Publisher Summary This review is concerned with the neglected class of inorganic compounds, which contain ions of the same element in two different formal states of oxidation. Although the number of references cited in our review show that many individual examples of this class have been studied, yet they have very rarely been treated as a class, and there has never before, to our knowledge, been a systematic attempt to classify their properties in terms of their electronic and molecular structures. In the past, systems containing an element in two different states of oxidation have gone by various names, the terms “mixed valence,” nonintegral valence,” “mixed oxidation,” “oscillating valency,” and “controlled valency” being used interchangeably. Actually, none of these is completely accurate or all-embracing, but in our hope to avoid the introduction of yet another definition, we have somewhat arbitrarily adopted the phrase “mixed valence” for the description of these systems. The concept of resonance among various valence bond structures is one of the cornerstones of modern organic chemistry.

Mixed Valence Chemistry-A Survey and Classification

Aqueous pyrite oxidation by dissolved oxygen and by ferric iron

The authors studies of aqueous, abiotic pyrite oxidation in oxygen-saturated and anaerobic Fe(III)-saturated systems span pH values from 2 to 9 and include analyses of sulfite, thiosulfate, polythionates, and sulfate. In addition, they evaluated procedures for cleaning oxidation products from pyrite surfaces. As in silicate experiments, the preparation of the pyrite surface is critical to a valid interpretation of the onset of pyrite oxidation. The rates in oxygen-saturated systems (1) were relatively independent of pH, (2) gave linear sulfoxy anion production, (3) produced thiosulfate and polythionates at pH >3.9, and (4) produced intermediate sulfoxy anions only at high stirring rates. In anaerobic Fe(III)-saturated systems no intermediates were observed. From these results, along with the generally faster rate of oxidation in Fe(III)-saturated systems, we conclude that Fe(III) is the more important, direct oxidant of pyrite. This conclusion is supported by theoretical consideration regarding the low probability of a direct reaction between paramagnetic molecular oxygen and diamagnetic disulfide. The authors findings extend earlier models for the pyrite oxidation mechanism because of the larger range of experimental conditions that they have studied. Preliminary results from studies of sphalerite oxidation, in which they have found thiosulfate, support the hypothesis that thiosulfate is a keymore » intermediate related to the reaction mechanisms, independent of the bounding structure of the sulfide mineral.« less

Initiation of aqueous pyrite oxidation by dissolved oxygen and by ferric iron

Publisher Summary A number of recent crystal structure determinations on compounds of the nonmetals have discovered intramolecular distances that are much longer than normal bonds, and intermolecular distances that are much shorter than van der Waals distances. In this chapter, these interactions are examined and a qualitative explanation is attempted. It will become clear that in most of them an approximately linear arrangement is found, Y-A—X where Y-A is a normal bond and A—X is a short intermolecular distance. It is with these approximately linear interactions that we are particularly concerned, and it will be our contention that they are the result of directed forces and that their behavior is sufficiently regular and understandable for the name secondary bond to be appropriate. The only conclusive method of establishing the presence of secondary interactions is by crystal structure determinations. An intermolecular interaction can be recognized as being significant by being shorter than the expected intermolecular (van der Waals) distance, but if it is the result of directed forces— that is, bonds rather than electrostatic or nondirectional van der Waals forces.

Secondary Bonding to Nonmetallic Elements

Summary.

Cholic acid-24-14C has been given to male medical students. The specific activity of the circulating cholic acid has been followed. The half-life was 2.8 days and the size of the pool 3.58 g. From values of the quantitative composition of the bile the chenodeoxycholic and deoxycholic acid pools have been calculated.

The Turnover of Cholic Acid in Man.* Bile Acids and Steroids 51.

/pdf/the-prevalence-of-unbranched-sulphur-chains-in-polysulphides-3j9ocai6q8.pdf

The Prevalence of Unbranched Sulphur Chains in Polysulphides and Polythionic Compounds.

/pdf/the-crystal-and-molecular-structure-of-1-2-dithiolane-4-2qbk9s24hv.pdf

The Crystal and Molecular Structure of 1,2-Dithiolane-4-Carboxylic Acid.

/pdf/displacement-of-sulphite-groups-of-polythionates-by-41kyj7axi0.pdf

Displacement of Sulphite Groups of Polythionates by Thiosulphate.

/pdf/the-constitution-of-the-formamidinium-disulfide-ion-from-the-4b923gtwou.pdf

The Constitution of the Formamidinium Disulfide Ion, from the Crystal Structures of the Diiodide and Dibromide.

/pdf/salts-of-monotelluropentathionic-acid-2sb9h87obz.pdf

Olav Foss

Papers

The Prevalence of Unbranched Sulphur Chains in Polysulphides and Polythionic Compounds.

The Crystal and Molecular Structure of 1,2-Dithiolane-4-Carboxylic Acid.

Displacement of Sulphite Groups of Polythionates by Thiosulphate.

The Constitution of the Formamidinium Disulfide Ion, from the Crystal Structures of the Diiodide and Dibromide.

Salts of Monotelluropentathionic Acid.