MP and MS, are shown in Fig. 1. In all three cases, the melting profile is similar to the profile during cooling. The crystallization behavior of MP was already described (Verstringe et al., 2013). In this previous study, it was concluded that MP first crystallized into an α polymorphic form which transformed into a sub-α polymorph upon further cooling. This transformation occurs via the solid state and is reversible, as can be seen in the melting profile. Sub-α forms do not have a melting point. However, the enthalpy change associated with the transition can be measured by DSC and yields a ‘melting point’ (i.e. the peak temperature) (Hagemann, 1988; Krog, 2001). Similar to MP and in accordance with the study of Vereecken et al. (2009), MS