Introduction
Titration is a process of chemical analysis in which the quantity of some constituent of a sample is determined by adding to the measured sample an exactly known quantity of another substance with which the desired constituent reacts in a definite, known proportion.
Temporary hardness: It is a type of water hardness caused by the presence of dissolved bicarbonate minerals.
Permanent hardness: It is usually caused by the presence of calcium sulfate or magnesium sulfate, again for their phosphate.
Total hardness: The presence of temporary and permanent hardness (both) in water.
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Apparatus
1. Burette2. Pipette
3. Conical flask
4. Stand
5. Droppers etc.
Machine Description
1. There is a ring stand, connected with a burette with a clamp so that it can be up and down and easily moved.
2. At the bottom of the burette, there is a key for controlling the solution.
3. There is a conical flask attached to a burette so that solution can be passed easily from burette to flask.
Working Procedure
A) Preparation of 0.01 M EDTA Solution
The molecular weight of disodium salt of EDTA:
(CH2COOH)2 N2(CH2)2 (CH2COONa)2. 2H2O
=(12+1✕2+12+16✕2+1)✕2 +(14✕2) +(12+2)✕2 +(12+1✕2+12+16✕2+23)✕2 +2✕(2+16)
=118+28+28+162+36
=372 gm
Therefore,
In, 1 M solution of 1000 ml containing 372 gm EDTA
So, 0.01 M solution of 1000 ml contains (372✕0.01) gm EDTA
So, 0.01 M solution of 100 ml contains (372✕0.01✕100)/1000 gm EDTA
=0.372 gm
B) Preparation of Ammonia Buffer Solution
145 ml of liquor ammonia (NH4OH) +15 gm of (NH4Cl) + distilled water to make a 250 ml solution
The Figure for Total Hardness
 |
| Total Hardness of Water |
Working Process for Total Hardness
1. Add 2 ml of buffer solution to 100 ml of sample water.
2. Adding 3–4 drops of Eriochrome Black T indicator.
3. Titrating against 0.01 M prepared EDTA solution in burette until the color changes from violet to pure blue.
4. Calculated the total hardness in terms of PPM of CaCO3.
Table 1: For Total Hardness
Calculation 1: For Total Hardness
Total hardness = (Volume of 0.01 M EDTA solution in ml/Volume of sample water in ml)✕1000 ppm of CaCO3
The Figure for Permanent Hardness
 |
| Permanent Hardness of Water |
Working Process for Permanent Hardness
1. Sample water is taken at 100 ml.
2. By heating 100 ml to 50 ml for 30 minutes.
3. Filtering by removing temporary hardness.
4. Add distilled water of 50 ml and make it a total of 100 ml.
5. Add 2 ml of buffer solution.
6. Adding 3–4 drops of Eriochrome Black T indicator.
7. Titrating against 0.01 M prepared EDTA solution in burette until the color changes from violet to pure blue.
8. Calculated the permanent hardness in terms of PPM of CaCO3.
Table 2: For Permanent Hardness
Calculation 2: For Permanent Hardness
Permanent hardness = (Volume of 0.01M EDTA solution in ml/Volume of boiled water taken in ml)✕1000 ppm of CaCO3
Now, Temporary hardness = Total hardness-Permanent hardness
Precautions
1. The machines (burette, conical flask, stand) setup should be stable and okay.
2. Calculation of the EDTA solution should be done carefully.
3. Must be careful about the timing of color change during titration.
4. Must be careful about the final and initial burette readings.
5. The calculation should be done carefully.
Tags
Pretreatment