Analytical comparison between unprepared and calcined magnetitum (Cishi)

Abstract

The phases, chemical composition, surface appearance, crystal size, specific surface and thermal behavior of the unprepared and calcined forms of the mineral Magnetitum (Cishi), used as Chinese traditional medicine, were characterized by using X-ray powder diffraction, scan electron microscopy, inductively coupled plasma-atomic emission spectometry (ICP) and thermogravimetric (TG). The results indicated that after calcination the main phase Fe₃O₄ of the calcined Magnetitum (Duan Cishi) remained, while the Fe₂O₃ phase disappeared. The contents of the harmful chemical elements Cd and Pb were obviously reduced, while the crystal size increased from 24.5 to 35.7 nm and surface loosened. There were different TG curves for unprepared and calcined Magnetitum (Cishi) samples on heating. The former showed two weight-losing steps (at 367.9-422.1?C and 568.8-594.1?C), and the latter only one. These results might serve as a base for quality evaluation of Magnetitum (Cishi).