Chloride is a major constituent of sea water and is extremely corrosive in acidic environments. Chlorides may also get into surface water from several sources including:
1) rocks containing chlorides;
2) agricultural runoff;
3) wastewater from industries;
4) oil well wastes;
5) effluent wastewater from wastewater treatment plants, and;
6) road salting.

Therefore, water that is used in industry or processed for any use has a recommended maximum chloride level. It requires close monitoring in applications such as boiler systems, close loop cooling water systems, cooling towers etc.

APPARATUS

................1 Test Tube.........................Code.........................0778
................1 Titrator............................. Code....................... 0378

REAGENTS

..............Chloride Reagent.1......................Code......................4504 - E
..............Chloride Reagent.2......................Code......................4505 - H
..............Phenolphthalein Reagent..............Code.......................2246 - E
..............Sulphuric Acid Reagent (0.5 N.)..Code.......................6090 - E

PROCEDURE

1. Fill the Test Tube (0778) to 15 ml level with water sample.

2. Add one drop of Phenolphthalein Reagent (2246 - E) to the sample. If the solution remains colourless proceed directly to step 3. If the sample turns red, add Sulphuric Acid (6090 - E) one drop at a time until the red colour disappears. Then proceed to step 3.

3. Add three drops of the Chloride Reagent No.1 (4504 - E) to the sample in the Test Tube. Insert the Test Tube Cap and shake to mix. A yellow colour will result.

4. Fill Titrator with the Chloride Reagent No. 2 (4505 - H) to the 'Zero' mark in the Test Tube Cap. Then add to sample drop by drop, shaking gently, until the yellow colour is permanently changed to pink / brown.

5. Result is obtained in p.p.m. Chloride by multiplying Titrator reading by ten.