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If such a 7.5 grain water is used in the home for washing purposes, the positive calcium and magnesium ions react with the soap used to produce insoluble soap curds.
It is these insoluble soap curds that produce the ring around the bathtub, the half-clean, dingy-looking clothes, etc.
Again, if such water is brought into the home or factory and heated or boiled, the bicarbonate anions revert to their carbonates, which combined with calcium and magnesium produce scale on the walls of the container or in the piping system.
In a manner of speaking, scientists working out the problem of eliminating hardness minerals from a water supply applied the cause of the problem in obtaining the solution.
They reasoned that if some ions not contributing to hardness could be introduced into a water supply as a replacement for the calcium and magnesium ions, water could be made totally soft, totally useful. The result was the ion exchange process for treating hard water. (--> Next)