I have an issue with a research project. I must determine the concentrations of HNO3 and H2SO4 of samples taken from tanks in an anodizing process. How can I determine the concentrations of both acids through a volumetric analysis? Thanks for your attention.
Hello, Take your mixture perform filtration using glass filter and dilute 1:100 with deionized H2O. An aliquot of 5 mL of diluted solution was taken for sulfate determination.
An aliquot of 3 mL was taken for nitrate determination
Determination of sulfate:
mix 5 ml of sample mixture solution with 50 ml acetone, adjust pH to 2 by adding NaOH (pH is controlled potentiometrically). Add 10-15 drops of indicator solution. Titrate with Pb(NO3)2 solution till first color change.
Prepare a reference sample by adding 5mL standard solution of H2SO4, add 50 mL acetone, adjust pH with NaOH solution, add the indicator and titrate with Pb(NO3)2 standard solution till the first color change.
Determination of nitrates: Take 3 mL sample solution with 5.00 ml FeSO4 solution, add 15mL concentrated H2SO4. Boil the mixture for 3 min, cool and add 20 ml H2O and 1ml Ferroin solution. Titrate with K2Cr2O7 standard solution till color changes from red to blue. Prepare and titrate a blank sample.
Good luck!
Dear Hans Cortés,
If your sample contains only nitric acid and sulfuric acid, how about titrating total acidity with NaOH and then determining sulfate gravimetrically by precipitating BaSO4 with barium chloride solution. Then calculate H2SO4 from BaSO4 calcinated weight. Nitric acid can be calculated by difference from total acidity and acidity from sulfuric acid. That should be the easiest scenario.
Now, if we are talking about a complex mixture that includes other acids and anions, a different method should be used. Nitrates might be determined spectrophotometrically and even by Kjeldahl method. Then you express results as HNO3 and H2SO4, provided pH of the mixture is lower than 7,0.
Of course, if you have access to an ion chromatographer, the task becomes much easier. I'll leave here a reference for this analysis:
https://www.epa.gov/sites/production/files/2015-12/documents/9056a.pdf
Best regards from Costa Rica.
Dear Maynor Alberto Vargas-Vargas here question about titration of HNO3-H2SO4 mixtures?
You are right Karen A. Darbinyan!
The question was about titration methods.
By the way. When you talk about 10-15 drops indicator for lead nitrate titration of sulfate, what indicator are you proposing to use?
Thanks in advance.
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