Ammonium Bifluoride Analysis

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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 Fotini
H.A.I - Greece

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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

First of two simultaneous responses -- +++++

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 0.1 N 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 speadsheet. The endpoint is at the inflection point of the curve.

Dave Wichern
- The Bronx, New York

Second of two simultaneous responses -- +++++

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

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Q. Need a Titration for Ammonium Bifluoride Casting Etch. We have a requirement for the original build of the tank but we do not have a method for control other than the etch rate? How can we assure our customers that we are maintaining a concentration of 7-9 oz/gal (50# per 100 gal)of Ammonium Bifluoride remainder Nitric Acid 42 Degree Baume'

Stephen Wood
Ozark Mountain - Cuba, Missouri, USA

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A. Stephen,
I had to set up a known standard of the nitric and bifluoride solution, then titrate for both acid-base and bifluoride. Bifluorides are determined using a titration with Thorium Nitrate in Total Ionic Strength Adjustment Buffer. I'll go through my old notes and give you the constants. I know that using a 5 ml sample and 0.1N Thorium Nitrate, I multiplied mls of titre times 0.636 to determine oz/gal NH4HF2.

Randy Fowler
Cleveland, Tennessee, USA

Ammonium Bifluoride

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A. Thorium nitrate titration is a reliable analysis method but...it is radioactive so most labs don't use it for years already.

Sara Michaeli
chemical process supplier
Israel

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

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