It looks like its connected to the cast iron waste pipe with a threaded adapter. Pipe wrench won't bite, it just slides around. Would a chain wrench work on a chromed trap pipe? Any secrets to this? It's been in there 40 years probably.
The trap (part on the right of the photo) looks like it's connected using lead. That doesn't look like a threaded connection.
I'd cut it off with a sawzall about 1/4" away from the hub, cut it on the inside almost through to the threads in three places and then collapse it to remove it.
Then clean the threads before inserting a new trap adapter.
The method that snoonyb talks about is probably the only way to do it.
You can cut it just once and then use a chisel to collapse it at the cut also. When I've had to do that, I've used a manual hacksaw blade in a holder so I don't overdo the cut into the female fitting too much.
It does look like it's caulked with lead but it looks like it's attached that way to a threaded adapter. if i can get it out of the adapter with a torch, is there a fernco donut that would work to attach a new trap? If not I'll try cutting and chiseling as suggested. Thanks.
The trap will be of a softer metal and will response easily to heat.
However there are a couple of downsides to a torch;
The joint may have been silver soldered, which will require a hotter burning gas, than NAP.
So, unless you use a heat sink, (a wet towel), and are quick, can allow the heat to migrate to the cast hub causing it to fracture.
Yes there are the appropriate size no-hub couplings.
Which in the end, may be a simpler solution.
Remove some more of the wall to the right in the photo to investigate removing and replacing the whole assembly, all of which can be accomplished with fernco's. and ABS fittings.
Your time, your money