Summary for nitric strike tank test Discussion
Nitric strike tank test questions centered on replacing a failed pH meter with indicator-based titration for a tank running about 45-50% nitric acid. Noel Yang asked whether thymol blue, with a red-to-yellow transition around pH 1.2-2.8, would be suitable. James Watts replied that thymol blue would work, but said an indicator changing around pH 4 would be a more normal choice. He suggested experimenting with methyl orange and methyl red as cheap, functional options. Watts also recommended using 0.5 N sodium hydroxide instead of 1.0 N, explaining that the weaker base is less likely to precipitate metals from a locally high pH during titration. For mixing, he said a mixer with a Teflon spin bar is easier than swirling an Erlenmeyer flask and worth the extra cost.
Q. I work for a metal finishing shop and have a little problem. Our pH meter has had a heart attack. I am now in a process of turning my tank titration testing procedures from using the pH meter to using indicators. I have done a pretty good job until I ran into the testing of our Nitric Strike tank; tank containing ~45-50% nitric acid concentration. I have tried consulting our books and have not been able to find a titration method that utilizes an indicating solution that has the appropriate visual transition. Should I use Thymol Blue, an indicator with visual transition of 1.2 – 2.8 from red to yellow? If you have any ideas, I am more than willing to listen to them.
Thanks,
Noel Yang
plating shop – Oldsmar, Florida, USA
2004
A. That will work, but one that changed color around a pH of 4 would be a more normal choice. Experiment with methyl orange
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and with methyl red
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. Cheap and functional. I preferred 0.5 N sodium hydroxide
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over 1.0N because it is weaker and does not tend to precipitate out any metals because of a locally high pH. A mixer with a teflon spin bar works a lot easier than swirling with an erlenmeyer Flask. It is worth the extra few bucks in the long run.
James Watts
– Navarre, Florida
2004