Surface of foam

First, (Type A) an oil will neither spread over nor enter the surface of foam lamellae when E and S are less than zero. 

Secondly, (Type B) oil will enter but not spread over the surface of foam lamellae when E is greater than zero but S is less than zero. 

Thirdly, (Type C) oil will enter the surface of foam lamellae and then spread over the lamellae surfaces if both E and S are greater than zero. This latter behavior, typically, will destabilize the foam. 

An early study referred to the determination of traces of gold in ores by absorbing this element on the surface of foamed plastic [23], The sample containing the gold traces was first dissolved by a HC1-HN03 mixed solution and a piece of foamed plastic was then placed therein. After vibration for 30 min. on a vibrator, the solid material was removed, washed with tap water, and placed in a CL cell. A 2-mL volume of 1.0 mmol/L EDTA was added to the cell and the lid was closed then 2 mL of 0.01 mmol/L luminol solution was injected into... 

Cryogenic fluid transfer lines are generally classified as one of three types uninsulated, foam-insulated lines, and vacuum-insulated lines. The latter may entail vacuum insulation alone, evacuated powder insulation, or multilayer insulation. A vapor barrier must be applied to the outer surface of foam-insulated transfer lines to minimize the degradation of the insulation that occurs when water vapor and other condensables are permitted to diffuse through the insulation to the cold surface of the lines. 

The change in the specific surface of foams that decay in gravitational field can be expressed by either Eq. (6.16) or by the following relation, given in [54]... 

CD mix starch and water cook under pressure foam by pressure relief (T) shape and cut foam toast surface of foam dry the snacks (7) cool the snacks... 

Foams generally give good diffuse reflection spectra. However, the surface of foam products is often a continuous skin which may introduce a significant specular component into the spectrum. 

Shearer and Akers [5] allow for the possible presence of several drops of antifoam in a foam film by simply increasing the supposed spreading perimeter to 2%N(rj)rj p, where Mr ) is the number of drops per film which will be some function of the film radius r. If, however, the drops are evenly dispersed over the surface of foam films, then spreading will occur in opposing directions. Flow of liquid from the film will be less than that predicted if the spreading perimeter is simply increased to 2nN rj)r p. 

It is generally accepted that if oils, in the form of dispersed drops, have the potential to act as antifoams, they must be able to enter (or emerge into or adhere to ) the surfaces of foaming liquids. The classic entry coefficients, and E , should all therefore be... 

There appears to be a consensus that necessary properties of antifoam oils for aqueous foams include insolubility in surfactant solution and a tendency to emerge (or enter ) into the air-water surfaces of foam films. Here we review early work concerning the antifoam behavior of neat oils possessing these properties. Of particular interest is the interpretation of the observed behavior using the theories of antifoam mechanism outlined in Sections 4.4 and 4.5. 

Most commercially effective antifoams are oil based. The relevance of the entry and spreading behavior of such oils at the surfaces of foaming fluids to their antifoam function has been the subject of much debate over the past half centmy. A chapter is therefore specifically devoted to the entry and spreading behavior of oils and the role of thin film forces in determining that behavior. 

The chapter addresses the ordering of Si nanoparticles in thin liquid films. While hydrophilic Si nanoparticles order in the film core perpendicular to the outer film surfaces, partially hydrophobized Si particles can also adsorb at the (fiuid) surface of foam films or emulsion films. Lateral ordering becomes important for the stability of the respective macroscopic systems (foams and emulsions). 

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