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Analysis of Arsenic(III) Phosphate (AsPO₄)

Qualitative analysis

How to do salt analysis · Viva · Quiz

Aim

To analyse the given inorganic salt for one acidic and one basic radical.

Preliminary Test

  • Colour: White
  • Odour: Odourless
  • State: Crystalline solid
  • Solubility: Insoluble in water

Test of Anion (PO₄³⁻)

ExperimentObservationInference
Confirmatory Test
Ammonium Molybdate Test
Acidify with conc. HNO₃ and add ammonium molybdate solution, boil		Canary yellow precipitate is formedPO₄³⁻ is confirmed

Test of Cation (As³⁺)

ExperimentObservationInference
Original solution + H₂S gas in presence of dil. HCl and NH₄ClYellow precipitate is formedGroup-II-B (As³⁺) may be present
Confirmatory Test
Ammonium Molybdate Test
Treat the dissolved precipitate with concentrated nitric acid and ammonium molybdate solution		Canary yellow precipitate is formedPresence of As³⁺ is confirmed

Result

The given salt contains As³⁺ as the cation (basic radical) and PO₄³⁻ as the anion (acidic radical). The salt is Arsenic(III) Phosphate (AsPO₄).

Precautions

  1. Handle the chemicals with care.
  2. Don't use excess of chemicals.
  3. Keep the mouth of the test tube away from the face.