How is phosphoric acid made from calcium phosphate and sulfuric acid?

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The structure of phosphorous acid, H3PO3. — oxyacid The structure of phosphorous acid, H₃PO₃.

Phosphoric acid ( $H_{3} P O_{4}$ ) is commonly produced by treating calcium phosphate ( $C a_{3} (P O_{4})_{2}$ ), typically found in phosphate rock, with concentrated sulfuric acid.1

The chemical reaction for this process is as follows:

$C a_{3} (P O_{4})_{2} + 3 H_{2} S O_{4} \to 2 H_{3} P O_{4} + 3 C a S O_{4}$

Following the reaction, the resulting mixture is diluted with water, and the insoluble calcium sulfate ( $C a S O_{4}$ ) is removed through filtration. The resulting phosphoric acid is often contaminated with calcium dihydrogen phosphate and other impurities present in the naturally occurring phosphate rock.1