PROTOCOL N° 9

IDENTIFICATION OF PO43- IONS IN AN AQUEOUS SOLUTION

ATTENTION: The nitric acid solution used in this work is an extremely corrosive substance; its vapours are highly toxic affecting the eyes and the respiratory system; avoid inhaling and spilling.

Risk code(s): R 35
Safety code(s): S 18, 25, 26, 27, 28, 37

REAGENTS

  • Aqueous solution of ammonium molybdate, 0.5 mol/dm3 (NH4)2MoO4 solution
  • Aqueous solution of nitric acid, 6 mol/dm3 HNO3
  • Phosphate test solution

PROCEDURE

  1. Identification of PO43- in a test solution

    2. 1.1  Place 10 drops of the phosphate test solution in a test tube,

    1.2  Acidify the solution with 8 drops of the nitric acid solution,

    1.3  Heat the solution moderately for 1 minute,

    1.4  Stop heating the tube and add 12 drops of the molibdate solution,

    1.5  Let the test tube containing the solution rest for 5 minutes,

    1.6  Record the observations.

  1. Verification of the eventual contamination of a water sample by PO43-

    2. 2.1  Place 10 drops of the water sample in a test tube,

    2.2  Repeat the procedure as described in 1.2.-1.6.

CONCLUSIONS

Does the analyzed water contain PO43-, Yes or No ?