Sulfur parameters

Physical properties: Sulfur is a yellow crystal that exists as a gas, liquid, or solid at different temperatures. The molecular formulas are S2, S6, and S8 respectively, with molecular weights of 64, 192, and 256 respectively. Melting point: 112°C–120°C, auto-ignition temperature: 232°C, ignition temperature: 250°C, boiling point: 444.6°C, density: 1.96 g/ml–2.07 g/ml, flash point: 20.7°C, explosion limit (lower limit): 35.0% (by volume). When sulfur is heated, the following changes occur: Solid (S8) at 94.5°C; monoclinic crystal structure at 112.8°C; S8 becomes fluid and liquefies at 160°C, forming a brown liquid; at 190°C it turns into a dark brown viscous substance (S8); at 444.5°C it becomes a yellow gas (S6); and at 1000°C it turns into a colorless gas (S2). Solid sulfur is usually in the form of S8, with a saddle-shaped structure, as shown in the diagram. When sulfur is heated, its molecular structure changes; at 160°C, the S8 structure begins to break down into open chains, resulting in an increase in viscosity. The viscosity reaches its maximum at 190°C, at which point the liquid sulfur is brownish-red and highly fluid. Above 190°C, the average length of the chains decreases, and the viscosity drops again. Liquid sulfur has its best flow properties between 130°C and 160°C, with a viscosity of 7 cp at 143°C and 9000 cp at 183°C. Therefore, the temperature at which liquid sulfur is transported should be maintained between 130°C and 160°C. Based on this characteristic, steam at 0.3 MPa (142.9°C) is used for heating and insulation in such systems. The vapor pressure of sulfur at different temperatures is shown in Table 2. Table 2 Sulfur vapor pressure Temperature (°C) Vapor pressure (mmHg) Temperature (°C) Vapor pressure (mmHg) 49.7 0.00034 242 8.4 78 0.002 245 10.0 104 0.01 265 20.0 131.9 0.081 306.5 53.5 135 0.10 342 106 141 0.13 363 176 157 0.33 374 240 172 0.63 393 436 181 1.0 410 443 190 1.4 427 580 221.3 3.14 444.6 760 At temperatures close to 760°C, sulfur vapor is almost entirely in the form of S2. Chemical properties: It burns in air to produce SO2; S + O2. When burned, SO2 reacts with hydrogen to form H2S; S + H2. At 300°C, H2S is formed