Potomic tracon KPHL to KIAD

[philacop]

HI
Does anyone know what freq is switched to when a flight is on 126.100 at MULRR on approach to dulles from phl intl. Also when departing dulles to phl intl what freq is the departure freq after the tower hands off as Iam to far to receive the planes at the low alltitudes in phila
thanks

[EMD91123]

I know after 126.1 they are handed off to 125.8(final). The return trip from IAD-PHL is as far as I remember 125.05-128.7-124.55-then i cant remember. Thats what I recall from my days up North.