What is the percentage of available chlorine in chlorine gas?

Chlorine gas is considered to have a percentage of available chlorine at 100%. This means that when chlorine gas is used for disinfection and other water treatment purposes, it is in its pure form and fully available for reaction. The term "available chlorine" refers to the amount of chlorine that can effectively participate in chemical reactions, such as disinfection. Since chlorine gas is not diluted or mixed with other substances, it is wholly available for these processes.

In contrast, other forms of chlorine, such as sodium hypochlorite or calcium hypochlorite, contain lower concentrations of available chlorine, as they consist of compounds that release chlorine during their degradation or reaction processes. Therefore, an understanding of chlorine gas being at 100% availability is critical in water treatment applications, as it helps operators accurately gauge dosing requirements and disinfection efficacy.