Adsorptive power

On standing, gelatinous aluminium hydroxide, which may initially have even more water occluded than indicated above, is converted into a form insoluble in both acids and alkalis, which is probably a hydrated form of the oxide AI2O3. Both forms, however, have strong adsorptive power and will adsorb dyes, a property long used by the textile trade to dye rayon. The cloth is first impregnated with an aluminium salt (for example sulphate or acetate) when addition of a little alkali, such as sodium carbonate, causes aluminium hydroxide to deposit in the pores of the material. The presence of this aluminium hydroxide in the cloth helps the dye to bite by ad sorbing it—hence the name mordant (Latin mordere = to bite) dye process. 

Chromium(III) hydroxide, like aluminium hydroxide, possesses adsorptive power, and the use of ehromium compounds as mordants is due to this property. 

Zeolites as cracking catalysts are characterized hy higher activity and better selectivity toward middle distillates than amorphous silica-alumina catalysts. This is attrihuted to a greater acid sites density and a higher adsorption power for the reactants on the catalyst surface. 

In any particular case, the adsorption value depends on the properties of both the adsorbate (its adsorbability) and the adsorbent (its adsorptive power). Substances with enhanced adsorbability are called surface active. By convention, adsorption is regarded as insignificant when 0 < 0.1, and as significant when 0 > 0.5. 

The interactions between electrode metals and solvents are reflected in the adsorption and catalytic properties. The adsorption of other solution components (ions and neutral molecules other than the solvent) is attended by a displacement of adsorbed solvent molecules or their reorientation. Therefore, a metal s adsorptive power is low under conditions where its energy of interaction with the solvent is high. 

A platinum disk electrode was electrolytically platinized in a platinum chloride solution to increase the surface area and enhance the adsorption power. The platinized platinum electrode was then immersed in a solution containing 10 mg ml l ADH. 0.75 mM and 6.2 mM NAD. After sufficient adsorption of these molecules on the electrode surface, the electrode was transferred into a solution containing 0.1 M pyrrole and 1 M KC1. Electrochemical polymerization of pyrrole was conducted at +0.7 V vs. Ag/AgCl. The electrolysis was stopped at a total charge of 1 C cm 2. An enzyme-entrapped polypyrrole membrane was deposited on the electrode surface. 

As pointed out by Sposito (1984) this equation initiated the surface chemistry of naturally occurring solids. Maarten van Bemmelen published this equation (now referred to as the Freundlich isotherm) more than 100 years ago and distilled from his results, that the adsorptive power of ordinary soils depends on the colloidal silicates, humus, silica, and iron oxides they contain. 

It must be concluded that although the first layer of adsorbed molecules is held extremely tenaciously and that a large decrease in free energy occurs on the adsorption of a unimolecular layer of gas, a further but smaller decrease in free energy may take place on the further adsorption of gas in the secondary films. We would anticipate that a surface of feeble adsorptive power such as diamond would be almost completely saturated with a unimolecular layer, but active surfaces such as of metals are not completely saturated. 

Fuller s Earth. A variety of clay-like materials containing silicates of Fe and Mg which. have natural adsorptive powers have been used in industry for many putposes, among them as absorbent for NG in Dynamites Refs 1) Davis (1943) 195, 216, 218, 332 Bt 336 2) Fedoroff Clift 4(1946), 37 3) Cond-... 

Fuller s earth, also used as an adsorbent, is a parous colloidal aluminum silicate (clay> which has a high natural adsorptive power. See also Fnller s Earth. 

Diaiomite has only weak adsorption powers but shows excellent absorption because of its structure and high surface area. Acids, liquid fertilizers, alcohol, water, oils, and other fluids are absorbed by diatomite. 

DMePh from other ingredients of a mixt, a small amt of p-MNA may be added to the soln before it is run thru the column. As p-MNA is yel in color and as its adsorption power is the same as for DMePh, both compds would move thru the column as one yel zone visible thru the tube, thus indicating progress of analysis. Other methods of revealing the position of colorless zones are listed in Ref 58,p 57... 

A. Tiselius in 1940-43(Ref 58,p XX) and known as displacement analysis, the soln of sample introduced in the upper section of the column is continuously rinsed with a soln of a substance which possesses a stronger adsorption power than any of the sample components. 

Surface molecules with their polar groups buried are called endotropic , this is the normal stable position. Such surfaces have little reactivity or adsorptive power. Multilayer surfaces may be conditioned , the top... 

Multilayers of sterols,3 chlorophyll,4 and proteins5 have also been built. Those of sterols show specific adsorptive powers for digitonin, according to the stereochemical configuration of the hydroxyl group those of chlorophyll showed no fluorescence, although the quantity deposited was sufficient to give marked fluorescence in solution. 

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