Mercury sulfide Mercury sulfide Mercury sulfide, mercuric sulfide, mercury sulphide, or mercury(II) sulfide is a chemical compound composed of the chemical elements mercury and sulfur. It is represented by the chemical formula HgS. It is virtually insoluble in water. HgS is dimorphic with two crystal forms: Crystals of red, α-HgS, are optically active. This is caused by the Hg-S helices in the structure. β-HgS is precipitated as a black powder when HS is bubbled through solutions of Hg(II) salts. β-HgS is unreactive to all but concentrated acids. Mercury metal is produced from the cinnabar ore by roasting in air and condensing the
Ore extension which means that "δ" is a homomorphism of abelian groups satisfying Then the Ore extension "R"["x";"σ","δ"], also called a skew polynomial ring, is the noncommutative ring obtained by giving the ring of polynomials "R"["x"] a new multiplication, subject to the identity If "δ" = 0 (i.e., is the zero map) then the Ore extension is denoted "R"["x"; "σ"]. If "σ" = 1 (i.e., the identity map) then the Ore extension is denoted "R"["x","δ"] and is called a differential polynomial ring. The Weyl algebras are Ore extensions, with "R" any commutative polynomial ring, "σ" the identity ring endomorphism, and "δ" the