TY - JOUR

T1 - Theory of electrolyte crystallization in magnetic field

AU - Madsen, Hans Erik Lundager

PY - 2007

Y1 - 2007

N2 - Crystallization from aqueous solution of a sparingly soluble electrolyte is accelerated by magnetic field if the crystalizing phase is a diamagnetic salt of a weak acid, and crystallization is from neutral or acid solution in ordinary (not heavy) water. Since the effect of Lorentz force is negligible, if not absent, the key property is likely to be the spin of protons which, by virtue of their half-integral spin, are fermions. An effect on crystal growth kinetics has been demonstrated, and the apparent effect on nucleation concerns the growth rate of nuclei. We are thus dealing with surface phenomena. The basis of the theory is a crystal model of a sparingly soluble salt with NaCl structure, where the ions are divalent, and the anion is a base. It is assumed that almost all the anions in the surface layer are protonized, and that an approaching metal ion pushes the proton away to a neighbouring anion, which then becomes doubly protonized. If the two protons are in the same spin state, the Pauli principle requires that one of them enter a state of higher energy, which enhances the activation energy and reduces the rate of the process, but even with opposite spins the incoming proton must enter an excited state due to its momentum. Spin relaxation in magnetic field may remove hindrances to proton transfer. The theory is supported by numerical results from model calculations.

AB - Crystallization from aqueous solution of a sparingly soluble electrolyte is accelerated by magnetic field if the crystalizing phase is a diamagnetic salt of a weak acid, and crystallization is from neutral or acid solution in ordinary (not heavy) water. Since the effect of Lorentz force is negligible, if not absent, the key property is likely to be the spin of protons which, by virtue of their half-integral spin, are fermions. An effect on crystal growth kinetics has been demonstrated, and the apparent effect on nucleation concerns the growth rate of nuclei. We are thus dealing with surface phenomena. The basis of the theory is a crystal model of a sparingly soluble salt with NaCl structure, where the ions are divalent, and the anion is a base. It is assumed that almost all the anions in the surface layer are protonized, and that an approaching metal ion pushes the proton away to a neighbouring anion, which then becomes doubly protonized. If the two protons are in the same spin state, the Pauli principle requires that one of them enter a state of higher energy, which enhances the activation energy and reduces the rate of the process, but even with opposite spins the incoming proton must enter an excited state due to its momentum. Spin relaxation in magnetic field may remove hindrances to proton transfer. The theory is supported by numerical results from model calculations.

KW - Former LIFE faculty

KW - Magnetic fields

KW - Proton transfer

KW - Surface processes

KW - Salts

U2 - 10.1016/j.jcrysgro.2007.04.023

DO - 10.1016/j.jcrysgro.2007.04.023

M3 - Journal article

VL - 305

SP - 271

EP - 277

JO - Journal of Crystal Growth

JF - Journal of Crystal Growth

SN - 0022-0248

IS - 1

ER -