Rate of dissolving

The rate of dissolving of monolayers constitutes an interesting and often practically important topic. It affects, for example, the rate of loss of monolayer... 

The chemical reactivity of a self-similar surface should vary with its fractional dimension. Consider a reactive molecule that is approaching a surface to make a hit. Taking Fig. VII-6d as an illustration, it is evident that such a molecule can see only a fraction of the surface. The rate of dissolving of quartz in HF, for example, is proportional to where Dr, the reactive... 

A rather different method from the preceding is that based on the rate of dissolving of a soluble material. At any given temperature, one expects the initial dissolving rate to be proportional to the surface area, and an experimental verification of this expectation has been made in the case of rock salt (see Refs. 26,27). Here, both forward and reverse rates are important, and the rate expressions are... 

Although the rate of dissolving measurements do thus give a quantity identified as the total surface area, this area must include that of a film whose thickness is on the order of a few micrometers but basically is rather indeterminate. Areas determined by this procedure thus will not include microscopic roughness (or fractal nature). 

The rate of dissolving of a solid is determined by the rate of diffusion through a boundary layer of solution. Derive the equation for the net rate of dissolving. Take Co to be the saturation concentration and rf to be the effective thickness of the diffusion layer denote diffusion coefficient by . 

Make a numerical estimate, with an explanation of the assumptions involved, of the specific surface area that would be found by (a) a rate of dissolving study, (b) Harkins and Jura, who find that at the adsorption of water vapor is 6.5 cm STP/g (and then proceed with a heat of immersion measurement), and (c) a measurement of the permeability to liquid flow through a compacted plug of the powder. 

Of concern is that there is very little information often available concerning the effects of common waste waters on evaporation rates. As noted, the evaporation rate of a solution will decrease as the solids and chemical concentrations increase. However, the overall effects on evaporation rates of dissolved constituents as well as color changes and other factors of wastewater are largely unknown. 

L se-gef s, n. dissolving vessel, -geschwiadig-keit, /. rate of dissolving, -kraft, /. solvent power. 

More directly related to turbulence and motion at the interface. Includes scale-up for rate of dissolving of solids or mass transfer between liquid phases. Using geometric similarity and equal power per volume results in same n value. 

One of the factors that influences the rate of dissolving of solid is the area, A, of the crystal surface that contacts the liquid. If many crystals (with large A) are dissolving simultaneously, the rate of dissolving is faster than if only a few crystals (with small A) are in the solvent. The rate of dissolving is proportional to this liquid-solid surface area, A. 

Thus, by expressing the dynamic balance between the rates of dissolving and precipitation, we obtain (4). The concentration of I2 at equilibrium is a constant, fixed by the temperature. This constant equals the solubility. 

In view of the discussion of the factors that determine the rate of dissolving (Section 10-1.2), propose two methods for increasing the rate at which sugar dissolves in water. 

If the surface complex is the chromophore, then the photochemical reductive dissolution occurs as a unimolecular process alternatively, if the bulk iron(III)(hydr)-oxide is the chromophore, then it is a bimolecular process. Irrespective of whether the surface complex or the bulk iron(IIl)(hydr)oxide acts as the chromophore, the rate of dissolved iron(II) formation depends on the surface concentration of the specifically adsorbed electron donor e.g. compare Eqs. (10.11) and (10.18). It has been shown experimentally with various electron donors that the rate of dissolved iron(II) formation under the influence of light is a Langmuir-type function of the dissolved electron donor concentration (Waite, 1986). 

As more ions enter the solution, the rate of the reverse change, recrystallisation, increases. Eventually, the rate of recrystallisation becomes equal to the rate of dissolving. As you know, when the forward rate and the backward rate of a process are equal, the system is at equilibrium. Because the reactants and the products are in different phases, the reaction is said to have reached heterogeneous equilibrium. For solubility systems of sparingly soluble ionic compounds, equilibrium exists between the solid ionic compound and its dissociated ions in solution. 

Miller, G. C., and R. G. Zepp, Effects of suspended sediments on photolysis rates of dissolved pollutants , Water Res., 13, 453-459 (1979b). 

The technique has drawbacks associated with the establishment of equilibrium between the gas and the other phase, typically a liquid. If the gas is a reactant, its rate of dissolving in the liquid phase should be faster than the chemical rate-determining step. If it is a product, its release should be sufficiently fast that supersaturation in the liquid phase does not become a problem. (The relationships between rates of transport between phases and chemical processes are explored in Chapter 5.)... 

The conditions for maximal dissolving of borate in a mixture of sulfurous and phosphorous acids are investigated. The rate of dissolving borate (y) is controlled by varying these factors Xrtemperature of reaction, °C X2-reaction time, min X3-stoichio-metric ratio of phosphorous acid in per cent, % and X4-concentration of phosphorous acid as, % P205. 

RPR 200,735 is a weak base. Its conjugate acid has a pA"a of 5.3. Only strong acids are able to form a stable salt with RPR 200,735. Investigated acids include hydrochloric acid, hydrobromic acid, and methanesulfonic acid (Table 13.2). The methanesulfonate salt was found to be superior to the other salts in all aspects water solubility, hygroscopy (absorption of moisture from air), and rate of dissolving. Furthermore, the flow properties of the methanesulfonate salt facilitated capsule and tablet preparation. 

Kaiser, K., and W. Zech. 1998. Rates of dissolved organic matter release and sorption in forest soils. Soil Science 163 714—725. 

Kirchman, D. L., Y. Suzuki, C. Garside, and H. W. Ducklow. 1991. High turnover rates of dissolved organic carbon during a spring phytoplankton bloom. Nature 352 612-615. 

Since crushed basalt has been recommended as a major backfill component (1), experiments were completed to evaluate the rate of dissolved oxygen consumption and the redox conditions that develop in basalt-water systems under conditions similar to those expected in the near-field environment of a waste package. Two approaches to this problem were used in this study (l)the As(III)/As(V) redox couple as an indirect method of monitoring Eh and (2) the measurement of dissolved oxygen levels in solutions from hydrothermal experiments as a function of time. The first approach involves oxidation state determinations on trace levels of arsenic in solution (4-5) and provides an estimate of redox conditions over restricted intervals of time, depending on reaction rates and sensitivities of the analyses. The arsenic oxidation state approach also provides data at conditions that are more reducing than in solutions with detectable levels of dissolved oxygen. 

Example Multivariate cross-correlation for the computation of transport rates of dissolved metals in river water... 

Turekian, K.K., Tanaka, N., Turekian, V.C., Torgersen, T., and Deangelo, E.C. (1996) Transfer rates of dissolved tracers through estuaries based on 228Ra study of Long Island Sound. Cont. Shelf Res. 7, 863-873. 

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