Harold & GSP,
Right on, the heating process should be for de-chlorinating and de-noxing.
JoeHast, I'm sure Harold would say "Incineration, Double Incineration" LOL Might be the sulphuric is still in your cell mud causeing issues.
Arthur, if your process works for you in a certain refining process, more power to ya. Like LazerSteve suggests though, become very familiar with stannous chloride tests, and do it with all your washes and solutions. Keeping certain pm scraps seperate, and recording values from these pm scraps would be a great help for future refining processes.
One thing I would like to remind you of though, adding iron and copper is the long way around getting your values. It is usually considered the panic button in refining as you are trying to eliminate these elements from your gold. Then useing nitric again to redissolve the precipitant is ok, however, I wonder how much copper comes down with your gold.
May I ask what materials you are refining, It escapes me at the moment.
Good Luck,
Nick