*2.9. Stability Test*

Stability in aqueous solution was evaluated through slurry experiments. Excess of powder samples of each phase was added to 1 mL of water and stirred for 24 h in sealed vials. The solids were collected, filtered, and dried for further analysis by PXRD.

Stability at accelerated ageing conditions was also studied: 200 mg of solid was placed in watch glasses and left at 40 ◦C in 75% relative humidity using a Memmert HPP110 climate chamber (Memmert, Schwabach, Germany). The samples were subjected to the above-accelerated stability conditions for two months. PXRD was used to monitor the stability of the solid forms.
