چکیده (انگلیسی):

The objective of this study was to
characterize the moisture sorption of magnesium
stearate and the morphological changes, if any,
resulting from moisture sorption. Six samples of
commercial magnesium stearate USP were examined.
Moisture sorption isotherms were obtained at 25°C and
5% to 98% relative humidity (RH) using a moisture
balance. Changes in crystal form resulting from
moisture sorption were determined by x-ray diffraction.
There were differences in the shape of the isotherm,
reversibility of moisture uptake, and shape of the
hysteresis loop in the isotherms of crystalline and
amorphous magnesium stearates. The isotherm of
crystalline magnesium stearate was almost parallel to the
pressure axis until and RH of ~ 80%.The isotherm of the
amorphous sample was characterized by continuous
uptake of water over the entire range of RH. Exposure
of amorphous magnesium stearate to RH greater than
70% resulted in the formation of the trihydrate. The
trihydrate was converted into the anhydrous form when
heated to a temperature of 100°C to 105°C. The
trihydrate could be generated by exposing the
anhydrate to RH higher than 70%.