Abstract
The DSC dehydration scans of raffinose pentahydrate (R5W) reveal three symmetrical endotherms of which only two depend on the heating rate. Enthalpies corresponding to each of the two lower endotherms corresponded to 20% of the total enthalpy change. They were therefore assigned to R4W and R3W, respectively. XRD-DSC measurement shows the thermodynamic and structural changes occurring during a complete dehydration of R5W. On the removal of the first water molecule, to yield a R4W stoichiometry small peaks appear at ca. 8°(2θ), which do not appear in the R5W diffractogram. In order to obtain some additional information about possible existence of intermediate hydrates, a simulation was performed on the effects of removing each one of the five water molecules in turn from their different locations in R5W. From these results the R4W crystal structure was estimated.
