Gelatinous surface layer

The formation of a gelatinous surface layer Such a layer immobilizes the liquid inside the film between two adjacent bubbles so that gravitational and capillary stresses are insufficient to cause flow. The gelatinous surface layer is formed by chemical or inter-molecular interactions occurring in the film. 

Gelatinous surface layers are formed due to the presence of some impurity in the liquid that interacts with the liquid to form a hydrous gel structure, extending from the surface to a depth of about 900 A. The liquid makes up the main portion of the surface film (at least 97 percent by weight). The liquid is oriented and partly immobilized in an icelike configuration which acts as the linkage between solute molecules. 

In view of the fundamental importance of the Gibbs-Thomson formula, and the magnitude of the discrepancies between the figures calculated from it and the experimental results, it is of obvious interest to inquire to What causes the deviations may be due. The first point to be noticed is that the complex substances which exhibit them most markedly form, at least at higher concentrations, colloidal and not true solutions. It is, therefore, very probable that they may form gelatinous or semi-solid skins on the adsorbent surface, in which the concentration may be very great. There is a considerable amount of evidence to support this view. Thus Lewis finds that, if the thickness of the surface layer be taken as equal to the radius of molecular attraction, say 2 X io 7 cms., and the concentration calculated from the observed adsorption, it is found, for instance, for methyl orange, to be about 39%, whereas the solubility of the substance is only about 078%. The surface layer, therefore, cannot possibly consist of a more concentrated solution of the dye, which is the only case that can be dealt with theoretically, but must be formed of a semi-solid deposit. 

The annealed surface layer may be stabilized by lateral association with those hemicelluloses that bond strongly to the microfibrils. Also in the G-layer, which is mostly cellulose, the presence of any (uncertain) hemicelluloses and the layer s strongly hydrated nature (gelatinous implies a gel) must prevent strong lateral bonding of the individual microfibrils to form larger macrofibrils. 

Analytically important enzymes present in microbial cells may often be utilized without further purification. The cells are easily harvested and immobilized on the surface of a sensor by a simple attachment using dialysis membrane, entrapment into gel (agar, collagen, gelatin, etc.) layers, adsorption on filter paper or other supports and only rarely covalently bound. Riedel [186] gives in his review paper characteristics... 

Other uses in photography involve silica-hardened gelatin surfaces on X-ray film (726), colloidal silica-modified silver halide emulsions for higher sensitivity (727), and silica-polyvinyl alcohol as a replacement for gelatin in image-receiving layers (728). 

According to Homyak et al. (17), the electropolished aluminum is rinsed immediately in distilled water (often with the aid of a strong stream of distilled water to remove the tenacious gelatinous oxide layer), immersed in concentrated nitric acid for 10 min, rinsed and left to dry in air. Well-polished aluminum should present a shiny/mirror-like surface accurate polishing is crucial for obtaining high-quality aluminum oxide membranes. 

They have the same effect as agglomerating bacteria (gelatinous deposits) and in addition attack wood (cooling tower). They form a gelatinous blackish layer on wet surfaces. 

The adhesion between two solid particles has been treated. In addition to van der Waals forces, there can be an important electrostatic contribution due to charging of the particles on separation [76]. The adhesion of hematite particles to stainless steel in aqueous media increased with increasing ionic strength, contrary to intuition for like-charged surfaces, but explainable in terms of electrical double-layer theory [77,78]. Hematite particles appear to form physical bonds with glass surfaces and chemical bonds when adhering to gelatin [79]. 

---