The disodium salt was prepared by neutralizing the diphosphonic acid (130 mg, mmol) with NaHCO 3 ( mg, mmol) in H 2 O (5 mL) for 1 hour at room temperature then concentrating to 3 mL under reduced pressure. EtOH (3 mL) was added and the mixture cooled. After centrifugation, solvent was pipetted off and the residue solid triturated three times with absolute EtOH. Drying under high vacuum afforded the disodium salt (52 mg). An additional 60 mg of sodium salt could be recovered from the filtrate by concentration and trituration with absolute EtOH.