Tennessee Valley Authority

Guerry H McClellan

John F McCullough

John F Phillips

A method of selectively extracting calcite and dolomite away from apatite in phosphate rock or phosphatic limestone wherein the phosphate rock or phosphatic limestone is treated with a mixture of sulfur dioxide, water, and a carbonyl compound. Solids are separated from the liquid phase. The solids consist principally of apatite admixed with clay, quartz, and other accessory minerals originally in the rock. The solids are heated to drive off adhering sulfur dioxide, water, and carbonyl. The liquid phase consists of carbonyl, water, sulfur dioxide, and magnesium and calcium ions. Heating this liquid preferentially precipitates CaSO.sub.3.1/2H.sub.2 O. This solid is filtered off and the filtrate further heated to precipitate MgSO.sub.3.3H.sub.2 O largely free of CaSO.sub.3.1/2H.sub.2 O. All off gas and filtrate is returned to the process.

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Killen, AL, United States of America

Guerry H McClellan