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Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Ammonium Bifluoride Analysis
2005
Q. I have to analyze a Pickling solution which consists of
1. HNO3 (Nitric Acid ) 53% :690-710 g/l
2. CRO3 (Chromic Acid ) :10-20 g/l
3. NH4HF2 (Ammonium Hydrogen Bifluoride):40-50 g/l.
I used iodometric method to determine the concentration of Chromic Acid and I saw that it works very good.
But I have not found the appropriate methods for the determination of concentration of Nitric Acid and Ammonium Hydrogen bifluoride. I would really appreciate if you could suggest me any method for Determination of Nitric Acid and Ammonium Hydrogen bifluoride in above solution.
Thanking in advance
Kiriakou FotiniH.A.I - Greece
May 25, 2020
A. Chromic acid is determined by iodometric titration as you did, titration with sodium hydroxide to get total acidity. The volume consumed of sodium hydroxide is equivalent to Chromic, Nitric and ammonium bifluoride let it be V1.
Add barium chloride to the mixture this will precipitate fluoride as barium fluoride after filtration and titration again with sodium hydroxide the volume consumed of sodium hydroxide is equivalent to Chromic acid and nitric acid let it be =V2 you can get the volume of sodium hydroxide equivalent to Chromic acid as if you titrate Chromic acid alone with sodium hydroxide, let it be V3
then
V1=Nitric+Chromic+ammonium bifluoride
V2=Nitric+Chromic
V3=Chromic
For example chromic=20%
then 20=v3*100*F chromic*F NaOH weight of sample
Then we can find v3 and substitute for it to get v1&v2
- Cairo @Egypt
Multiple threads merged: please forgive chronology errors :-)
Q. I am looking for an analytical procedure for analyzing ammonium bifluoride in Nitric Acid+Sulfuric Acid+H20 Mixture. Does anybody have any idea? HELP!
Bob Rudes- Santa Clara, California, USA
2005
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2005 A. There are several alternatives: 1) Thorium nitrate titration for fluoride + titration with NaOH for total acidity. I've never done one of these, details are available in the analysis section of the "Metal Finishing Guidebook and Directory". 2) Determination of fluoride via ion selective electrode directly. I would make up 3 - 4 known NH4F.HF standards in a matrix like that which is usually found in the bath, and calculate the concentration in the process solution by comparison with the standard curve. 3) Determination of fluoride via titration with 0.1N lanthanum nitrate, with endpoint detection by ion selective probe. This would be the most accurate method. Use a 5 ml sample, add about 30 ml of water and about 10 g of sodium acetate, and titrate, recording the mV reading vs the ml titrated. Plot the data, either manually or using a spreadsheet. The endpoint is at the inflection point of the curve.  Dave Wichern Consultant - The Bronx, New York A. It can be done with a selective ion electrode method or with a cerium titrant (which is mildly radioactive). Review a lot of the previous posts to this letters section for more information. James Watts- Navarre, Florida 2005 |
October 10, 2012
Q. I am looking for an analytical procedure for analyzing Ammonium Bifluoride in NH3 + DIW + HF = NH4F. Does anybody have any idea? HELP!
Minsu Kim- Cheoin-Gu, Yangji-Myeon, Jubuk-Ri, Korea
Q. Chimex LTD. has on their website some mixtures of etching (matting) solutions. I am particularly interested in their mixture of 75 grams of Ammonium Bi-fluoride, 75 grams Barium sulphate and 100 ml of water. My question is:
Is this an aggressive mixture and if so can it be buffered by adding more Barium sulphate? Thanks.
- lexington, Massachusetts USA
December 19, 2017
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Ed. note: Some other highly applicable threads:
- Topic 5912 "Analysis of nitric-hydrofluoric aluminum etching mixture"
- Topic 54154 "Thorium nitrate or alternate analysis method for fluoride"
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