Some like it hot, but most would prefer to go swimming! That’s our thought as the summer heat churns on, and we seek a reprieve at the local swimming pool. In fact, it was in that spirit as we contemplated the International Year of Crystallography and our #CrystaloftheWeek. The obvious choice was that bright yellow white crystal that keeps so many pools around the world sanitized and beautiful: calcium hypochlorite.
Ah yes, it smells just like the bleach used to whiten and brighten your t-shirts and disinfect your shower tiles because all these products contain calcium hypochlorite or other iterations of chlorine. Calcium hypochlorite is used for water treatment, whether it’s drinking water or swimming water. Because the compound is highly polar, it dissolves relatively well in water, which is also polar. During this process, the hypochlorite ions actually react with the water molecules, forming hypochlorous acid. This acid form reacts strongly with organics, such as bacteria, to keep water from harboring dangerous microbes that can be harmful to human health. This characteristic is also why you can sometimes find calcium hypochlorite in moss and algae removers, as well as weedkillers.
Generally, commercial calcium hypochlorite is sold in a hydrated form, which means that water is added to the compound, mixed with various other impurities. This added water helps prevent spontaneous combustion of the calcium hypochlorite, which is a strong oxidizer, in cases of accidental mixture with a fuel source. The downside of using calcium hypochlorite in pools is that direct exposure to harsh ultraviolet radiation causes the chlorine to “boil” off in gaseous form more quickly. To enhance the longevity of calcium hypochlorite as a disinfectant in outdoor pools, cyanuric acid is often added as a stabilizer.
Despite being commonly used in drinking water (in small amounts!) and its ability to help keep pools sanitary, calcium hypochlorite can be dangerous to skin, eyes and one’s respiratory system, meaning that anyone who works with it must handle it with care. That’s why you should never store calcium hypochlorite in a used container that once held grease or paint, no matter how clean it looks!
Photo credit: Wikimedia Commons