Ultrasonic study of epsomite (MgSO4.7H2O) under pressure

We present an ultrasonic study of the elastic moduli of epsomite (MgSO₄.7H₂O) in the temperature range 77-295 K at pressures up to 2.8 GPa. Elastic properties of epsomite MgSO₄.7D₂O at room temperature conditions (p=0-2.8 GPa) were also measured. The anomalies in dependencies of elastic characteristics were identified as phase transition points. Our research has shown that the elastic properties and the sequence of phase transitions for MgSO₄.7H₂O and MgSO₄.7D₂O are very similar at room temperature. The picture of transformations of the compressed epsomite significantly changes below 285 K.