Thermodynamics of Ionic Solid Solutions and Its Application to the Formation and Stability of Biominerals

Abstract

AbstractThe classification of equilibrium between ionic solid solutions and aqueous solutions by Roozeboom is interpreted as being a result of the ideal or regular behaviour of the ionic solid solutions. Due to the fact that the solubility products of isomorphous compounds which form ionic solid solutions differs in general by several orders of magnitude, it is very unlikely that precipitates differ much from the stoichiometry of one of these compounds. This principle is applied to the problem of biominerals, especially bone mineral. As a result it appears that the first mineral deposited in bone is octocalcium phosphate. Under in vivo conditions this phase is transformed into a mixture of three other calcium phosphates having a much lower solubility. The solubility controlling phase in living bone appears to be octocalcium phosphate which is continuously formed during the turn‐over of bone. This model for bone mineral has lead to the explanation of the formation of renal stones, pathological calcifications and osteoporosis as a consequence of slight chronic magnesium deficiency. The action of magnesium is mediated by the osteocytes.