Periodic precipitation

N. Curtis, D. G. Leaist. Interdiffusion of aqueous silver nitrate and potassium chromate and the periodic precipitation of silver chromate Liesegang bands. Ber Bunsen-Ges—Phys Chem, Chem Phys 702 164, 1998. 

Imai, H., Tatara, S., Furuichi, K. and Oaki, Y. (2003) Formation of calcium phosphate having a hierarchically laminated architecture through periodic precipitation in organic gel. Chemical Communications, 1952—1953. 

Thomson-Freundlich equation relates the solubility of a particle to its curvature radius (e.g., Swalin, 1962). Using this equation, Kirkaldy and Young (1987) show how periodic precipitation may result from the capillary resistance of the matrix to grow small precipitates. Formally, the conditions read... 

Flicker, M. Ross, J. (1974). Mechanism of chemical instability for periodic precipitation phenomena. J. Chem. Phys., 60, 3458-65. 

Wagner, C. (1950). Mathematical analysis of the formation of periodic precipitation. J. Coll. 

Fig. 9. Liesegang ring periodic precipitation in Pbl2. The dark regions are yellow rings of...

Winter precipitation was collected in Warren, MI over a four-year period. Precipitation was classified as rain, snow, or mixed rain and snow based on the Local Climatological Data from Detroit Metropolitan Airport. The volume-weighted mean concentrations are shown in Table I. The weighted standard deviations were calculated as... 

Various theories have been advanced in explanation. Ostwald suggested that supersaturation took place, followed by precipitation, which cleared the immediate neighbourhood of the reactants, and it was therefore necessary for the silver nitrate to diffuse further before supersaturation was again reached. Hatsehek, however, shows that the periodic precipitation takes place in conditions which render supersaturation impossible. Williams and Mackenzie maintain that the silver chromate is precipitated according to the usual rules of the solubility product, and does not behave in any way as a protected colloid but as a crystalloid. More recent w ork suggests that whenever precipitation takes place, the precipitate first passes through the colloidal... 

Quartz silica sand of high purity is used as the most important source of silica and glass in industry, although most of them are coarse granules and difficult to dissolve in the alkali solution at normal pressure. The jewel stone opal is made of very densely packed periodic precipitate of monodispersed silica particles. 

Chemical reactions are propagated in space as well as in time. Flames and explosions travel with definite speeds, new phases grow, and interdififusion phenomena may lead to periodic precipitation effects. 

Mechanisms of formation of rhenium(I), -(III), -(IV), and -(V) complexes with bidentate Schiff bases have been discussed in relation to available structural data. This discussion includes a few qualitative comments on reactivities.The course of substitution at [ReBr ] " in aqueous hydrochloric acid, and at [ReClg] in hydrobromic acid, was monitored by periodic precipitation by Cs and identification of the solids produced. Species identified are shown in equations (2) and (3). These observations demonstrate the important role played by the effect... 

Two-dimensional experiments [59] on periodic precipitation of PbCr04, CuCr04 and Hgl2 have been carried out with a simple and inexpensive Das-Pushkarna-Lall (DPL) flow reactor [60]. 

Lead chromate is another photosensitive material which invoked many workers to carry out detailed investigation. Hatschek [68] and Das et al. [69] reported results of the light-induced periodic precipitation of lead chromate in agar-agar gel medium. In order to study the effect of light on pattern formation, experiments were done both in the presence of sunlight and in complete darkness. Homogeneous precipitation was observed when the experiment was performed in complete darkness while rhythmicity was observed in an illuminated condition. 

Kai, S., Muller, S.C., and Ross, J., Measurements of temporal and spatial sequences of events in periodic precipitation processes, J. Chem. Phys., 76, 1392, 1982. Kenning, D.B.R., Two-phase flow with nonuniform surface tension, Appl. Mech. Rev., 21, 1101, 1968. 

Klueh, R.L. and Mullins, W.W., Periodic precipitation (Liesegang phenomenon) in solid silver II. Modification of Wagner s mathematical analysis, Acto Met, 17,69,1969. Knapp, R. and Aris, R., On the equations for the movement and deformation of a reaction front. Arch. Rat Mech. Anal, 44, 165, 1972. 

A variety of spatial structures such as chemical fronts or waves, periodic precipitates and regular spatial patterns at liquid interfaces have begun to be investigated since the first experiments on the formation of chemical spatial... 

Periodic precipitation phenomena, commonly called Liesegang rings, have been studied for a long time. According to recent experimental results (Kai et al., 1982 Muller et al., 1982) patterned precipitation is a postnucleation phenomenon which occurs after a continuous distribution of colloid has been established. The phenomenon can be described at least formally by an instability mechanism based on the autocatalytic growth of colloid particles with diffusion (Ross, 1985). 

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