Determination of Residual Chlorine

Determination of Residual Chlorine

 

Principle: In a neutral or slightly alkaline solution, Potassium Chromate can
indicate the end point of silver nitrate solution.Silver chloride is precipitated
Quantitatively before red silver chromate is formed.Estimation of chlorine by
this method is known as Argento metric Titration.
Reagents: * Potassium Chromate solution
* Standard Silver Nitrate Titrant
* Standard sodium chloride solution
Procedure:a) sample Preparation
* Use a 100 ml sample or a suitable portion diluted to 100 ml
* If sample is colored add 0.3 ml of Aluminium Hydroxide Al (OH)3
Mix, allow to settle & Filter
* If sulphide, sulphite, or thiosulfate is present add 1 ml of hydrogen
peroxide and stir for One (01) minute.
* Directly titrate samples in the pH range 7-10
* Add 1.0 ml of Potassium Chromate indicator solution
* Titrate with silver nitrate to a pinkish yellow end point
* Standardize Silver Nitrate Ag 2(NO)3 solution and establish reagent
blank value by Titration method. A blank of 0.2-0.3 ml is normal.
Calculations: Cl, mg/lit = (A-B) x 35450/ml of sample Where,
A = ml of titration for sample
B = ml titration of blank
N = normality of silver nitrate
NaCl, mg /lit = mg Cl /lit x 16.5
Precision Bias:Standard deviation was found to be 4.2%.