Ionic crystals dissolution

Macpherson, J.V., Unwin, P.R., Hillier, A.C. and Bard, A.J. (1996) In-situ imaging of ionic crystal dissolution using an integrated electrochemical/AFM probe. Journal of the American Chemical Society, 118, 6445-6452. 

Another illustration of time-dependent FEM analysis is the use of SECCM (double-barrel ion conductance probe) to investigate ionic crystal dissolution. A transient Fick s diffusion equation. 

Kinnear, S. L. McKelvey, K. Snowden, M. E. Peruffo, M. Colburn, A. W Unwin, P. R. 2014. Dualbarrel conductance micropipet as a new approach to the study of ionic crystal dissolution kinetics. 

FIGURE 13.14 SECM arrangement for the study of ionic crystal dissolution using copper sulfate pen-tahydrate as an example substrate in contact with a saturated solution of copper sulfate. (Adapted from Macpherson, J.V. and Unwin, P.R., J. Phys. Chem., 98,1704, 1994.)... 

Molecular Aspects on the Dissolution and Nucleation of Ionic Crystals in Water... 

Water is the most common solvent used to dissolve ionic compounds. Principally, the reasons for dissolution of ionic crystals in water are two. Not stated in any order of sequence of importance, the first one maybe mentioned as the weakening of the electrostatic forces of attraction in an ionic crystal known, and the effect may be alternatively be expressed as the consequence of the presence of highly polar water molecules. The high dielectric constant of water implies that the attractive forces between the cations and anions in an ionic salt come down by a factor of 80 when water happens to be the leaching medium. The second responsible factor is the tendency of the ionic crystals to hydrate. 

The composition and properties of the ions contained in the solution are not the same as those of ions contained in the ionic crystal lattice. It is already known that anhydrous copper sulfate (CuS04) is colorless. This implies that Cu2+ and SCT ions that make up the crystal lattice of the sulfate are colorless. When the Cu2+ ions combine with water molecules during dissolution they turn blue (the color characteristic of copper salt). This color is therefore due to hydrated ions of copper, i.e., ions connected with the water molecules. 

One method of introducing ions into solution is by the dissolution of an ionic crystal (e.g., NaCl). Ionic crystals are composed of separate positive and negative ions (Fig. 2.9). The overall dissolution process of an ionic crystal MA (M, A, A ) can be represented by the reaction... 

The scope of kinetics includes (i) the rates and mechanisms of homogeneous chemical reactions (reactions that occur in one single phase, such as ionic and molecular reactions in aqueous solutions, radioactive decay, many reactions in silicate melts, and cation distribution reactions in minerals), (ii) diffusion (owing to random motion of particles) and convection (both are parts of mass transport diffusion is often referred to as kinetics and convection and other motions are often referred to as dynamics), and (iii) the kinetics of phase transformations and heterogeneous reactions (including nucleation, crystal growth, crystal dissolution, and bubble growth). 

MOLECULAR ASPECTS ON THE DISSOLUTION AND NUCLEATION OF IONIC CRYSTALS IN WATER... 

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