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Chapter II Solution Growth….
observed that crystals of non-polar organic compounds grow from non- polar
organic solvents at rates comparable to the solidification of melts, suggesting
that the main difference between two processes is the interaction of solute
and solvent molecule. Many additives that influence crystal growth
morphology [44] and the crystal growth rates [45] are studied. Many times a
change in the growing crystalline habit is desirable. A habit of growing crystal
can be altered by changing the temperature of growth, changing the pH of
solution, adding a habit modifying agent and changing the solvent.
Moreover, to have a regular and even growth, the level of super-
saturation has to be maintained equally around the surface of the growing
crystal. An uneven growth leads to localized stresses at the surface
generating imperfection in the bulk crystal. The concentration gradients that
exist in the growth vessel at different faces of crystal cause fluctuations in
super-saturation, which seriously affects the growth rate of individual faces.
The gradient at the bottom of the growth vessel exceeds the meta-stable zone
width, resulting into spurious nucleation. However, the degree of formation of
concentration gradients around the crystal depends on the efficiency of
agitation of the solution. For these reasons, the agitation of saturated solution
in either direction at an optimized speed of stirrer motor is advisable.
2.7 Selection of Seeds
Gilman [8] compared the artificial growth of crystals with agriculture.
Alike in agriculture, good crystal growth needs good quality seeds,
uninterrupted supply of nutrients and allowing the fittest to grow. Getting a
proper quality of seed crystals is a prime factor in crystal growth. The classical
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