III and Chromium

The reaction between arsenic(III) and chromium(VI) in 0.01-0.05 M sulphuric acid was studied by DeLury . On recomputing his data" taking into consideration the dichromate-hydrogen chromate equilibrium... 

Species may differ by oxidation state for example, manganese(II) and (IV) iron(II) and (III) and chromium(III) and (VI). Oxidation state is influenced by the redox potential. Mobility is affected because oxidation state influences precipitation-dissolution reactions and also toxicity in the case of heavy metals. 

X-ray powder diagrams obtained by the Guinier method show the tris (O-ethyl dithiocarbonato) complexes of chro-mium(III), indium(III), cobalt(III), iron(III), arsenic(III), and antimony(III) to be isomorphous. Carrai and Gottardi have determined the structure of the arsenic(III)18 and anti-mony(III)19 complexes. Crystallographic data for the cobalt(III) and chromium(III) ethylxanthate complexes are given by Derenzini20 and Franzini and Schiaffino,21 respectively. 

Collection of Chromium (III) and Chromium (VI) with Hydrated Iron (III) or Bismuth Oxide... 

Only chromium (III) co-precipitates quantitatively with hydrated iron (III) oxide at the pH of seawater, around 8. In order to collect chromium (VI) directly without pre-treatment, e.g., reduction to chromium (III), hydrated bismuth oxide, which forms an insoluble compound with chromium (VI) was used. Chromium (III) is collected with hydrated bismuth oxide (50 mg per 400 ml seawater). Chromium (VI) in seawater is collected at about pH 4 and chromium (VI) is collected below pH 10. Thus both chromium (III) and chromium (VI) are collected quantitatively at the pH of seawater, i.e., around 8. 

Mullins [37] has described a procedure for determining the concentrations of dissolved chromium species in seawater. Chromium (III) and chromium (VI) separated by co-precipitation with hydrated iron (III) oxide and total chromium are determined separately by conversion to chromium (VI), extraction with ammonium pyrrolidine diethyl dithiocarbamate into methyl isobutyl ketone, and determination by AAS. The detection limit is 40 ng/1 chromium. The dissolved chromium not amenable to separation and direct extraction is calculated by difference. In waters investigated, total concentrations were relatively high (1-5 xg/l), with chromium (VI) the predominant species in all areas sampled with one exception, where organically bound chromium was the major species. 

Parts per billion concentrations of chromium (III) and chromium (VI) in seawater have been determined using high-performance liquid chromatography in conjunction with inductively coupled plasma mass spectrometry [196]. 

Octamethyldimetalates of Molybdenum(II), Rhenium(III), and Chromium(II) - Assignment of Delta-Delta Transition. 

Altman C, King EL (1961) The mechanism of the exchange of chromium(III) and chromium(VI) in acidic solution. J Amer Chem Soc 83 2825-2830... 

Term labels appropriate for d3 and d6 configurations in octahedral ligand fields will be used in this review to designate the ligand field or d-d excited states of cobalt(III) and chromium(III) complexes. This... 

It will become evident from this discussion of cobalt(III) and chromium(III) photochemistry that a fortunate combination of many factors makes these systems especially amenable to mechanistic investigation this is not the case for most other inorganic systems. For this reason, the progress made toward understanding the photochemical reactions of cobalt(III) and chromium(III) complexes may not be easily duplicated in other areas and it is useful to inquire whether conclusions reached here can be generalized. It is my belief that they can, and this and the next section are intended to place the subsequent discussion in the perspective of inorganic photochemistry. 

Two rather different points of view have been maintained concerning the general question of mechanisms in inorganic photochemistry. This section defines both of these and attempts to indicate the evidence in favor of each subsequent sections will consider in detail the applicability of various mechanistic proposals to the study of the photochemistry of cobalt(III) and chromium(III). 

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