Chloride in the form of chloride ion (Cl-) is one of the major inorganic anions in water and waste water and in portable water. The salty taste produced by chloride concentration is variable and dependent on chemical composition of water.
The chloride content is higher in waste water than in raw water because of NaCl. Along sea – coast chloride may be presented in higher concentration. It may also be increased by industrial process.
High chloride content may harm metallic pipes and structures as well as growing plants.
The Argon to metric method is suitable for use in relatively clear water when 0.15 to 10 mg of Cl- is present in portion titrated.
The principle behind this method is that in neutral or slightly alkaline solution potassium chromate can indicate the end point or titration of chloride with silver nitrate precipitate sliver chloride quantitatively before red silver chromate is formed.
Bromine, iodine and cyanide register as equivalent chloride concentration, sulphide, thiosulphate and sulphite ions interfere but can be removed by treatment with H2O2.
- Wash all the glasswares with D/W.
- Fill burette with 0.014 N AgNO3 solutions.
- Take 10 ml sample in a flask and add potassium chromate as indicator.
- Titrate it against AgNO3 solution.
- End point will be yellow to reddish.
- Note down the BR and perform the necessary calculations.
PPM of Chloride = BR x 35400 x AgNO3
Ml of sample