Aroclor is a trademark, registered to Monsanto Corporation, for naming mixtures of individual chlorinated biphenyls and chlorinated polyphenyls. Monsanto Corporation was the major producer of Aroclors from 1930 to 1977. Aroclors were used in a wide variety of applications, including dielectric fluids in capacitors and transformers, heat transfer fluids, hydraulic fluids, lubricating and cutting oils, and as additives in pesticides, paints, copying paper, carbonless copy paper, adhesives, sealants, and plastics. Each Aroclor is assigned a four digit number. The last two digits indicate the approximate percentage in weight of chlorine in the product, and the first two digits indicate the type of material as follows: 12 -- chlorinated biphenyls, 25 -- blend of chlorinated biphenyls and chlorinated terphenyls (75:25), 44 -- blend of chlorinated biphenyls and chlorinated terphenyls (60:40), and 54 -- chlorinated terphenyls.