Comparison of (34) with the experiment data, see fig. 16, made it possible to
determine the parameters values by
means of least squares method,
а
8
= 5.89·10
-4
с
-1
;
Х
8∞
= 8.41·10
-4
M/dm3, (35)
X
8∞
– calcium ions concentration
when crystallization rate by (34) is equal
to zero. This value may be formally
identified
with
boundary
X
8
concentration established in CHCS
metastable state. Taking into account the
form of (34) dependence we come to the
conclusion that starting from i = 90 for
our conditions the crystallization is
controlled by diffusion. Till this moment
the processes of crystallization and initial crystal nuclei growth were the most
decisive.
Indeed, we can see from Fig. 16, that dependence (32) has three special points at
i = 68; 80; and 90 [1,12]. The point i = 90 corresponds to the crystallization start
controlled by diffusion, point i = 68 corresponds to free Ca
2+
ions maximum
concentration, within 68 < i < 80 total nucleation takes place, and at 80 < i < 90 there
is the initial phase of crystal nuclei growth, see Fig. 15, where the start of curve CaCO
3
concentration is shown.
Figure 16. Dependence of (29) curve 1 and (30)
line 2, upon the number of measurement.
Numbers 68,80 and 90 indicate the measurements
num-bers, 10.03–value of (29) function at point i
= 90.
90
10.03
1
2
1
Figure 17. Experimental dependence of Ca
2+
concentration change rate upon measurement:
curve 1 and approximation (31), thick curve 2.
1
1
2
90
5.00·10
-5
Figure18. Dependence of Ca
2+
concentration
upon the number of measurement i - curve 1
and approximation (31) curve 2. At section i >
90 both curves coincide.
1
2
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