Conference paper

The Precipitation of Calcium Phosphates in the Presence of Magnesium

George H. Nancollas ; Chemistry Department, State University of New York at Buffalo, Buffalo, New York U.S.A.
Branko Tomažič ; Chemistry Department, State University of New York at Buffalo, Buffalo, New York U.S.A.
Mason Tomson ; Chemistry Department, State University of New York at Buffalo, Buffalo, New York U.S.A.

Abstract

The kinetics of growth of calcium ·phosphate on hydroxyapatite
(HAP) seed crystals was studied at 25 °c and 37 °c and at constant
physiological pH in stable supersaturated solutions of calcium phosphate
containing various concentrations of magnesium ion. The
pH ' was maintained constant by means of the pH-stat controlled
addition of base and the growth was followed by analyzing the
solutions for calcium, phosphate and magnesium. Grown material
was characterized chemically, by subsequent dissolution kinetic
experiments, by infrared spectroscopy and by specific surface area
(SSA) measurement. Magnesium ion reduces the overall rate 'of crystallization by stabilizing the precursor formed initially in the
growth runs. Whereas the stoichiometry of the first formed surface
phase corresponds to that of octacalcium phosphate (OCP) in the
absence of magnesium, lower molar Ca/P ratios, possibly a mixture
of dicalcium phosphate dihidrate (DCPD) and OCP are indicated in
its presence. The inhibitory effect of magnesium on crystal growth
of HAP and DCPD and some other inorganic compounds is described
and discussed in terms of adsorption of magnesium ion at
active growth sites and stabilization of growth precursor phases.

Keywords

Hrčak ID:

196436

URI

https://hrcak.srce.hr/196436

Publication date:

22.12.1976.

Visits: 1.116 *