Gelatinization reversible

A white gelatinous precipitate of aluminium hydroxide is obtained when an alkali is added to an aqueous solution of an aluminium salt. Addition of an excess of caustic alkali causes the precipitate to redissolve, the whole process being reversed by the addition of a strong acid the actual substance present at any time depending on... 

Uses of gelatin are based on its combination of properties reversible gel-to-sol transition of aqueous solution viscosity of warm aqueous solutions abUity to act as a protective coUoid water permeabUity and insolubUity in cold water, but complete solubUity in hot water. It is also nutritious. These properties are utilized in the food, pharmaceutical, and photographic industries. In addition, gelatin forms strong, uniform, clear, moderately flexible coatings which readily sweU and absorb water and are ideal for the manufacture of photographic films and pharmaceutical capsules. 

Subtractive dye precursors (couplers) that could be immobilized in each of the silver containing layers were sought, so that dye formation in all layers could proceed simultaneously rather than successively. The first of these to be commercialized were in Agfacolor Neue and Ansco Color films, introduced soon after Kodachrome film. These reversal working films contained colorless couplers that were immobilized (ballasted) by the attachment of long paraffinic chains. The addition of sulfonic or carboxyUc acid groups provided the necessary hydrophilicity to make them dispersible as micelles in aqueous gelatin. 

Observations on the polymerization of readily polymerizable vinyl monomers such as styrene, vinyl chloride, and butadiene date back approximately to the first recorded isolation of the monomer in each case. Simon 2 reported in 1839 the conversion of styrene to a gelatinous mass, and Berthelot applied the term polymerization to the process in 1866. Bouchardat polymerized isoprene to a rubberlike substance. Depolymerization of a vinyl polymer to its monomer (and other products as well) by heating at elevated temperatures was frequently noted. Lemoine thought that these transformations of styrene could be likened to a reversible dissociation, a commonly held view. While the terms polymerization and depolymerization were quite generally applied in this sense, the constitution of the polymers was almost completely unknown. 

Peniche-Covas, C. A. L., Dev, S. B., Gordon, M., Judd, M. Kajiwara, K. (1974). The critically branched state in covalent synthetic systems and the reversible gelation of gelatin. In Gels and Gelling Processes. Faraday Discussions of the Chemical Society, No. 57, pp. 165-80. 

The property of thermal, reversible gelation is obtained by the addition of water-soluble proteins and protein degradation products to an aqueous solution of poly (vinyl alcohol) 2). Protein products such as albumin, gelatin, glue, a-amino acids, and their condensation products—diketopiperazines—may be used. A typical formulation for the preparation of a thermally reversible gel is ... 

Gelling agents under appropriate conditions self-associate to produce a three-dimensional structure. Some gelling, as with gelatine, is thermo-reversible while others, such as with high methoxyl pectin, is irreversible. Apart from the effects on the texture of the product an irreversible gelling agent is more of a problem in the factory since it cannot readily be recycled. 

Wu et al. [183] studied the reversible hydrolysis of penicillin G into 6-aminopeni-cillanic acid (6-APA) and phenylacetic acid (PAA) in a chromatographic reactor. E. coli cells containing penicillin acylase (the catalyst) were immobilized by entrapment into gelatine and further cross-linking with glutaraldehyde. The ad-... 

The gel of gelatine differs from that of silica in that in the former the sol-gel transformation is reversible and not in the latter. The coalescence of the amicrons of gelatine to form streptococcic fibrils occurs at low temperatures, a process readily reversed by elevation of the temperature which decreases the amount of adsorbed water, increases the mobility of the fibrils, and permits of their rupture into smaller units. Gelatine is thus readily rendered more disperse by water. 

Glycosyltransferases are also used extensively to modify natural polysaccharides. Thermoreversible gels that retrograded reversibly - comparable to gelatin... 

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