Dissolution constants

Kw ionic product of water Ka = dissolution constant of weak acid ... 

Broecker and Peng, p. 59 dlsscon = 7 dissolution constant in DJSS pcpcon = / carbonate precipitation constant disfac -. 01 scaling factor in dissolution rate eole/e 3/y delcorg 10 Fractionation by photosynthetic organises dcse = 2 Delta 13C Isotope ratio for sea eater, per eil... 

Rate of the photochemical reductive dissolution of hematite, = d[Fe(II)]/dt, in the presence of oxalate as a function of the wavelength at constant incident light intensity (I0 = 1000 peinsteins "1 lr1). The hematite suspensions were deaerated initial oxalate concentration = 3.3 mM pH = 3. (In order to keep the rate of the thermal dissolution constant, a high enough concentration or iron(II), [Fe2+] = 0.15 mM, was added to the suspensions from the beginning. Thus, the rates correspond to dissolution rates due to the surface photoredox process). 

It is interesting, however, to compare the different dissolution constants. K, obtained with the simple Langmuir isotherm model with experimental data of dissolution rates over a 24-hour period. Figure 15 gives concentrations obtained consecutively with fresh solvent every 24... 

Freed, V.H. (1976) Solubility, hydrolysis, dissolution constants and other constants of benchmark pesticides. In A Literature Survey of Benchmark Pesticides. George Washington University Medical Center, Washington, DC. 

As may be seen from Eq. 6.8, the Gibbs free energy, G, is the most important thermodynamic parameter in describing chemical reactions, because it represents the moles of the constituents participating in the reaction, and how a chemical reaction changes the number of moles. Dependence of a chemical reaction on thermodynamic parameters, such as the temperature and pressure, is best represented by AG in an Arrhenius type of equation for the dissolution constant K... 

Sverdrup (1990) and Sverdrup and Warfvinge (1995) developed Ae PROFILE model to calculate mineral weathering rates by means of a geochemical mass-balance procedure. This model differs from the others in that it uses dissolution constants, which were, for the most part, determined in the laboratory. Empirical fitting parameters, such as surface area of mineral exposed, are used to adjust the model to the real system being described. The model appears to work satisfactorily in many catchments if the fitting parameters are chosen judiciously. This requires a considerable amount of knowledge... 

Jacobson, R. L. 1973. Controls on the quality of some carbonate ground waters Dissolution constants of calcite and CaHCOj from 0 to 50°C. PhD thesis, The Pennsylvania State Univ., University Park, PA. 

Reardon, E. J. 1975. Dissolution constants of some monovalent sulfate ion pairs at 25°C from stoichiometric activity coefficients. J. Phy.s. Chem. 79 422. 

In a very early study Patat (1945) investigated the hydrolysis of aniline to phenol in a water-based acidic solution in near-critical and supercritical water (Tc = 374.2°C, Pc = 220.5 bar). Phosphoric acid and its salts are used as the catalyst for this reaction. The reaction proceeds extremely slowly under normal conditions and reaches equilibrium at low conversion levels. For these reasons, Patat chooses to study the reaction in supercritical water to temperatures of 450°C and to pressures of 700 bar in a flow reactor. He finds that the reaction follows known, regular kinetics in the entire temperature and pressure space studied and the activation energy of the hydrolysis (approximately 40 kcal/mol) is the same in the supercritical as well as in the subcritical water. He suggests that the reaction is catalyzed by hydrogen ions formed from dissolution of phosphoric acid in supercritical steam. Very small amounts of phosphoric acid and the salts of the phosphoric acid are dissolved in the supercritical steam and are split into ions. Patat lists several dissolution constants for primary ammonium phosphates in supercritical steam. In this instance, the reaction performance is improved when the reaction is operated homogeneously in the mixture critical region and, thus, in intimate contact between the reactants and the catalyst. 

A complete description of any groundwater system necessitates consideration of reactions between rock forming minerals and the aqueous phase. This cannot be achieved without accurate thermodynamic properties of both the participating aluminosilicate minerals and aqueous aluminum species. Most computer codes used to calculate the distribution of species in the aqueous phase utilize the "reaction constant" approach as opposed to the "Gibbs free energy minimization" approach (3). In the former, aluminosilicate dissolution constants are usually written in terms of the aqueous aluminum species, Al, which is related to other aqueous aluminum species by appropriate dissociation reactions. 

Figure 4. Plots of log Ks4 versus the reciprocal of absolute temperature, comparing the corresponding dissolution constants for bayerite, gibbsite, boehmite, diaspore and corundum. The experimental precision of the plotted solubility measurements produces a maximum 2o uncertainty of < 0.2 in log Ks4 and < 4K in temperature.

Table IV summarizes log Kj4 values for aluminum hydroxides and oxyhydroxides, and corundum between 0 and 350 C. They were calculated using the modified H.K.F. equation of state (70) together with the data given in Tables I and II. These values are suitable for incorporation into distribution of species codes such as EQ3 (67), provided that A1(0H)4 (or AIO2) is made a basis species. Calculation of dissolution constants for other aluminosilicates can be made using the Gibbs free energy data for Al(OH)4 or AIO2 Provided in Table II.

Potentiometric H2O Krebs HA and Speakman JC, Dissolution constant, solubility and the... 

Example 1.3 Calculating the dissolution constant of calcite at 10 °C from the following enthalpies and free enthalpies of formation (in kJ-mole ... 

Published dissolution constants of dolomite are within a range of 10" to 10 -. Sherman and Barak (2000) recommend value equal to 17.2. 

M is the time-dependent undissolved (solid) drug amount present in the donor compartment S is the area available for permeation K, is the drug dissolution constant Cj is the drug solubility Vr is the receiver compartment volume Ai, A3, and A2 are, respectively, the thicknesses of the first and the second stagnant layers and the membrane Cjo and Mg are, respectively, the initial drug concentration and undissolved drug amount in donor compartment, while K2X, K22, and K r are partition coefficients defined as follows ... 

Fig. 3.3 Logarithm of the dissolution constant, k (oxygen gram atom cm s ), plotted against the reciprocal of temperature (K ). The data are for near-neutral pH solutions. The dashed line gives the rate constant proposed by Wood and Walther (1983). The solid lines give the rate constants for the compensation law proposed in the text constructed for log k of — 12, —14, —15, -17 at 25 °C (Wood and Walther 1983)...

Bjerrum, N. and Unmack, A. (1929) Electrometric measurements with the hydrogen electrode on mixtures of acids and bases with salts. The dissolution constants of water, phosphoric acid, citric acid and glycine. Kgl. Danske Videnskab. Selskah, Mat.-fys. Medd., 9, 5-206. 

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