I need to monitor a nitric dip tank that is being used for passivation
of stainless steel parts.  I have been told a conductivity analyzer is
typically used for this.  I am concerned that dissolved iron from the
passivation process will have great enough influence on the
conductivity of the solution that I cannot therefore use conductivity
to measure the solution to maintain a concentration of 20-40% nitric
acid by volume.
How much iron can be dissolved in a bath of 20% nitric and what at
what magnitude will it affect conductivity?