Estimating the amount of free chlorine in water: Chlorine is found in natural water because salt deposits dissolve in it, roads are salted to melt snow and ice, chemical industries dump waste water, wells run, garbage disposals, irrigation drainage, refuse leachates pollute the water, and seawater gets in along the coast. Chlorine ions can thus react with NH and various organic and inorganic compounds contained in water and wastewater. This will result in complex reactions by producing a combination of residual chlorine compounds. Both free chlorine and its compounds that exceed certain limits will be very dangerous for human consumption.
This can be analyzed using several different methods, some of which are:
- Argentometric titrimetric method.
- Iodometric titrimetric method.
- Gravimetric determination.
- Ion selective electrode method.
AgNO + NaCl = AgCl +NaNO
K₂CrO, + 2CAgNO, Ag₂ CrO, + 2KNO,
At the end point of the titration, if there is no more free chloride left, add one drop of AgNO titrant so that Ag Cro will be formed, resulting in a pink or red-colored endpoint.
Atau mg cl/L= (X x N
x 35450)
N = normality of AgNO₂
Theory:
Cl₂ + 2KI -> 2KCI+l₂
KI
+1₂
-> Kl3
I2+2Na2
S2 03 ->
2Nal + Na2S4O6
Procedure
This process is referred to as iodometric titration because it uses 1 indirectly for titration. To about 500 ml of sample, add about 5 ml of acetic acid and 1 g of Kl. Put on the stopper, shake vigorously, and leave for some time. Thus, all will be liberated. Next, the L is titrated with a solution of Na.50, a standard with a concentration of 0.025 N, using starch as an indicator. The end point is the color change from dark blue to colorless.
1 ml 0,025 N Na2S2O3 = 0,4 mg Cl2
Calculation: mg cl/L = (X x N x 35450)
sample volume (ml)
with
:
V=
Volume Na2S2O3
N= Normality Na2S2O3
This method generally uses a solution with a concentration containing free chlorine of 40 ppm or more.
3. Alkalinity
The alkalinity of water is a measure of the acid-neutralizing ability of the water. Alkalinity in wastewater arises due to the presence of titrable bases such as hydroxides, carbonates, and bicarbonates. bases such as hydroxides, carbonates, and bicarbonates.
[OH]+H -> H2O
[CO2]+H -> [HCO2]
[HCO3]+H -> H2O+CO2
Alkalinity is measured by titrating the sample with a standar
Acid such as N/50 H2SO4 The results are expressed as CaCO3. The value of alkalinity depends on the pH and the end point marked in the titration.
pH value |
Indikatoir used |
End Point |
8,3 |
Phenolphthalein |
Colored Dots |
4,4 |
Methlorange |
Warna merah |
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