PROTOCOL N° 6

AMOUNT OF CHLORIDE IONS IN A WATER SAMPLE

ATTENTION: Care should be taken not to spill the aqueous silver nitrate solution over the skin; protect your hands and eyes by using gloves and goggles.

Risk code(s): R 36, 38, 41, 43
Safety code(s): S 18, 25, 26, 37

REAGENTS

  • Aqueous solution 0.01 mol/dm3 AgNO3
  • Aqueous solution (5% m/v) K2CrO4
  • Universal indicator paper

PROCEDURE

  1. Place 10 mL of the water sample in an Erlenmeyer. Check the pH value and make sure it is between 6 and 9; correct if necessary,
  2. Add 5 drops of the potassium chromate solution,
  3. Counting the number of drops, add nitrate solution to the stirred water sample until the formation of a red precipitate,
  4. Record the results.

DATA TREATMENT

Calculate the concentration of chloride ions in the water sample with the help of the following equation:

cCl- / mg/L Cl- = n x 1.8

Where n is the number of drops of silver nitrate solution.