Water Vapor Pressure Dependence of Crystallization Kinetics of Amorphous Forsterite

2018 ◽  
Vol 2 (8) ◽  
pp. 778-786 ◽  
Author(s):  
Daiki Yamamoto ◽  
Shogo Tachibana
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Crystallization Kinetics ◽  
Pressure Dependence ◽  
Water Vapor Pressure ◽  
Kinetics Of

Quantitation of crystallinity in substantially amorphous pharmaceuticals and study of crystallization kinetics by X-ray powder diffractometry

2000 ◽  
Vol 15 (1) ◽  
pp. 2-6 ◽  
Author(s):  
Rahul Surana ◽  
Raj Suryanarayanan
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Crystallization Kinetics ◽  
Water Vapor Pressure ◽  
Three Dimensional ◽  
Weight Percent ◽  
X Ray ◽  
Amorphous Pharmaceuticals ◽  
Integrated Intensities ◽  
Kinetics Of

The first object was to develop an X-ray diffractometric method for the detection and quantification of crystalline sucrose when it occurs as a mixture with amorphous sucrose. Standards consisting of amorphous sucrose physically mixed with 1 to 5 weight percent crystalline sucrose were prepared. The sum of the background subtracted integrated intensities of the 12.7°2θ (6.94 Å) and 13.1°2θ (6.73 Å) sucrose diffraction peaks were linearly related to the weight percent crystalline sucrose. The limits of detection and quantitation of crystalline sucrose were 0.9% and 1.8% w/w, respectively. The second object was to study the kinetics of crystallization of sucrose as a function of temperature (at 102, 105 and 110 °C under a water vapor pressure of 0 Torr) and water vapor pressure (17.4, 19.8 and 21.4 Torr at 27 °C). In all cases, the crystallization kinetics was best described by the Avrami-Erofe’ev model (three-dimensional nucleation).

THE EFFECT OF WATER VAPOR UPON THE DEHYDRATION OF CaSO4•2H2O

1964 ◽  
Vol 42 (4) ◽  
pp. 792-801 ◽  
Author(s):  
H. G. McAdie
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Water Vapor Pressure ◽  
Vapor Pressures ◽  
Heat Of Solution ◽  
Temperature Dependent ◽  
Exponential Factor ◽  
Fixed Composition ◽  
Kinetics Of ◽  
Partial Water

Kinetics of the two-stage dehydration of CaSO4•2H2O have been examined under controlled water vapor pressures up to one atmosphere. For both stages water vapor initially accelerated the rate of dehydration and subsequently retarded it. Separate, temperature-dependent water vapor pressures were noted above which each stage could be suppressed.The hemihydrate was clearly defined either as a change in the rate of weight loss during dehydration or, at higher water vapor pressures, as a fixed composition. The heat of solution of the hemihydrate increased linearly with the partial water vapor pressure present during its formation, but was independent of the formation temperature over the range studied. Activation energy and pre-exponential factor for the dihydrate → hemihydrate process also increased linearly with water vapor pressure. Hemihydrates produced at the extremes of water vapor pressure corresponded to the α- and β-modifications, as defined thermodynamically, and the production of a hemihydrate series with properties varying linearly from one extreme to the other is discussed.

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