How can soap make soft water from hard water? What objections are there to using soap for this purpose?
The only way I know of is to use enough soap to precipitate all of the "hard" stuff in hard water; namely, the calcium and magnesium salts (primarily) with added amounts of iron, manganese, etc. This forms a soap scum which floats on top of the water. Frankly, I've never heard of using soap to "make water soft." There may be other ways of which I'm unaware.
Soap can help make soft water from hard water through a process called saponification. Hard water contains high levels of minerals such as calcium and magnesium ions, which can interfere with the effectiveness of soap. However, soap contains a molecule with a hydrophilic (water-loving) head and a hydrophobic (water-repellent) tail. When soap is mixed with hard water, the calcium and magnesium ions react with the soap molecules to form an insoluble substance called soap scum, which reduces the effectiveness of the soap.
To address this issue, various methods can be used to soften hard water before mixing it with soap. One commonly used method is water softening through ion exchange. This involves passing hard water through a resin bed containing sodium ions. The resin beads attract and exchange the calcium and magnesium ions with sodium ions, effectively softening the water.
There are a few objections to using soap for this purpose:
1. Formation of Soap Scum: As mentioned earlier, when soap is used with hard water, it forms soap scum, which can leave a sticky residue on surfaces, clothes, and skin.
2. Reduced Cleaning Efficiency: Soap is less effective in producing a lather and cleaning in hard water, resulting in the need for more soap to achieve the desired cleaning effect.
3. Increased Water Usage: Since soap is less effective in hard water, more water may be required to rinse off soap residues, leading to increased water usage.
4. Environmental Impact: The excess soap and detergents used due to hard water can contribute to increased pollution in water bodies, potentially harming aquatic life.
Overall, while soap can partially work with hard water, it has limitations, and it is more effective to use water softening techniques to obtain truly soft water.