As a large supplier of tin strip chemistry I can tell you that your nitric
chemistry should hold about 150g/l tin, 20g/l iron, and 10g/l of copper. The
chemistry should not contain any chelaters and most large customers simply
bleed this into their non chelated metal bearing waste streams. A tin strip
consumption of 1 drum a day would mean that you would only need to feed 2
gallons an hour to your waste stream. This dilution is usually helpful. 

I would check the level of copper in the spent chemistry and if it is over
12g/l you are etching excessive amounts of copper. The etch rate on a broken
in bath should be only 10 - 15 millionths/ minute.

Regards,
Chris McGary
Dexter Electronic Materials

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