Showing papers on "Chemical binding published in 1968"

Molecular Charge Distributions and Chemical Binding. III. The Isoelectronic Series N2, CO, BF, and C2, BeO, LiF

Abstract: The chemical binding and properties of the two isoelectronic series N2, CO, BF, a 14‐electron series, and C2, BeO, LiF, a 12‐electron series, are discussed in terms of the molecular charge distributions and the forces which they exert on the nuclei. It is found that the formation of the chemical bond in the 14‐electron series results in a transfer of charge from the bonding to the nonbonded regions of both nuclei in the molecule, the amount transferred increasing with the increasing asymmetry of the nuclear potential field. The larger and more diffuse nonbonded charge increase on B in BF as compared to that on C in CO suggests that BF may be superior to CO in its ability to act as a ligand in metal complexes. The increasing asymmetry of the potential field in the 12‐electron series results in a parallel increase in the asymmetry of the molecular charge distributions. Unlike the 14‐electron series, the charge transfer in BeO and LiF is unidirectional. The Δρ(e, η) or density difference contour maps [ρ(mole...

Chemical binding of protective agents to the human stratum corneum.

Abstract: : Report covers laboratory study and clinical trials on a series of chemical formulations to find means of chemically binding agents to skin elements or of permanent absorption to provide long term (7 days) protection from sunburn regardless of heavy sweating or washing actions. Results are reported in detail and tabulated. Two preparations were developed which were effective for long term exposure (4 hr) after single application and were resistant to washing action. Preparations did not interfere with tanning action and were cosmetically acceptable. Two were very effective under conditions of bright sun in dry climate or high elevation and snow environments. Stable binding to skin providing 7-day or longer protection was not achieved. (Author)

Thermodynamics and Defect Chemistry of Some Oxide Solid Solutions Part II: Pair Interactions

Abstract: This paper is concerned with solid solutions of two isostructural ionic oxides. Relations are derived between activities and composition on the assumptions that interactions between nearest and next-nearest neighbours are involved, and that the distribution of the cations present in any sublattice is random. Proof is given that such solutions will be regular if they show no substitutional disorder. A comparison is made with some experimental data given in the literature. The available data show that binary systems of halides, silicates, oxides with rock-salt structure and oxides with spinel structure are indeed regular, if there is no substitutional disorder. The energy of interactions between next-nearest neighbours could be evaluated and varied from – 3 to +4 kcal/mol. The nature of these interactions is discussed. It is shown that the „interaction” energy originates from Coulomb energy, crystal-field stabilization and deviations from stoichiometry with respect to the oxygen content and that further the chemical binding between next-nearest neighbours is negligibly small except in solid solutions of Fe3O4 and inverse ferrites with other spinels. Die vorliegende Arbeit befast sich mit festen Losungen zweier isostruktureller ionischer Oxide. Unter der Voraussetzung, das Wechselwirkungen zwischen nachsten und ubernachsten Nachbarn eine Rolle spielen und das die Verteilung der Kationen in jedem Untergitter zufallig ist, werden Beziehungen zwischen den Aktivitaten und der Zusammensetzung abgeleitet. Es wird bewiesen, das solche Losungen regular sind, wenn sie keine Substitutionsfehlordnung aufweisen. Die Ergebnisse werden mit einigen in der Literatur angegebenen experimentellen Befunden verglichen. Die vorhandenen Meswerte zeigen, das binare Systeme von Halogeniden, Silikaten, Oxiden mit Steinsalzstruktur und Oxiden mit Spinellstruktur tatsachlich regular sind, wenn keine Substitutionsfehlordnung vorhanden ist. Die Wechselwirkungsenergie zwischen ubernachsten Nachbarn konnte ermittelt werden; sie variierte zwischen - 3 und +4 kcal/mol. Die Natur dieser Wechselwirkungen wird diskutiert. Es wird gezeigt, das die „Wechselwirkungsenergie” aus Coulomb-Energie, Kristallfeldstabilisierung und Abweichungen des Sauerstoffgehalts von der Stochiometrie herruhrt und das auserdem die chemische Bindung zwischen ubernachsten Nachbarn vernachlassigbar klein ist, auser bei festen Losungen von Fe3O4 und inversen Ferriten mit anderen Spinellen.