Sodium Ethyl Xanthate (Molecule of the Month for March 2007)
Xanthates are water-soluble chemicals that are used primarily in the mining industry. Xanthates can be obtained by reacting an alcohol with carbon disulphide and an alkali such as sodium hydroxide or potassium hydroxide. The alcohols employed are not unique. They can form ethyl, butyl (isobutyl, normal butyl, secondary butyl), propyl (isopropyl, normal propyl) and amyl (isoamyl, normal amyl, secondary amyl) xanthates, in dry forms, such as powder, granules, pellets, tablets or flakes. Xanthate is the common name for chemical reagents used in the flotation of base and precious metals, which is the standard method for separating valuable minerals, such as gold, copper, lead or zinc minerals, from non-valuable minerals, such as limestone or quartz (gangue).
To extract values, conditioned ores are mixed in a solution of water and xanthates and then agitated in flotation cells. Xanthates may be added in liquid or solid form. The xanthates cause the minerals to attach themselves to air bubbles and then float to the top of the flotation cell. As values reach the surface, the bubbles form a froth that overflows into a trough for collection. The residual may be re-used for additional recovery or removed for disposal. Most of the xanthate is consumed in the process. Several flotation processes are required for different ores. Since each ore is unique, there is no standard flotation procedure and no standard grade or type of xanthate used to extract specific values. Each producer has its own grades for xanthate composition, including purity, which is stated as a minimum percentage up to 100 per cent, and moisture. Four types of xanthates (ethyl, butyl, propyl and amyl) are produced in various combinations with sodium and potassium, which are stabilizers in the chemical formula.
The key reagent is carbon disulphide. A special plant must be built for its production, in other words, a xanthate manufacturer must have two plants, one for carbon disulphide and other for xanthate production. So the production cost is influenced by carbon disulphide. Carbon disulphide (CS2) is also known as carbon bisulphide and sometimes dithiocarbonic anhydride. It is a faintly yellow highly flammable liquid with a strong disagreeable odour. Carbon disulphide is manufactured from hydrocarbons and sulfur and is a very flammable liquid which is therefore extremely hazardous to manufacture and transport.
Formal Chemical Name (IUPAC)
sodium O-ethyl carbonodithioate
Update by Karl Harrison
(Molecule of the Month for March 2007 )
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