Q. Explain Extraction of Sulphur?

The most important method for the extraction of sulphur from native deposits is the frasc process developed by Herman frach in 1891. It consists of boring a hole from the ground  surface to the  sulphur bearing calcite deposit and lowering three  concentric pies to the ore bed superheated steam 438K is  forced down the outer pipe into the ore bed where it melts the sulphur. Compressed hot air is pumped down through the innermost pipe when a frothy mixture of molten sulphur water and air is forced to them to the surface through the middle pipe. As it comes out from the well, sulphur has a purity of 99.5-99. 9% and contains virtually no As. Se or Te.

Sulphur is also obtained as a by product in the production of coal gas and in refining crude oil and natural gas. Biotechnological techniques have now been developed for winning sulphur from sulphide ores.

Selenium and tellurium are obtained in concentrated form from anode mud obtained in the electrdyticrefining of copper. Polonium is made artificially by neutron irradiation of  bismuth in a nuclear reactor.