ApuIse-radiolytic study shows that the anion of biphenyl decayed in liquid methyla~ mine via a first order process. The absorptions at 410 and 640 nm both decyed With the same rate ­constant. k is (2.4 :t 0.3) x 105 i1 in the concentration range 1.16 x 10- •.. 5 x 10-2 mol dm-3 of biphenyl. \iowever, in a 5 x 10-4 mol dm-3 solution of biphenyl 1 k is (1.1 :t 0.06) x 105 i1• The anion of pyrene showed an absorption spectrum With a maximum at 490 nm. It decayed by a second order process haviJ}g 2k:: (3.5 :t 0.4) x 105 e490 dm3 mor1 i1• When a solution ofpyrene contain­ing 10-3 mol dm-3 methylamine hydrochloride was irradiated, the order of the decay remained un­changed, but 2k was reduced to (1.3 :t 0.2) x 105 e490 dm3 mol:1 i1•