Chlorine is a chemical element; it has 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.Cl2, Saturated Solution is a standardized, ready-to-use laboratory reagent, typically a solution of chlorine gas (Cl2) dissolved in water to a specific concentration (approximately 0.4% w/v) and pH, primarily used in pharmaceutical and life science quality control to prepare precise solutions for chemical analysis, such as volumetric titrations.