Originally Posted by Ken Garlock
David, I would not be concerned.
Plumbers use acid core solder, and acid based flux all the time. Consider that the flux is just there to clean the surface of the copper so that the solder flows nicely and makes a good connection to the copper. By the time you get the pipe up to temp with your propane torch, you will never know that the flux was ever there, as it will be totally boiled way.
When I did my copper air lines, I bought a bottle of Ruby Fluid flux from McMaster & Carr. It is a non-acid based flux. I bought it because it was cheap....