| dc.description.abstract | Synthetic, biological and mineralogical carbonate-containing
apatites have been studied, principally by infra-red
absorption spectroscopy (using polarised or unpolarised radiation),
The substitution of a carbonate ion for two hydroxyl ions in
the apatite lattice has been confirmed, by chemical analyses, and
the variation of the lattice constants with the degree of substitution
determined. The orientation of the carbonate ion has been
determined by using polarised infra-red radiation; its plane is
approximately parallel with the c-axis.
The carbonate ions in dental enamel are in two different
environments; the lane of the carbonate ion in these two environments
is nearly parallel and perpendicular to the c-axis. One of
these environments is very probably the substitution for hydroxyl
ions discussed above; this accounts for only a small fraction of
the carbonate ions, the remainder are probably adsorbed on the
surface of the apatite crystals.
A number of carbonate-containing apatites prepared in
aqueous systems have been studied. These show similarities to
enamel but with the carbonate ions in different relative proportions in the two different environments present in enamel.
Some apatites have been prepared which have absorption
bands due to molecular carbon dioxide. This has been confirmed
by preparing apatites containing the heavy isotope of carbon, carbon-13.
The orientation of the carbonate ion in francolite has been
determined and is consistent with it occupying the sloping face
(with respect to the basal plane) of the space left by a phosphate
ion. The environment of the carbonate ion in francolite is
different from that in enamel,
The hydroxyl ion in enamel and francolite is oriented 'with
the 0-H bond parallel with the c-axis of the apatite lattice.
The assignment of the hydroxyl band in the infra-red spectrum of
enamel has been confirmed by deuteration experiments. | en_US |
