During wet-process ortho-phosphoric acid manufacture via hydrochloric acid leaching (forming CaCl2 in solution), which solvent is used to extract H3PO4 from the CaCl2 liquor?

Introduction / Context:
In variants of the wet-process route employing hydrochloric acid to digest phosphate rock, calcium ends up as CaCl2 in solution alongside phosphoric acid. Solvent extraction can separate H3PO4 from CaCl2 brine. Recognising the appropriate solvent is a staple process-chemistry question.

Given Data / Assumptions:

• Leaching medium: hydrochloric acid → CaCl2-rich liquor.
• Target: extract H3PO4 into an organic phase.
• Candidate solvents: lower alcohols and hydrocarbons.

Concept / Approach:
Isopropanol (iso propyl alcohol) forms extractable complexes/associates with phosphoric acid and is miscible in ways that permit phase separation with salt-laden aqueous phases; hydrocarbons like hexane/toluene are poor for polar acid extraction. Butyl alcohol may be used in some systems, but the canonical choice for this wet-process step is isopropanol.

Step-by-Step Solution:

Verification / Alternative check:
Process descriptions and exam keys cite isopropanol extraction for H3PO4 from CaCl2 solutions, enabling subsequent solvent recovery and acid concentration.

Why Other Options Are Wrong:

• Butyl alcohol: less typical choice in this context.
• Toluene/hexane: insufficient polarity for strong acid extraction.
• Acetone: miscibility issues and not standard for this operation.

Common Pitfalls:
Overlooking the salt-out effect of CaCl2; appropriate polar solvent selection is critical for phase disengagement.

Final Answer:
Iso propyl alcohol (isopropanol)