Sulfur:
Sulfur. Brimstones; sulphur. S; at. Wt. 32.064 0.003; at. No. 16; valences 2, 4, 6. four naturally occuring isotopes: 32 (95.0%); 33 (0.76%); 34 (4.22%); 36 (0.014%); artificial, radioactive isotopes: 29-31; 35; 37; 38. Has been koown from very early times. Occurs both in the tree state and in combination, mainly as sulfides and sulfates; constitutes 0.05% of the crust of the earth. Industrial prepn by Frasch process: Faith, Keyes & Clark's Industrial Chemicals, F. A. Lowenheim, M. K. Moran, Eds. (Wiley-Interscience, New York, 4th ed., 1975) pp 786-794. Exists in several allotropic modifications; at S.T.P. Only the orthorhombic, cyclooctasulfur (Sa) is thermodynamically stable: Meyer, Chem. Rev. 64, 429 (1964). Prepn of cyclohexasulfur: Bartlett et al., J. Am. Chem. Soc. 83, 10 (1961); of cyclohepta- and cyclodecasulfur: Schmidt et al., Angew. Chem. Int. Ed. 7, 632 (1968); of cyclononasulfur- Schmidt, Wilhelm, Chem. Commun. 1970, 1111; of cyclododecasulfur- eidem, Angew. Chem. Int. Ed. 5, 964 (1966). Review of structures of elemental sulfur: Meyer in Advan. Inorg. Chem. Radiochem. 18, 287-317 (1976). Reviews of sulfur and its compds: W. N. Tuller, The Sulphur Data Book (McGraw-Hill, New York, 1954); B. Meyer, Elemental Sulfur (Interscience-Wiley, 1965); Inorganic Sulphur Chemistry, G. Nickless, Ed. (Elsevier, New York, 1968); Schmidt, Siebert, in Comprehensive Inorganic Chemistry vol. 2, J. C. Bailar, Jr. et al., Eds. (Pergamon, Oxford, 1973) pp 795-933.

Orthorhombic, cycloocta- or a-sulfur, amber-colored crystals; the stable form at ordinary temperature. d 2.06; when heated to 94.5, becomes opaque owing to the formation of monoclinic sulfur.

Monoclinic, cycloocta or b-sulfur. light-yellow, opaque, brittle, needle-like crystals; stable between 94.5-120. Passes slowly into the rhombic form on standing. d 1.96; mp 115.21: West, J. Am. Chem. Soc. 81, 29 (1959). bp about 444.6. A second monoclinic form, g-sulfur or mother-of-pearl sulfur is also known; mp 106.8.

Sulfur is insol in water; sparingly sol in alcohol, in ether; sol in carbon disulfide (one gram/2 ml); sol in benzene (about 2.4% at 30', much more at higher temps.), in toluene. Liquid ammonia (anhydr) dissolves 38.5% S at -78; acetone dissolves 2.65% at 25; methylene iodide dissolves 9.1% at 10; chloroform dissolves about 1.5% at 18. For other solvents see Tuller, op. cit. Ignites in air above 261, in oxygen below 260, 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.

Polymeric sulfur, Crystex. Amorphous form; mol wt approx 200,000. Metastable, gradually reverts to the a-form. Insol in solvents used for orthorhombic form. Reviews: Meyer, loc. cit. (1964); A. V. Tobolsky, W. J. MacKnight, Polymeric Sulfur and Related Polymers (Interscience, New York, 1965) pp 87-97.

Note: See also Sulfur, Pharmaceutical.

USE: In mfg sulfuric acid, carbon disulfide, sulfites, insecticides, plastics, enamels, metal-glass cements; in vulcanizing rubber; in syntheses of dyes; in making gunpowder, matches; for bleaching wood pulp, straw, wool, silk, felt, linen. Caution: May cause irritation of skin, mucous membranes.
Ref.: 8948, pp 1416-1417.
The Merck Index - Eleventh Edition.
Copyright 1989 by Merck & Co., Inc.