Liquid chlorine is sodium hypochlorite (a chlorine compound) dissolved in a solution of water. Because it is dissolved in water it typically has a 12½% active content. The advantage to liquid is that it is quickly available – as soon as you pour it into the pool. There’s no mixing with water, no brushing to dissolve chlorine sitting on your liner. This is particularly useful when trying to rid a pool of algae. You want something that will work quickly and effectively. For this reason liquid chlorine is your best alternative for combating active algae. Some people choose to do their routine shock with liquid due to ease – just pour and go.