The term chlorine is generally used for disinfection in swimming pools, domestic water and cleaning, and the chemical substances used by housewives to make laundry more white.

When the chlorine ion which is not found in water under natural conditions but mixed with water as a result of various activities is measured, the value obtained is called free chlorine amount. Chlorine ion gives disinfection of oxygen ions. This reduces the amount of free chlorine in the water. That is, free chlorine ions oxidize many substances present in the water and consequently the amount of free chlorine in the water is reduced, or completely destroyed. Sometimes free chlorine is also called active chlorine.

Free chlorine is required to prevent the destruction and proliferation of microorganisms that reach the water distribution networks in one way. Otherwise, various diseases may occur depending on the consumption of these waters.

The Regulation on Water for Human Consumption issued by the Ministry of Health regulates the principles regarding the compliance of water for human consumption with technical and hygienic conditions, ensuring the quality standards of water, production, packaging, sale and inspection of spring waters. According to this regulation, the amount of free chlorine in waters should be maximum 0,5 mg / l. According to World Health Organization standards, free chlorine concentration in tap water should be at least 0,2 mg / l.

Free chlorine determination in water is carried out in authorized laboratories. The standards considered in these studies are as follows:

• TS 5489 EN ISO 7393-1 Water quality - Determination of free chlorine and total chlorine - Part 1: Titrimetric method
• TS 6229 EN ISO 7393-2 Water quality - Determination of free chlorine and total chlorine - Part 2: Colorimetric method for routine controls
• Water quality - Determination of free chlorine and total chlorine - Part 6230: Iodometric titration method for determination of total chlorine TS 7393 EN ISO 3-3