I would not let a tracker bar sit in ammonia very much time as ammonia
will etch brass.  An experiment would be a piece of brass bar placed in
an ammonia jar halfway.  Take the brass bar out after an hour and you
will notice that the ammonia will have reduced the size of the part of
the brass bar that was in the ammonia.

I have used lacquer thinner to remove tubing.  It swells the tubing and
makes it slip off the old nipples.  Only takes an hour or so depending
on the type of lacquer thinner.

Don Teach - Shreveport Music Co.
Shreveport, Louisiana