Abstract
Potassium nitrate exists in several crystalline forms depending upon both the temperature and the pressure (1,2). The three easily observed forms are the orthorhombic KNO3II, stable under standard conditions, a trigonal form, KNOoI, staole above 127.7°C at atmospheric pressure (3), and a second trigonal form, KNO3III, which is typically formed when KNO3I is cooled. The persistence of this form varies with, among other things, its degree of confinement; that is, the expansion of the crystallites transforming from I?III may be unrestrained in a shallow pan, but in a sample cup or well the points of contact are under pressure, so a confined sample transforms more quickly to the orthorhombic phase (4).
Keywords
Orthorhombic Phase Heating Peak Trigonal Form Unidirectional Compression Single Crystal Potassium NitratePreview
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