There are three triple point :
- 1 (95.4 c 1×10-4 latm) - rhombic s is in equilibrium with monoclinic s, and have the same vapor pressure.
-2 (119 c 5×10-4 latm) - monoclinic s melt ; this is the triple point for Sm-Sl-Sg.
-3 (151 c , 1288 atm) - rhombic, monoclinic , and liquid s are at equilibrium.
The critical point - where liquid and gaseous s have the same density - is off to the right at 1041 c and 203.3 atm