Yes, bromine is very heavy, but the load limit of the car is only 60,000 pounds as best as I can read it. Weight of load is roughly 1/3 of that of a nominal 100 ton car.
Car is still listed in UMLER, however it is not legal in Interchange Service. Outside length of the car is 29 feet 2 inches. Its allowed maximum weight on rail is 108K pounds.