Abstract

The nomenclature of the xanthates and their derivatives is given. The various physical properties are covered. The recent pK_a values for ethyl xanthic acid are 2.20 or 1.43 and are in agreement with earlier reported values. The alkali metal xanthates decompose on heating or in aqueous solution. The decomposition in aqueous solution has been well studied. The thermal decomposition produces carbonyl sulfide, carbon disulfide, thiols, organic sulfides and disulfides, as well as aldehydes. The solubility of xanthate salts in water and organic solvents is given. The chemical reactions of the xanthates and their esters lead to decomposition products or new derivatives.

The methods of the manufacture of the commercial xanthates is covered. The current estimated number of xanthate plants worldwide is fifteen, and they produced 55,000 metric tons of product in 1995. Production standards are briefly discussed. Various column chromatographic methods were employed to separate the various xanthates and the separated species were detected spectroscopically at a wavelength of 305 nm.

Discussion of the health, safety, and toxicological concerns regarding the commercial xanthates showed that with proper care the xanthates and derivatives can be safely used and handled.

Although the principal use of the alkali metal xanthates and derivatives is in the mining industry, other derivatives find use in rubber compounding. Standards set by the U.S. Food and Drug Administration for the use of chemical in rubber processing and compounding (1996) included zinc butyl xanthate, ethyl and butyl dixanthogen, and a mixture of diisopropyl xanthogen disulfides. A unique use of the alkali metal xanthates is in the removal of metallic mercury from contaminated industrial land sites. The principal derivatives in use (mineral processing) are four types: dixanthogens, xanthogen formates, dialkylthionocarbamates, and the S-alkyl esters.