This page contains a list of common Aroclors. The numbering standard for the different Aroclors is as follows:

• The first two digits usually refer to the number of carbon atoms in the phenyl rings (for Polychlorinated Biphenyls this is 12).
• The second two numbers indicate the percentage of chlorine by mass in the mixture. For example, the name Aroclor 1254 means that the mixture contains approximately 54 percent chlorine by weight. 

• Table of Aroclors (PDF)(1 pg, 11 K)