Fmc Corporation

Jeffrey C Dore

Harvey Rosenhouse

Richard E Hall

David P Brochu

The invention is a process to purify a solution of phosphoric acid by removing transition metal impurities such as iron, chromium and vanadium. In the process a solution of phosphoric acid in an organic solvent which is substantially immiscible with water is contacted with an aqueous solution of a salt of an alkali metal of phosphoric acid. The phosphoric acid recovered following the contacting contains a substantially lesser content of transition metal impurities.

Process for purifying phosphoric acid

A continuous process for reducing the arsenic content of phosphorus is described in which the impure phosphorus is continually passed through a heat exchanger and heated to vaporize a portion of the phosphorus at a temperature not above 200.degree. C., separating the vaporized phosphorus in a disengaging zone under subatmospheric pressure and introducing it into a fractionating zone under subatmospheric pressure, fractionating the phosphorus from the less volatile arsenic, condensing under subatmospheric pressure low-arsenic phosphorus rising from the fractionating zone, returning a portion of the low-arsenic phosphorus condensate as reflux to the column, removing high-arsenic liquid phosphorus as bottoms from the fractionating zone, and recovering the remaining portion of low-arsenic phosphorus condensate as product.

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Hamilton Square, NJ, United States of America

Jeffrey C Dore