Physical and chemical interactions in pH-induced aggregation and gelation of whey proteins

This research investigates and evaluates the optical, physical, and chemical interactions between a diammonium hydrogen phosphate (DAP) solution and seven pigments commonly encountered in archaeological and historic fresco and secco wall paintings and polychrome monuments. The pigments include cinnabar, French ochre, chalk, lapis lazuli, raw sienna, burnt umber, and red lead. The raw pigments were analyzed before and after the interaction with the DAP solution, and the reaction products resulting from the contact of the pigments with the DAP solution were evaluated to obtain a comprehensive understanding of the effects of diammonium phosphate on the color, morphology, and chemical composition of the pigments. The results indicated no significant changes of the color or of the chemistry of cinnabar, French ochre, and lapis lazuli. Carbonate-containing primary and secondary (found as impurities in earth pigments) pigments, such as chalk and calcium carbonate, were transformed into calcium phosphate, though without a significant change in color. Phase and strong color changes occurred only for the red lead pigment, associated with the transformation of red lead into hydroxypyromorphite. These data established the parameters and identified the risks of the direct application of DAP solutions on pigments. Further research will be undertaken to assess the potential use of DAP as a consolidant of wall paintings and other polychrome surfaces through testing on wall painting/polychromy mockups and on-site archaeological/historic painted surfaces.

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A generalized approach to the description of interaction boundaries in migrating systems

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1965.0073 ◽

1965 ◽

Vol 163 (992) ◽

pp. 343-368 ◽

Cited By ~ 19

Keyword(s):

Moving Boundary ◽

Migration Pattern ◽

Chemical Interactions ◽

Boundary Equation ◽

Migration Patterns ◽

Simplified Approach ◽

Constituent Species ◽

Physical Interactions ◽

Total Composition ◽

Physical And Chemical

Patterns observed in the migration of a system of n solutes, where n ⋟ 1, are affected by the operation of either physical or chemical interactions or both. The effects of the two types of interactions have previously been considered separately by widely different approaches, leading in certain instances to the complete description of migration patterns. In the present work a unified and simplified approach is presented, which permits a complete mathematical description of all features of the migration pattern, provided the dependence of constituent velocities on total composition is defined for each constituent species. Emphasis is given to systems involving one or two migrating solutes. In particular, criteria have been established for sharp, spread and hypersharp boundary forms. The treatment, in common with some previous approaches, neglects the effects of diffusional spreading, and considers only time-independent interactions. The general theory is first illustrated with chemically associating systems, and the examples include descriptions of cases involving two solutes, which have been previously explained by physical argument alone. The operation of physical interactions is also treated by the theory, both by selecting appropriate models and by introducing general functions. Finally, the moving boundary equation is applied to selected migration patterns, modified by both physical and chemical interactions.

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