BETA-CYCLODEXTRIN HYDRATION - A CALORIMETRIC AND GRAVIMETRIC STUDY

The standard heat of solvation of beta-cyclodextrin (beta CD) with one mole of water is determined as -10.50 kJ per mol beta CD, after measu rement of the heat of dissolution of beta CD samples containing variou s amounts of water. This value is constant in the composition range be ta CD.nH(2)O, with 0 < n < 11 (n is the number of water molecules atta ched). The thermogravimetric study of the kinetics of water absorption by beta CD does not show a definite hydrate. The water content of the hydrate is controlled by the vapour pressure and temperature alone. U nder ambient conditions, the number of water molecules bound to one be ta CD molecule lies between 10 and 12.