Oxyhydration

Reduction to S(IV) is the basis of two spot tests of Feigl, although these apply to other S(VI) classes, e.g. sulphonamides. Thus Feigl and Lenzer fused the sample with alkali to yield sulphite, then treating with hydrochloric acid and warming to expel sulphur dioxide they detected the latter with nickel(II) hydroxide on test paper, which yielded ultimately the black Ni(IV) oxyhydrate (see also Section C). In the other test FeigF fused the sample with sodium formate/alkali, cooled and acidified with sulphuric acid to liberate sulphur dioxide in this case also. This was detected by a ferric chloride/potassium ferricyanide reagent which yielded a blue colour (Prussian, Turnbull s). 

Rates of sorption and desorption of phosphate. Eur. J. Soil Sd. 48 101-114 Strens, R.G.S. Wood, B.J. (1979) Diffuse reflectance spectra and optical properties of some iron and titanium oxides and oxyhydr-oxides. Min. Mag. 43 347—354 Stumm, W. Eurrer, G. (1987) The dissolution of oxides and aluminum silicates Examples of surface-coordination-controlled kinetics. 

The form of nickel in particles from different industries varies. The mineralogical composition, chemical content, and form of dusts from nine industries in Cracow, Poland, were examined (Rybicka 1989). The chemical form of a particle-associated heavy metal that was assessed by a five-step extraction scheme classified the metal as exchangeable, easily reducible (manganese oxides, partly amorphous iron oxyhydrates and carbonates), moderately reducible (amorphous and poorly crystallized iron oxyhydrates), organically bound or sulfidic, and residual. Dusts from power plants had a silicate characteristic with quartz and mullite predominant. Approximately 90% of the nickel from these... 

Adsorbed As3+ Fe,Mn-(oxyhydr)oxides As Easily removed at high pH... 

Adsorbed Se6+ Fe,Mn-(oxyhydr)oxides Se Easily removed at all pH values... 

Fig. 11. Temperature dependence of current voltage curves of the anodic oxygen evolution from 30 wt% KOH at nickel anodes coated by mixtures of cobalt and iron oxyhydrates.

The redox mechanism applies not only to allylic oxidation of olefins and to the oxidation of aromatic hydrocarbons, but also to the oxidation of methanol and sulphur dioxide, as well as the oxidation of ammonia to nitrogen. Only in the case of ethylene oxidation and oxyhydration of olefins do catalysts act according to another mechanism. The latter processes seem to be always low temperature reactions, occurring below 300° C, whereas redox mechanisms are possible above this temperature (e.g. 400—500°C). 

The oxyhydration of propene to acetone occurs at a much lower temperature than the allylic oxidation and demands, in principle, the presence of excess steam. The reaction is initiated by addition of a proton from the catalyst surface and the acetone formation involves oxygen originating from water. 

The interest in palladium-based catalysts is due to the double bond oxyhydration capacity of palladium, unique among the noble metals, and well known from the Wacker process. Fuyimoto and Kunugi [119] report that palladium salts on active charcoal are excellent catalysts for the oxidation of olefins, particularly ethylene but the higher olefins as well. A selectivity of 89% with respect to acetone beside 10% aldehyde production is obtained at a conversion level of 27%, using excess water and a very low temperature (105°C). Careful analysis of the charcoal does not indicate that metal oxide impurities are of importance. 

Finally, oxyhydration reactions can also occur, analogous to the conversion of propene to acetone. n-Butenes can yield methyl ethyl ketone. 

With Sn—Mo oxides, Tan et al. [343] oxidized 1-pentene at 158° and 185° C to give an oxyhydration. The main product was methyl propyl ketone with a selectivity of 65 and 53%, respectively, and related conversion levels of 8 and 22%. The olefin isomerized rapidly. 

Correlation of total surface inventories, obtained by selective extraction of the mixing-cell, to thg degree granite alteration and to temperature, indicates that Co and DSe show a positive correlation with both alteration and temperature. Cobalt-60 and Se inventories for the experiments conducted with fresh granite at 20°C and at 60°C (Reference No. 37 and 34, Table III) indicate about a factor of two increase at 60 C, as would be expected from the production of oxyhydroxides baggd on th alter-ation rate data. Other residual inventories for Co and Se (Table III) follow a pattern consistent with increased oxyhydr-oxide inventories due to both alteration and elevated temperature. 

These observations support the hypothesis that the similarity of the cesium elemental distribution to that of iron in natural granite weathering profiles is a result of coincidental clay mineral production rather than a direct association with oxyhydr-oxides (14).. .. 

Alcohol Content of Ethyl Oxyhydrate (Flavor Chemicals), 585 Alcoholic Ferric Chloride TS, 852 Alcoholic Potassium Hydroxide, 0.5 N, 854... 

Redox processes are important for elements which can exist in more than one oxidation state in natural waters, e.g. Fe and Fe, Mn, and Mn. These are termed redox-sensitive elements. The redox conditions in natural waters often affect the mobility of these elements since the inherent solubility of different oxidation states of an element may vary considerably. For example, Mn is soluble whereas Mn is highly insoluble. In oxic systems, Mn is precipitated in the form of oxyhydr-oxides. In anoxic systems, Mn predominates and is able to diffuse along concentration gradients both upwards and downwards in a water column. This behaviour gives rise to the classic concentration profiles observed for Mn (and Fe) at oxic-anoxic interfaces as illustrated in Figure 2. 

The formation of oxyhydrate precipitates during the hydrolysis of silicon salts proceeds via the scheme ... 

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