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also sul·phur  (sŭl′fər)
1. Symbol S A pale yellow nonmetallic element occurring widely in nature in several free, allotropic and crystal forms and combined in numerous sulfates and sulfides. It is used in black gunpowder, rubber vulcanization, the manufacture of insecticides and pharmaceuticals, and in the preparation of sulfur compounds such as hydrogen sulfide and sulfuric acid. Atomic number 16; atomic weight 32.066; melting point 115.21°C; boiling point 444.61°C; specific gravity at 20°C (rhombic) 2.07, (monoclinic) 2.00; valence 2, 4, 6. See Periodic Table.
2. Any of various butterflies of the subfamily Coliadinae of the family Pieridae, having yellow or orange wings often marked with black.
tr.v. sul·fured, sul·fur·ing, sul·furs also sul·phured or sul·phur·ing or sul·phurs
To treat with sulfur or a compound of sulfur.

[Middle English, from Anglo-Norman sulfre, from Latin sulfur.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.