Uranyl chromate

Fig. 35. Stnictures of four uranyl chromate hydrates with the general composition [U02(Cr04)(H20)2](H20)n projected along the chain extension [n = 0 (a), 1 (c), 2.25 (b), and 3.5...

N. A. Orloff, when potassium chronoate is added to an aq. soln. of uranyl chromate, the basic salt, yellow uranyl oxybischromate, UO3.2UO2CrO4.8H2O, or... 

J. Formanek obtained silver uranyl chromate as a vermilion precipitate by treating a soln. of uranyl chromate with silver nitrate. Unlike J. Formanek, B. Szilard was unable to detect any decomposition of silver uranyl chromate in light even after several days exposure. J. Formanek prepared mercurous uranyl chromate in a similar manner so also lead uranyl chromate and hismuth uranyl chromate. 

Uranyl chromate. Uranyl chromate solutions also suffer from hydrolysis at elevated temperatures excess chromic acid is required for stability [18]. This system is, however, not unattractive insofar as corrosion of stainless and carbon steels is concerned. The conditions of acidity and oxidation-... 

Uranyl solutions are easily prepared by dissolution of water-soluble salts the nitrate, fluoride, chloride, bromide, iodide, sulfate, and acetate. Other water-soluble uranyl salts Include those of other organic acids the formate, propionate, butyrate, emd valerate and certain double salts such as potassliun uranyl sulfate, sodium uranyl carbonate, sodium uranyl chromate, etc. Uranyl solutions may be prepared also by dissolution of a uranium(VI) compound in an appropriate solvent, by dissolution of a lower valence uranium compound in an oxidizing medium, or by oxidation of lower valence uranium ions already in solution. Uranyl solutions are yellow in color. They are the most stable of uranlvim solutions. As indicated in preceding paragraphs, the... 

Several proteins were reported to function as enzymes for the dissimilatory reduction of metals and nonessential elements. As Usted in Table 16.4, the most frequently reported proteins involved in metal reduction are the cytochromes from sulfate-reducing bacteria. The focus on these cytochromes supports the initial papers by Lovley and colleagues in which they reported that reduced cytochrome Cs from Desulfovibrio vulgaris Hildenborough reduces uranyl salts (Lovley et al. 1993a) and chromate (Lovley and PhUhps 1994). 

At the highly charged extreme, the free metal cation is no longer a detectable species. Instead, ions such as permanganate (MnOq""), chromate (Cr04 ), uranyl (UO2 ), dioxovanadium (VOi "), and vanadyl (VO ) are formed, with oxidation... 

Oxoanions promote the formation of dimeric or polymeric products. The local coordination environment in these species is that of pentagonal bipyramidal uranyl groups with two neutral ligands and three 0x0 groups from two different bridging sulfate, chromate, or acetate groups. " ... 

Carey Lea failed to find any sensitising action of dyes on ferric oxalate, potassium chromate, uranyl nitrate, etc. The research of J. M. Eder was fundamental in the study of sensitisation by dyestuffs. J. J. Acworth found a rough correlation between the absorption maximum of a coloured silver bromide gelatin plate and the maximum of chemical activity in the region of the spectrum, although this was always displaced towards the violet. The development of this work into panchromatic plates is well known. 

Anions can also be transported by liquid membranes, e.g. nitrate (N03 ). chromate (Cr207- ) and uranyl (002(504)2 ). 

Operative Pathways of Chromate and Uranyl Reduction within Soils and Sediments... 

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