Chlorine — Nature’s miracle

In the fight against the recent coronavirus pandemic, chlorine bleach has emerged as a true winner due to recommendations from the Centers for Disease Control (CDC), the Environmental Protection Agency (EPA) and the World Health Organization (WHO).This powerful chlorine compound has a proven track record to safely remove both bacteria and viruses from surfaces and from the water. The CDC has stated “there is no evidence that Covid-19 can spread to people through the water used in pools, hot tubs or water playgrounds. Proper operation and disinfection of pools, hot tubs and water playgrounds should kill the virus that causes Covid-19.”In the pool industry, liquid chlorine, or sodium hypochlorite, has long been recognized as one of the most effective tools for achieving clear and sparkling algae free water. In more recent years, alternative sanitizers have been developed for those opposed to chemical use. But with the reality of Covid-19, the simplicity and relative cheapness of bleach use has caused it to fly off the shelves.Bleach, or sodium hypochlorite, has the great benefit of being able to both sanitize and disinfect, which may sound like the same thing, but the two words have slightly different definitions.According to theAmerican Chemistry Council- “‘Sanitizing’lowers the number of germs on a surface or object by reducing the germs to levels considered safe by public health standards or requirements. ‘Disinfecting’ however, kills germs by using antimicrobials directly on surfaces and objects”.When added to water, sodium hypochlorite forms a powerful antimicrobial molecule called hypochlorous acid.NaOCl + H2O → NaOH + HOClHypochlorous acid is effective at inactivating up to 99.9% of bacteria in water. At the proper dilution, it also works to disinfect surfaces to remove microbes.Making Sodium HypochloriteSodium hypochlorite or liquid bleach, was developed in 1785 by frenchman Claude Louis Berthollet. His original method involved passing chlorine gas (Cl2) through a sodium carbonate solution, but the resulting solution of sodium hypochlorite was weak.Hasa, Inc., a leading producer and distributor of high quality water treatment solutions, makes use of the chlor alkali process to manufacture their sodium hypochlorite. This process uses table salt, or sodium chloride as a basis for the sanitizer.Specifically, water is added to salt to make brine, which is then filtered for purity. In a cell room, electricity is applied to the brine to break it up into sodium hydroxide (NaOH) chlorine (Cl2) and hydrogen gas. This is then sent to Hasa’s plants by rail car and tanker trucks.At the plants, chlorine is mixed with sodium hydroxide, resulting insodium hypochlorite, salt and water. These plants operate under tight controls to produce varying strengths of sodium hypochlorite.The overall chemical reaction is:Cl2 + 2NaOH → NaOCl + NaCl + H2O + heator, chlorine + sodium hydroxide (caustic soda) → sodium hypochlorite + sodium chloride + water + heat.One of the differences in the way Hasa produces sodium hypochlorite is in the high-pressure filtration process. Because the raw materials are earth mined, they contain certain metal impurities. Hasa uses a triple filtration system to remove some of these impurities, such as copper, iron, nickel and metal. These impurities are part of what causes sodium hypochlorite to lose its strength.StabilitySodium hypochlorite is unstable and has a limited shelf life, meaning that the chemical will decompose and the available chlorine will decrease over time.Time, temperature, pH and exposure to light are some of the major factors that also affect its stability.The Chlorine Institute developed a formula for estimating the concentration of sodium hypochlorite stored at a temperature of 80°F at a starting concentration of 13% (see table).After 45 days, for example, 13% sodium hypochlorite will decompose to just over 10%. For this reason, it is a good idea to p