Confusion with calcium hypochlorite  Whoever wrote  Hightest hypochlorite HTH is sold for chlorination of swimming pools and contains approximately  sodium hypochlorite The crystalline salt is also sold for the same use this salt usually contains less than  of sodium hypochlorite However the level of active chlorine may be much higher  is confused  These statements describe calcium hypochlorite and should not be in this article  Active chlorine is an industrial term giving the relative performance in chlorinating power compared to an equal mass of elemental gas chlorine  It does not directly relate to the purity of the product