Chemistry of inorganic compounds – Phosphorus or compound thereof – Oxygen containing
Reexamination Certificate
2005-03-01
2005-03-01
Langel, Wayne A. (Department: 1754)
Chemistry of inorganic compounds
Phosphorus or compound thereof
Oxygen containing
C423S316000, C423S317000
Reexamination Certificate
active
06861039
ABSTRACT:
The present invention provides a purification method of phosphoric acid, which includes bringing phosphoric acid containing arsenic into contact with hydrogen halide, thereby to remove the arsenic from the phosphoric acid, and a purification method of phosphoric acid, which includes bringing phosphoric acid containing arsenic into contact with hydrogen halide in the presence of a compound capable of generating hydrogen halide under acidic conditions. According to the method for purifying phosphoric acid of the present invention, a completely new method for removing arsenic in phosphoric acid is provided, which does not require a filtration or deaeration step or shows a great amount of residual sodium, unlike a sulfide coagulation method. This method is applicable to high concentration phosphoric acid, particularly polyphosphoric acid, and can be practiced at a low cost. In addition, a conventionally nonexistent high purity polyphosphoric acid having an arsenic (As) content of not more than 1 ppm and low contents of heavy metal, silica, sodium and the like can be provided.
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Hotta Kiyoshi
Kubota Fuyuhiko
Langel Wayne A.
Morrison & Foerster / LLP
Toyo Boeski Kabushiki Kaisha
Wright, Sr. William G.
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