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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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Titration end point for Nitric Acid concentration
What is the correct pH to titrate to when determining the concentration of Nitric Acid ? Also which indicator is correct - Bromothymol Blue, methyl orange ⇦ this on eBay or Amazon [affil links] or methyl red ⇦ this on eBay & Amazon [affil links] ?
A. Hanesmanufacturing - ammonium nitrate, nitric acid - Brockville, Ontario, Canada
2003
2003
The indicator that is best may depend on what impurities may be in your nitric acid. If, for instance, you are certifying technical grade nitric acid to federal standard A-A-59105 (O-N-350), then methyl red ⇦ this on eBay & Amazon [affil links] is used (pH=6.3). For an acid bath that may contain metallic impurities, it may be more appropriate to use methyl orange ⇦ this on eBay or Amazon [affil links] with a lower endpoint at 4.4. Bromothymol Blue has an endpoint at 7.6. In a clean solution, you will find that it makes very little difference which one you chose as the pH change is very rapid near the equivalence point of the titration.
Jon Barrows, MSF, EHSSC
GOAD Company
Independence, Missouri
You can check yourself with PH meter and then You will see a sudden pH change when titrate and I think M.O is correct.
SE DO JANG- KOREA
2003
In simple language, the lower pH indicator will work better or you may be titrating nickel or iron or ? as well as the nitric.
James Watts- Navarre, Florida
2003
What is the correct pH to titrate to when determining the concentration of Nitric Acid ? Also which indicator is correct - Bromothymol Blue, methyl orange ⇦ this on eBay or Amazon [affil links] or ⇦ this on eBay & Amazon [affil links] ?
A.R. HanesManufacturer - Nitric Acid - Brockville, Ontario, Canada
2003
If this is virgin Nitric acid, it makes virtually no difference which indicators you use. Yes, that is the truth. It would take 2-3 pages to explain why. Now if you have dissolved metal in it, you want to use an end point pH that is below where the metal precipitates out as a hydroxide. Go to a college chemistry department and ask them to titrate a sample for you using a pH meter. Record and graph the pH vs every 0.5 mL of titrant. Allow about a minute for each to stabilize before adding the next increment. You will find that the pH rise is very shallow to a point that it starts rising faster. At this time switch to 0.1 mL additions.At one point the line will go nearly vertical and then fairly rapidly return to a shallow rise. The vertical point would be the ideal pH, but if you look at the difference in titrant volume from the low pH to the high pH, you will find that it is very small.
If you do a titration in your lab and are doing it correctly, one with each indicator, you will find that there is probably 0.1 mL of titrant difference from the low to the high.
James Watts- Navarre, Florida
2003
Your question has been answered thoroughly and am puzzled why you have asked it again. I noticed this time that you are manufacturing nitric acid, so you are not analyzing contaminated solutions or plating baths. In Canada there must be some standard that your customers are asking you to certify the product to. For the US a common standard is A-A-59105 (formerly O-N-350) for Technical Grade Nitric Acid. The standard itself says to titrate with ⇦ this on eBay & Amazon [affil links] and gives the necessary calculation. If there is some other standard you should meet, then look it up. If not, it is reasonable to use the standard I mentioned as a template that tells you exactly what to do. It is available online at http://stinet.dtic.mil/
Jon Barrows, MSF, EHSSC
GOAD Company
Independence, Missouri
2003
If I have Titrate acid nitric in a solution of copper nitrate ⇦ this on eBay or Amazon [affil links] , what is the adequate titrating solution and indicator?
Juan Vera- Lima
2006
Good day. we are using aqueous nitric acid for our metal etching, and the monitoring we make is only based on pH. is there a titration method to determine concentration the of HNO3 in our etching tank? it will help us very much if a procedure could be provided. Thank you.
Reyna Soriapainting - Cebu City, Philippines
2007
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