how to run a second copy of firefox in a separate address space with no connection to the first?

[Dan Hitt <dan.hitt@gmail.com>]

I would like to run a second copy of firefox in debian, that is
completely unconnected to the first.

That is, the second copy should not share history, cookies, any kind
of storage, passwords, configuration, or anything else with the first.
It should be possible to send a signal to one (such as kill) without
the other being aware of it.

In essence it should run parallel to firefox like a clone (e.g., Pale
Moon), except using the same binary.  (But i'd be willing to copy the
binary if there were an easy way to just change its name to firefox2
or something.)

I suppose that i could do this with a virtual machine bur that seems
very heavy weight.

TIA for any clues on how to do this!

dan