Dissolution of solids

Batch Stirred Tanks Tanks agitated by coaxial impellers (turbines, paddles, or propellers) are commonly used for batch dissolution of solids in liquids and may be used for leaching fine solids. Insofar as the controlhng rate in the mass transfer is the rate of transfer of mate-... 

Among the various mechanisms that have been proposed for the dissolution of solids [101,102], two of the simplest are depicted in Fig. 15. The common features of these are that an infinitesimally thin film of saturated solution of concentration cs (the solubility) is formed at the solid-liquid interface and that in the well-mixed bulk of solution, the concentration of the dissolving solid at any given time is cb. 

Fig. 15 Two of the simplest theories for the dissolution of solids (A) the interfacial barrier model, and (B) the diffusion layer model, in the simple form of Nemst [105] and Brunner [106] (dashed trace) and in the more exact form of Levich [104] (solid trace). c is the concentration of the dissolving solid, cs is the solubility, cb is the concentration in the bulk solution, and x is the distance from the solid-liquid interface of thickness h or 8, depending on how it is defined. (Reproduced with permission of the copyright owner, John Wiley and Sons, Inc., from Ref. 1, p. 478.)...

The chloride content of groundwater may be a sensitive indicator of either the distance between the intake area of the aquifer and coast or the amount of evapotranspiration prior to groundwater recharge. Because chloride is not normally derived from dissolution of solid aquifer materials and it does not enter into ion exchange reactions to any great extent, the chloride content in shallow aquifers and aquifers isolated from sources of connate water should reflect some of the original environmental factors of the outcrop area [19,86]. 

Finally, we assume no precipitation and no dissolution of solid phases. Closed system and mass conservation imply... 

It is interesting to note that many crystal poisons not only interfer with nucleation and the growth of crystals but may also retard their dissolution. As we have seen (Chapter 6), precipitation and dissolution of solids proceed by the attachment or detachment of ions most favorably at kink sites of the crystalline surface. Solutes such as organic substances, or phosphates may upon adsorption immobilize kinks and thus retard dissolution. 

Studies on the dissolution of solids in the liquid phase include that of Hixson and Baum(74) whose correlation of data in terms of Reynolds, Sherwood and Schmidt numbers, discussed in detail in Section 10.2 in connection with mass transfer during leaching, is one of the most frequently used methods for calculating the mass transfer coefficient for the solid dissolution. 

Type of solution (aqueous vs. lipid) Rate of dissolution of solid drugs Concentrations of a drug present Blood flow to the site of absorption Surface area of absorption... 

Iron(II) and (III) cyano complexes provide very interesting mechanistic chemistry. The Fe(CN)5H20 ion is a popular substrate for study. It is easily prepared in situ by the dissolution of solid Na3[Fe(CN)jNH3] for 15 minutes at 25°C in aqueous solution. For a large variety of entering groups Y (unspecified charge) a D mechanism is favored (Prob. 18) ... 

In crystallization a solid is formed fi om a supersaturated solution, fiequently with chemical reactions such as formation of complex crystals from ions in the solution. The dissolution of solids is the reverse of crystallization. We can write this process as... 

Ryan et al. (2001) studied the effects of hydroxyapatite addition to soils impacted by Pb from smelter operations. Dialysis experiment were conducted where the soil and hydroxyapatite solids were placed in separate dialysis bags suspended in 0.01 M NaN03. Chloropyromor-phite formed on the dialysis membrane containing the soil. The dissolution of solid-phase soil Pb was the rate-limiting step for pyromorphite formation. EXAFS showed that after the 240 day incubation the hydroxyapatite treatment caused a change in the average, local molecular bonding environment of soil Pb. 

In voltammetric experiments, electroactive species in solution are transported to the surface of the electrodes where they undergo charge transfer processes. In the most simple of cases, electron-transfer processes behave reversibly, and diffusion in solution acts as a rate-determining step. However, in most cases, the voltammetric pattern becomes more complicated. The main reasons for causing deviations from reversible behavior include (i) a slow kinetics of interfacial electron transfer, (ii) the presence of parallel chemical reactions in the solution phase, (iii) and the occurrence of surface effects such as gas evolution and/or adsorption/desorption and/or formation/dissolution of solid deposits. Further, voltammetric curves can be distorted by uncompensated ohmic drops and capacitive effects in the cell [81-83]. 

DVakova, M. K., Production of Synthetic Liquid Fuels and Chemical Products by Thermal Dissolution of Solid Fuels, p. 86, Academy of Science of the U.S.S.R., 1957. 

Compound 25 (R1 = H 2.7 g, 7.3 mmol) was suspended in EtOAc (20 mL). Ethereal CH2N2 soln was added dropwise to the suspension until complete dissolution of solid material occurred and the solution turned slightly yellow. Concentration of the mixture afforded a viscous oil yield 2.9 g (quantitative). 

Because both the Ag+ andCr042- ions come from dissolution of solid Ag2Cr04, [Ag + ] must be twice [Cr042- ]. Substituting [ Ag + ] and [Cr042- ] into the equilibrium equation gives the value of Ksp. 

Yonezawa, Y., Kawase, S., Sasaki, M., Shinohara, I., and Sunada, H. (1995) Dissolution of solid dosage form. V. New form equations for non-sink dissolution of a monodisperse sySfeBip. Pharm. Bull, 43 304-310. 

Suzuki, FI. and FI. Sunada. 1998. Some factors in uencing the dissolution of solid dispersions with nicotinamide and hydroxypropylmethylcellulose as combined carriQIsem Pharm Bull 46 1015-1020. 

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