Abstract: In this article, the synthesis and characterisation of pure tephroite are discussed. At room temperature, the synthesized pure tephroise be decomposed completely by dilute hydrochloric acid,salphuric acid or phosphoric acid. It is found by calorimetry that the reaction of tephroite with hydrochloric acid releases the heat to be 160.1±3.5 kJ per mole. The determined value of heat of reaction is close to the calculated value of △H°₂₉₈ based on deta from literature.
From the deterarined value of the heat of reaction, the laitice enargy of Mn₂SiO₄ is calculated to be -8045 kJ·mol^-1, the enthalpy of hydration of SiO₄^4- (g) is -4439.3 kJ.mol^-1.