A relation between the limiting viscosity number and the initiattor concentration for the polyacrylonitrile and polymethyl acrylate has been drived as this : Uj] = A / [I ]a For this purposes the purified acrylonitrile has been. polyme- rized by using Bz2O2 as the initiator. The limiting viscosity num- bers of this polymer have been measured. The experimental data for the polymethylacrylate have been taken from reterence [1]. By plotting the limiting viscosity numbers against the concen¬tration of the initiator used, a relationship showing the variation of the limiting viscosity number with the initiator concentration has been obtained.