Here’s a explanation of how complexometric titration is used to measure water hardness:
1. What it measures:
- Water hardness is caused by calcium and magnesium ions in water.
- These ions make water “hard,” affecting soap usage and pipes.
2. How it works:
- A chemical called EDTA is added to the water. EDTA binds very strongly to calcium and magnesium.
- An indicator (usually Eriochrome Black T) is also added, which changes color when all the calcium and magnesium are bound by EDTA.
3. The process:
- You slowly add EDTA to the water sample while stirring.
- At first, the indicator shows one color (like red), showing that calcium and magnesium are still free.
- As EDTA binds all the ions, the color suddenly changes (to blue). This shows the endpoint—all hardness-causing ions are captured.
4. Result:
- The amount of EDTA used tells how hard the water is.
- More EDTA means more calcium and magnesium, so the water is harder.
In short:
Complexometric titration is a simple and reliable method to find out how much calcium and magnesium are in water by using a chemical that grabs these ions and a color change to show when the job is done.