The region of preferred nucleation of α- and β-polymorphs of L-glutamic acid from pure aqueous solution was recognized by following a swift cooling crystallization process in the temperature range of 1-40 °C in steps of every 1 °C with different stirring speeds of 24, 50, 75, 100 and 120 rpm. The prepared saturated experimental solution which was superheated to elevated temperature was subjected to swift cooling to a range of optimized experimental temperatures, with continuous stirring at different stirring speeds and the resultant supersaturation generated in the system favours the nucleation of the desired polymorphs of L-glutamic acid. The morphological distinctions of the nucleated micro crystalline polymorphs were realized by in-situ optical microscopic visualization and their structural difference was confirmed by X-ray diffraction analysis. Varying stirring speeds during swift cooling crystallization alters the regions of preferred nucleation of the 100% α-nucleations, 100% β-nucleations and α+β mixed nucleations in pure aqueous solution. It is found that the increase in the stirring speed increases the 100% α-nucleation region and decreases the α+β mixed nucleation region. The advantage of this method over the existing ones is the tuning of desired polymorphic nucleation without incorporating any nucleation inhibiting additives into the solution. Effect of stirring speed on induction period of nucleation, percentage of α- and β-nucleations, size and quality of the grown crystals were also studied. Randomly oriented cracks observed on the crystals are found to increase while increasing the stirring speed and growth period during the experiment which is mainly due to the increase in the tensile stress within the growing crystals and this very much spoils the quality of the grown crystal.

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