Water, formation composition variations

Various mechanisms for electret effect formation in anodic oxides have been proposed. Lobushkin and co-workers241,242 assumed that it is caused by electrons captured at deep trap levels in oxides. This point of view was supported by Zudov and Zudova.244,250 Mikho and Koleboshin272 postulated that the surface charge of anodic oxides is caused by dissociation of water molecules at the oxide-electrolyte interface and absorption of OH groups. This mechanism was put forward to explain the restoration of the electret effect by UV irradiation of depolarized samples. Parkhutik and Shershulskii62 assumed that the electret effect is caused by the accumulation of incorporated anions into the growing oxide. They based their conclusions on measurements of the kinetics of Us accumulation in anodic oxides and comparative analyses of the kinetics of chemical composition variation of growing oxides. 

PCBs and the Environment. Waid JS (ed) CRC Press, Boca Raton, p 1-45 Coleman ML (1992) Water composition variation within one formation. In Water-Rock Interaction Proceeding of 7" international symposium on water-rock interaction. Kharaka, Macst (eds) Park City, UT, p 1109-1112... 

Powders from All-Salt Compositions. An all-salt procedure has been described by Schafer et al. (1997) for the synthesis of lead zirconate titanate powders. The first step in the process was the mixing of aqueous solutions ofzirconyl and titanyl nitrates in stoichiometric proportions. Lead nitrate and citric acid were dissolved in this mixed solution. Nitric acid was also added to keep the solution clear after a water-evaporation step at 90°C. When the concentration of citric acid was higher than 22.1 mmol, there was no precipitation and the dehydrated solutions formed gels. Suitable thermal treatments (180°C, followed by 550°C/2 h) led to the formation of lead zirconate titanate solid solutions according to compositional variations. The primary particles had a size of about 50 nm. 

Prussian Blue. Reaction of [Fe(CN)3] with an excess of aqueous h on(Ill) produces the finely divided, intensely blue precipitate Pmssian Blue [1403843-8] (tetrairon(Ill) tris(hexakiscyanoferrate)), Fe4[Fe(CN)3]. Pmssian Blue is identical to Turnbull s Blue, the name which originally was given to the material produced by reaction of [Fe(CN)3] with excess aqueous h on(Il). The soHd contains or has absorbed on its surface a large and variable number of water molecules, potassium ions (if present in the reaction), and h on(Ill) oxide. The h on(Il) centers are low spin and diamagnetic h on(Ill) centers are high spin. Variations of composition and properties result from variations in reaction conditions. Rapid precipitation in the presence of potassium ion affords a colloidal suspension of Pmssian Blue [25869-98-1] which has the approximate composition KFe[Fe(CN)3]. Pmssian Blue compounds are used as pigments in inks and paints and its formation on sensitized paper is utilized in the production of blueprints. 

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