Sulfur, Elemental

CAS RN:7704-34-9

Other Properties

Atomic Number 16; Valences 2, 4, 6
Ignites in air above 261 deg C, in oxygen below 260 deg C, burning to the dioxide; combines readily with hydrogen; combines in the cold with fluorine, chlorine, and bromine; combines with carbon at high temperatures; reacts with silicon, phosphorus, arsenic, antimony and bismuth at their melting points; combines with nearly all metals; with lithium, sodium, potassium, copper, mercury and silver in the cold on contact with the solid; with magnesium, zinc and cadmium very slightly in the cold, more readily on heating; with other metals at high temperatures. Does not react with iodine, nitrogen, tellurium, gold, platinum and iridium.
Amber-colored crystals. The stable at ordinary temperature, density: 2.06; when heated to 94.5 deg C becomes opaque owing to formation of monoclinic sulfur /alpha-Sulfur/
Opaque, light- yellow, brittle, needle-like crystals; stable between 94.5 oto 120 deg C. Passes slowly into the rhombic form on standing; density 1.96; mp 115.21 deg C /beta-Sulfur/
MP: 106.8 deg C /gamma-Sulfur/
Mol wt approx 200,000; insoluble in solvents used for orthorhombic form; amorphous form; metastable, gradually reverts to alpha-form /Polymeric sulfur/
Sublimed and washed sulfur are in form of fine, yellow crystalline powder /Sulfur, pharmaceutical/
Liquid-water interfacial tension: (est) 50 dynes/cm = 0.05 N/m at 127 deg C; ratio of specific heats of vapor (gas): 1.582 (est)
Heat of Fusion: rhombic (alpha): 62.25 J/g at 112.6 deg C; monoclinic (beta): 43.54 J/g at 119.0 deg C
Occurs in ... various molecular aggregations /allotropes/ which differ in solubility, specific gravity, crystalline form, etc. ... Sulfur also exhibits dynamic allotropy, ie, the various allotropes exist together in equilibrium in definite proportions, depending on the temperature and pressure. Sulfur crystalizes in at least two distinct systems: the rhombic and monoclinic forms. Rhombic sulfur is stable at atmospheric pressures up to 95.5 deg C ... Monoclinic sulfur is then stable up to its natural melting point of 114.5 deg C
When the liquid phase consists solely of octatomic sulfur rings, the temperature ranges at which the various modifications form are called the ideal freezing points. The temperature at which the crystalline forms are in equilibrium with liquid sulfur containing equilibrium amounts of S(pie) and S(mu) are called natural freezing points
At room temp the thermodynamic stable sulfur modification is orthorhombic sulfur that converts at 94 deg C to monoclinic sulfur. The latter melts at 124-128 deg C forming a mixture of liquid allotropes that includes cyclooctasulfur, cyclododecasulfur, as well as chain species.
Sol in light petroleum and turpentine oil, and in hot aq soln of alkali hydroxides forming polysulfides and thiosulfates; Solubility: 1 in 60 chloroform, 1 in 600 ether /Precipitated sulfur/
Very slightly sol in water and alc; incompletely soluble in carbon disulfide; soluble in chloroform, ether, light petroleum, toluene, and fixed and volatile oils /Sublimed sulfur/
Liquid heat capacity = 0.230 BTU/lb deg F at 260 deg F
Ideal gas heat capacity = 0.021 BTU/lb deg F at 90 deg F
Four naturally occurring isotopes: 32 (95.0%); 33 (0.76%); 34 (4.22%); 36 (0.014%); artificial, radioactive isotopes: 29-31; 35; 37; 38
Research tool in studying mechanism of rubber vulcanization and polymerization of synthetic rubber, role of sulfur in the coking process and in steel, effect of sulfur on engine wear, sulfur removal in the viscose process, behaviour of detergents during ashing, sulfur deposition in diesel engines, action of sulfur in silver plating solutions, protein metabolism, surface active agents and surface phenomena, drug actions, etc. /Sulfur-35/
Sulfur Decay Pathways
Natural Isotopes

Isotope Relative % Abundance Half-life
Sulfur-32 95.02 Stable
Sulfur-33 0.75 Stable
Sulfur-34 4.21 Stable
Sulfur-36 0.02 Stable
Sulfur Decay Pathways
Artificial Isotopes

Isotope Half-life Mode of Decay Decay Energy (MeV)
Sulfur-26 Unknown
Sulfur-27 Unknown electron capture to P-27 18.260
Sulfur-28 125 milli seconds electron capture to P-28; electron capture + proton to Si-27 11.230; 9.170
Sulfur-29 197 milli seconds electron capture to P-29 13.790
Sulfur-30 1.178 seconds electron capture to P-30 6.138
Sulfur-31 2.572 seconds electron capture to P-31 5.396
Sulfur-35 87.51 days beta to Cl-35 0.167
Sulfur-37 5.05 minutes beta to Cl-37 4.865
Sulfur-38 170.3 minutes beta to Cl-38 2.937
Sulfur-39 11.5 seconds beta to CL-39 6.640
Sulfur-40 8.8 seconds beta to CL-40 4.710
Sulfur-41 2.6 seconds beta to Cl-41 0.880
Sulfur-42 0.56 seconds beta to Cl-42; beta + neutron to Cl-41 7.770; 2.000
Sulfur-43 220 milli seconds beta to Cl-43; beta + neutron to CL-42 11.500; 4.400
Sulfur-44 123 milli seconds beta to CL-44; beta + neutron to CL43 9.100; 5.100
Sulfur-45 82 milli seconds beta to Cl-45; beta + neutron to CL-44 14.100; 7.100
Sulfur-46 >200 nano seconds
Sulfur-47 >200 nano seconds
Sulfur-48 >200 nano seconds
Sulfur-49 <200 nano seconds neutron emission to S-48 0.300
Find more information on this substance at: Hazardous Substances Data Bank , TOXNET , PubMed