Aquarium & Aquaculture

Chlorine is a chemical element with symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is a yellow-green gas at room temperature. It is an extremely reactive element and a strong oxidising agent: among the elements, it has the highest electron affinity and the third-highest electronegativity, behind only oxygen and fluorine.
The most common compound of chlorine, sodium chloride (common salt), has been known since ancient times. Around 1630, chlorine gas was first synthesised in a chemical reaction, but not recognised as a fundamentally important substance. Carl Wilhelm Scheele wrote a description of chlorine gas in 1774, supposing it to be an oxide of a new element. In 1809, chemists suggested that the gas might be a pure element, and this was confirmed by Sir Humphry Davy in 1810, who named it from Ancient Greek: χλωρός khlôros “pale green” based on its colour.

Chlorine is normally present in water as hypochlorous anion and is removed by strong base anion resins.

(Sodium) hypochlorite is widely used as a bleaching agent; in water treatment as a disinfectant. It is the strongest oxidant among the oxo-chloride series, chlorite, chlorate, or perchlorate.

Often used after a reverse osmosis system, a color-changing mixed bed DI resin offers the user a simple method of water purification and monitoring.

Aquatic life is very sensitive to changes in pH or inorganic ion content. Maintaining stable levels is important to optimize these systems.

Hardness ions, comprised of calcium and magnesium, can cause scaling of heated surfaces and shorten the life of appliances such as hot water heaters, dishwashers, and washing machines. The presence of hardness in water leads to greater soap consumption in laundry and cleaning operations.