: 29.93–30.97%; 3: 31.97–33.77%), linalyl acetate (1: 17.70–35.18%; 2: 27.55–37.13%; 3: 28.03–35.32%), and terpinen-4-ol (1: 3.63–7.70%; 2: 3.06–7.16%; 3: 3.10–6.53%). The antioxidant capacity as determined by ABTS and DPPH assays indicates inhibition, with the highest activity obtained for LEO var. Alba 7 from 2019. The in vitro antimicrobial activities of the LEOs and combinations were investigated as well, by using the disk diffusion method and minimum inhibitory concentration (MIC) against the Gram-positive bacterial strain Staphylococcus aureus (ATCC 6538), Gram-negative Pseudomonas aeruginosa (ATCC 27858), Escherichia coli (ATCC 25922), the yeast Candida albicans (ATCC 10231), and clinical isolates. Our results have shown that LEOs obtained from the three studied varieties of L. angustifolia manifest significant bactericidal effects against tested microorganisms (Staphylococcus aureus and Escherichia coli), and antifungal effects against Candida albicans. The mixture of LEOs (Var. Alba 7) and geranium, respectively, in tea tree EOs, in different ratios, showed a significant enhancement of the antibacterial effect against all the studied strains, except Pseudomonas aeruginosa.