Cloride (Cl-)

SPECIFICATIONS

Method           : Titration

Range              : Not Specific

Testing time    : Not Specific

Calculation      : ppm Chloride as NaCl = (20) (mL SO229 used – mL indicator blank)

                          The ppm as NaCl can be converted to ppm as Cl using the following formula:

                          Ppm as Cl = ppm as NaCl x 0.607

INTERFERENCES

The following ions may interfere when present in concentrations exceeding those listed below : Species            mg/L

PO₄                  25   mg/L

Fe                    10   mg/L

NTA                 100 mg/L

SO₃⁻²                20   mg/L

Br, CN⁻, I⁻, S⁻², all register as equivalent chloride.

Note: The S⁻² and SO₃⁻² interference can be removed by pretreatment with H₂O₂, and boiling. Use the following pretreatment in place of Step 2 of the Chloride procedure.

1)      Adjust the pH of the sample with H-6 (SO279) or N/50 Sulfuric Acid (S0226) until the sample just turns pink in the presence of the P-indicator (S0222) pH 8-9

2)      Add 2 mL of H₂O₂ (3% Hydrogen Peroxide can be obtained from a local drugstore) and stir vigorously for 1 minute. Samples containing sulfide should be boiled for 10 minutes after the H₂O₂ addition.

3)      After stirring, add N/50 Sulfuric Acid (S0226) until sample turns colorless, then proceed to Step 3 of the procedure.

PROCEDURE

1.      Measure 50 mL of clear supernatant or filtered sample into a casserole.

2.      Add 2 drops of Phenolphthalein indicator (S0222). If a pink color develops, add N/50 Sulfuric Acid (S0226) until the pink color is discharged.

Note: The pH of the sample must be between 7 and 10. If the solution does not turn pink after the addition of P indicator, the sample may betoo acidic. H-6 (S0279) should be added (1-2 drops at a time) until the sample turns pink. Then proceed with the addition of N/50 Sulfuric Acid (S0226) until the pink color is discharged.

3.      Add 2 mL of Potassium Chromate indicator (S0224).

4.      Mix

5.      Fill buret to zero mark with Silver Nitrate (S0229).

6.      Titrate with Silver Nitrate (S0229) until one drop turns the yellow solution a nonfading brick-red cast.

7.      Check the buret scale and record the number of mL that was used to cause the color change.

8.      Repeat the above steps on an aliquot of chloride-free distilled water to determine an indicator blank.

Cloride (Clˉ)

Titration Analytical Procedure

-          Sample : 50 mL

-          Add Indicator (460-SO222) three drops, Swirl to mix.

(If colour is Red, Alkalinity and pH is high)

-          Titration with Titrant (460-SO226) until colour change from Red to Colourless.

If colour is not Red ;

-          Add exactly 2 mL Indicator (460-SO224), Swirl to mix (Colour : Yellow).

-          Titration with Titrant (460-SO229) until colour change from Yellow to Orange/Redness.

-          Result (ppm CaCO3)  = Titrant used x 16

Note :

-          > 130 à Colour is not Orange

-          < 130 à Colour is Orange/Redness