P 2221 (OTTO) Potassium ethylxanthate Cas 140-89-6 - used in the mining industry as flotation agent for extraction of the ores of copper, nickel, and silver.The method exploits the affinity of these "soft" metals for the organosulfur ligand. P 2221 (OTTO) Potassium ethylxanthate Cas 140-89-6 - used in the mining industry for the separation of ores.