7.7 Nature of Kinetic Anomalies and Crystal Growth Mechanisms 285
inherits the structural changes of the bulk (Punin and Petrov 1972; Chernov and
Sipyagin 1980; Glikin et al. 1982; Bocharov and Glikin 2008).
The first point of view is based upon structural NMR investigations of film lay-
ers of KClO
3
saturated aqueous solutions on crystal faces of this substance
(Sipyagin et al. 1976; Chernov and Sipyagin 1980). The measurements showed that
proton mobility in the layers has abnormal values at the temperatures, at which the
growth rate anomalies occur. An additional direct proof of molecular structuring of
the adsorption layers is anisotropy of the proton mobility in directions, which are
parallel to the surface of the crystals that also confirms the proposed structural-
chemical model.
The second point of view is supported by coincidence of temperatures at which
the anomalies occur and changes in some characteristic bulk properties of the solu-
tions, e.g., solubility, partial molal heat of dissolving, partial molar volume (Punin
and Petrov 1972), and viscosity (Franke and Punin 1972), as well as by reported
abnormal solubility behavior of several salts in water (Kiryanova 2003). These
display a connection between the kinetic anomalies and solution bulk structure.
The behavior of kinetic anomaly peaks shows a simultaneous relation of adsorp-
tion layer and bulk properties to the anomalies (Glikin et al. 1982). Temperature
dependence of peak heights and positions upon supersaturation was analyzed for 32
anomalies belonged to three substances and the following values were found: for
KCl in combined regime at natural convection, anomalies of the {100} faces were
observed at 7, 12, 16, 22, and 60°C (Punin and Petrov 1972); for NaClO
3
in com-
bined regime anomalies of the {100} faces – at 36 and 39.5°C (Glikin’s data of
1974); for NaClO
3
in kinetic regime with intensive stirring (Sipyagin’s data of
1967): for {100} – at 7, 23, 36, 39.5, and 40.5°C, for {110} – at 8, 36.5, and 39.5°C,
for {111} – at 7, 36, 39.5, and 40.5°C; and for KClO
3
in kinetic regime with inten-
sive stirring (Sipyagin’s data of 1967) for {110} – at 34, 36, and 40.5°C, for {011}
– at 30 and 36°C, for {100} – at 17, 34, 37, and 44°C, for {101} – at 32, 36, and
42°C. Without going into details, the following is worth being noticed. First, dis-
crepancy in correlation between the peak height and supersaturation observed in
kinetic regime for different faces agrees with conclusion about the anomaly arising
due to structural rearrangements of the adsorption layer. Second, for various sub-
stances relation between the temperature shift of anomalies and change in super-
saturation correlates with shapes of temperature solubility curves, which also
indicate rearrangement proceeding in the bulk of the solution. Therefore, an inves-
tigation of growth-rate anomalies supports the idea about structuring the adsorption
film, which determines the growth kinetics, although anomalies themselves are
likely to be of dual nature.
It appears that revealing the nature of anomalies can acquire a key significance in
understanding the structure of the adsorption layer, which determines numerous
phenomena that are functionally related to the crystal growth rate, including faceting
and surface relief, inclusions, capturing isomorphic and other impurities, epitaxy,
etc., and will ultimately provide the basis for a crystal-genetic theory of solutions.
However this approach requires a totally new methodological basis. Usual direct
measurements of crystal growth rates in the course of conventional precipitation