Dichlor and trichlor are both stabilized chlorine, meaning that they are both sources of chlorine that also contain cyanuric acid.
Dichlor is a white granular, fast dissolving, near pH neutral chlorine compound, which provides either 56 or 62 percent available chlorine, depending on which is purchased. It can be used for regular as well as super chlorination. For every 10 ppm free chlorine that it adds to a swimming pool, it also adds 9 ppm cyanuric acid.
Trichlor is a white granular very slow dissolving and acidic source of chlorine with a pH between 2.8 and 3. Because it is slow dissolving, it is designed to be used in floating chlorinators, erosion feeders, and automatic in-line or off-line chlorinators. It cannot be used for super chlorination because of its slow dissolve. It provides 90 percent available chlorine, the highest of the any chlorination compound. For every 10 ppm free chlorine that it adds to a swimming pool, it also adds 6 ppm cyanuric acid.