`  == Confusion with calcium hypochlorite == Whoever wrote:  :High-test hypochlorite (HTH) is sold for chlorination of swimming pools and contains approximately 30% sodium hypochlorite. The crystalline salt is also sold for the same use; this salt usually contains less than 50% 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.  `