Oxidized gels

Plot of pMp° - p) against p/p° (r is expressed in cm (stp)). (1) Unpromoted Fe catalyst (2) AljOj-promoted Fe catalyst (3) AI2O3-KjO-promoted Fe catalyst (4) fused copper catalyst (5) chromium oxide gel (6) silica gel. (Courtesy Brunauer, Emmett and Teller.)... 

Uptake at saturation by a ferric oxide gel at 25°C, calculated as a volume of liquid (v,)... 

Fig. 4.25 Adsorption isotherms showing low-pressure hysteresis, (a) Carbon tetrachloride at 20°C on unactivated polyacrylonitrile carbon Curves A and B are the desorption branches of the isotherms of the sample after heat treatment at 900°C and 2700°C respectively Curve C is the common adsorption branch (b) water at 22°C on stannic oxide gel heated to SOO C (c) krypton at 77-4 K on exfoliated graphite (d) ethyl chloride at 6°C on porous glass. (Redrawn from the diagrams in the original papers, with omission of experimental points.)...

Wet preparation of red iron oxides can involve either a hydrothermal process (see Hydrothermal processing) or a direct precipitation and growth of iron oxide particles on specially prepared nucleating seeds of Fe202- In the hydrothermal process, iron(II) salt is chemically oxidized to iron(III) salt, which is further treated by alkahes to precipitate a hydrated iron(III) oxide gel. The gel can be dehydrated to anhydrous hematite under pressure at a temperature around 150°C. 

Gold purple, often caHed Purple of Cassius, is a tin oxide gel colored by finely divided gold (7). It has good coverage and brilliance in low temperature coatings such as porcelain enamels. It is a very expensive pigment, because of its difficult preparation as well as the price of gold. 

This concept may be invoked to account for electrolyte formation in microcracks in a metal surface or in the re-entrant angle formed by a dust particle and the metal surface. More importantly, it can also explain electrolyte formation in the pores of corrosion product and hence the secondary critical humidity discussed earlier. Ferric oxide gel is known to exhibit capillary condensation characteristic and pore sizes deduced from measurements of its adsorptive capacity are of the right order of magnitude to explain a secondary critical relative humidity as70 7o for rusted steel . 

Oil and hydrocarbon leaks that return with the condensate coat heat-exchange surfaces and cause FW system fouling and deposit binding. These materials must be removed or they will reenter the boiler to produce nonwettable boiler surfaces, and create serious problems. Oil in condensate should be removed by the use of an inline pre-coat filter. The pre-coating should be either aluminum hydroxide ox ferric hydroxide becaue both these hydrous oxide gels have an affinity for oil. 

The concentration of an oxidative gel breaker can be measured by colorimetric methods, by periodically or continuously sampling the gel [341]. The colorimetric reagent is sensitive to oxidizing agents. It contains iron ions and thiocyanate. Thus the quantity of breaker added to the fracturing fluid can be controlled. 

Among the oxidative breakers, alkali, metal hypochlorites, and inorganic and organic peroxides have been described in literature. These materials degrade the polymer chains by oxidative mechanisms. Carboxymethylcellulose, guar gum, or partially hydrolyzed polyacrylamides were used for testing a series of oxidative gel breakers in a laboratory study [180]. 

Perphosphate esters (e.g., methyl or ethyl esters) or amides can be used for oxidative gel breaking [1066]. Whereas the salts of the perphosphate ion interfere with the action of the crosslinkers, the esters and amides of perphosphate do not. Fracturing fluids that contain these breakers are useful for fracturing... 

B. Dewprashad. Method of producing coated proppants compatible with oxidizing gel breakers. Patent US 5420174, 1995. 

Guttman, A., Shieh, P, Lindahl, J., and Cooke, N., Capillary sodium dodecyl sulfate gel electrophoresis of proteins. II. On the Ferguson method of polyethylene oxide gels, /. Chromatogr., 676, 227, 1994. 

Miyazaki, T., Kim, H.-M., Kokubo, T., Ohtsuki, C. and Nakamura, T. (2001) Apatite-forming ability of niobium oxide gels in a simulated body fluid. Journal of the Ceramic Society ofJapan, 109, 929-933. 

Stachs O., Gerber Th., Petkov V., The structure formation of Zirconium oxide gels in alcoholic solutions, J. Sol-GelSci. Technol. 1999 15 23-30. 

Fig. 30. Spectra of three high area, amorphous, hydrous oxides of titanium compared with that of the crystalhne anhydrous oxide, rutile. One is a straight titania gel, two are coprecipitated with different elements to form mixed metal hydrous oxide gels.

This band is at a lower frequenqf than that of the Si-O stretch in pure Si oxide gel (1080 cm ) probably because the Si-O stretch is influenced by neighbouring Fe atoms. For adsorbed arsenate and selenate on ferrihydrite, Harrison Berkheiser (1982) reported a poorly resolved doublet at 805 and 875 cm , and weak bands at 700 cm and at 820, 880 and 910 cm respectively. These were attributed to splitting of the fundamental v vibration. 

Adsorption of alkaline earth, transition, and heavy metal cations by hydrous oxide gels of iron and aluminum. Soil Sci. Soc. Am. J. 40 796-799... 

Mechanisms of phosphate sorption by soils and hydrous ferric oxide gel. J. Soil Sd. 

Formula Cr(0H)3 3H20 MW 157.06 occurs only as hydrates Synonyms chromic hydroxide chromic oxide hydrous chromic oxide gel chromium hydrate chromic hydrate. 

Chromic oxide gel, chromium on aluminum, nickel-aluminum oxide Phosphoric acid on kieselguhr... 

Film Appearance. It is important to minimize film imperfections or defects when LDPE is blown into film. The common defects are arrow-heads, pinpoint gels, gels or fish eyes , and oxidized gels or colored specks. 

Inorganic oxopolymers can easily be generated in situ inside a soluble organic polymer as well as an organic component can easily be introduced into the oxide gels on simultaneous dissolution of the organic substances and the alkoxides. Both approaches lead to the formation of amorphous composites. 

Type IV isotherms (e.g. benzene on iron(III) oxide gel at 320 K) level off near the saturation vapour pressure and are considered to reflect capillary condensation in porous solids, the effective pore... 

Carbon tetrafluoride, 1 34 3 178 Carbon tetraiodide, 3 37 Carbonyl azide, formation of, by carbohydrazide, 4 35 Carbonyl fluoride, 6 155 Carbonyls, metal, 2 229 metal, nomenclature of, 2 264 structure of, 2 232 Catalysts, beryllium chloride, 5 25 boron fluoride, 1 23 chromium(III) oxide gel, 2 190... 

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