For Example Swimming Pool pH

Swimming pool chemistry is fairly convoluted and we will be probing more as we go along. But before going off the deep end, we will consider pH here and how it affects swimming pool chemistry. 

Scale is a rock-hard crust that can form in pipes and pots that are used with hard water. Before the general availability of household water softeners, scale was a much more common experience. Insoluble scale forms from calcium ions when carbonate ion is present. This fact highlights, once more, the versatility of carbonates. We have seen carbon dioxide form carbonates and hence carbonic acid in water we have used sodium bicarbonate (baking soda) as a base and finally we have pointed out that carbonates can make fairly insoluble solids. These many talents of the carbonate ion make baking soda good for more than cooking. Baking soda makes an excellent deodorizer because it can react with both acidic and basic smelly compounds and can form nonvolatile, and hence non-smelly, compounds with many more. A lot of chemistry in a little box  

Some calcium and other minerals are found naturally in any water that has percolated through the ground. So if the swimming pool is allowed to become too alkaline, it will grow cloudy, at best, with suspended particles of insoluble salts or encrusted with growths of scale at worst. This appearance of a solid in a liquid solution is called precipitation, just as rain is called precipitation, because of the propensity of the solids to come out of the solution just as rain comes out of the sky. 

In the next chapter, we look at some other solid-forming solutions, as well as some whys, wherefores, and useful applications of these crusty precipitation reactions. 

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