What is the History of Chlorine?
It was in 1774 when a Swedish chemist named Carl Scheele discovered the element Chlorine when he mixed powdered pyrolusite into muriatic acid. Chlorine gained its name from the Greek word "Khloros", which means "green". Chlorine is also used for the production of numerous products, across all segments. Some plastics can contain over 50% chlorine by volume. Just about any manufactured product uses chlorineat one step along the way. Chlorine is also used in many industries for disinfection or sanitizing of surfaces, equipment or aqueous solutions,including pool water.
How Chlorine is Made?
Chlorine is produced by the electrolysis of salt water. When electricity is passed through 2 NaCl (salt) and 2H20 (water), the atoms dissociate into Cl2 (chlorine) + 2 NaOH (Sodium Hydroxide) + H2 (Hydrogen). When using a salt chlorine generator on a pool, the pool chlorine is created by the salt cell, a stack of electrically charged plates. When power is applied to these cells, and salty water is pumped through the cell, chlorine is created instantly as the water leaves the salt cell and is pumped into the pool. In the manufacture of chlorine, Cl2 is isolated in its gaseous form, and used to create other chlorine compounds used for bleaching or disinfecting. The gas is passed over salts or bubbled through water to create a base product that can be packaged in granular, tablet or liquid forms.
How much Chlorine is Needed?
Swimming pools require a constant level of chlorine in the water at all times. The moment that chlorine drops below 1.0 ppm, algae and bacteria begin to thrive.1.0 ppm is a generally accepted minimum for public pool health standards, however recent studies have suggested that cyanuric acid in the pool water has a suppressive effect on the mobility and strength of free chlorine molecules. For this reason, some experts now recommend higher levels of free chlorine be used, from 3-6 ppm, rising with increasing levels of cyanuric acid from 30-60 ppm. Most backyard pools should operate with 2-4 ppm of free chlorine, although the use of mineral purifiers or ozonators can cut the chlorine demand in half. Trichlor tablets are used to maintain the normal daily operating level, and most pools will use 2-3 tablets per 10000 gallons, per week, to achieve proper levels.
How Does Chlorine Work to Sanitize?
When chlorine is added to water,another dissociation occurs. When we add Cl2 (chlorine) + H2O (water), we get a reaction which leaves us with HOCl (hypochlorous acid) + HCl (hydrochloricacid). How much of each is created is dependent on water temperature, cyanuric acid level and especially on water pH. Hypochlorous acid is the active, killing form of chlorine. This is what does the real sanitizing work in your pool water. The chlorine molecule or ion kills microorganisms by slashing through the cell walls and destroying inner enzymes, proteins and processes. When this occurs, the cell has been deactivated, or oxidized. The hypochlorous molecule continues this slash & burn until it combines with a nitrogen or ammonia compound, becoming a chloramine, or it is broken down into its component atoms, becoming deactivated itself. Some amount of chlorine will also gas off from an uncovered pool.