A calcium-sodium polysulfide chemical reagent and methods for producing the reagent. The reagent is a blend of calcium polysulfide and sodium polysulfide that can be prepared using various types, sources and ratios of lime, elemental sulfur and sulfide ion using either virgin or waste materials. The reagent is amenable to inexpensive and high rate production methods at ambient or warmer temperatures. The reagent can be used to precipitate metals from wastewater, stabilize hexavalent chrome in hazardous waste residues, remove mercury from coal fired power plants, and as an electrolyte in large-scale bromide/polysulfide electrical storage batteries.