An Investigation of the Constitution of the Mercury-Tin System1

An investigation of the constitution of the mercury-tin system was made by a combination of three techniques: differential thermal analysis; diffusion and chemical analysis; and X-ray diffraction. The mercury-silver-tin system is of interest because it is the basis of dental amalgam, the most important single dental restorative material. Information as to the constitution of these alloys is incomplete for both the ternary system and the mercury-tin binary system. This study was devoted to the investigation of the mercury-tin system as a prerequisite to a study of the ternary alloys. The results obtained by the various methods are not in complete agreement. They indicate that the system is more complex than previously reported. Additional evidence for the beta phase as reported by Prytherich was found but the composition limits and eutectoid temperature remain to be confirmed. The gamma phase composition limits were found to differ from earlier values. Corroborative data for Gayler’s delta phase and possible evidence for a previously unreported epsilon phase have been found by X-ray diffraction. The thermal analysis results indicate the possible existence of additional phases unconfirmed by other methods. A modified mercury-tin phase diagram based upon these findings is proposed.