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Microfluidic screening of potassium nitrate polymorphism

P. Laval, C. Giroux, J. Leng, J.-B. Salmon — J. Crystal Growth 310 (2008) 3121

publié le , mis à jour le

We developed a microfluidic device for the investigation of crystallization kinetics from solution.
The device allows to store hundreds of about 100 nL droplets containing a given solute and to
control their temperature within 0.1°C. Upon cooling, we observe independent and mononuclear crystallization events ;
crystal dissolution occurs as the temperature is raised. For potassium nitrate (KNO3) in water,
these thermal cycles reveal the existence of two concomitant polymorphic forms.
We measure the solubility curves of each structure for the first time and define unambiguously the metastability extent of the solution.
We describe why these results essentially stem from the miniaturized scale of the crystallization reactors.