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Determination of HNO3 in degreasing solution containing H2SO4

I want to ask how to determine the HNO3 in degreasing solution for aluminium finishing

Jaja Ija
aluminium manufacturing employee - Klang, Selangor, Malaysia
May 25, 2011

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Pretty vague question, and since I'm batting below the Mendoza line on this board of late, I have to ask, why you are using a combination of 2 acids for degreasing on aluminum? It's a lot more common, I believe, to be using a mild alkaline solution (heated) with surfactants.

Sorry, I can't help with your titration question, but was very curious as to the solution you are using to degrease aluminum.

Am I the only one that's never heard of this practice? Seems to me that it wouldn't be very effective.

Marc Green
anodizer - Boise, Idaho
First of two simultaneous responses -- May 27, 2011

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It doesn't sound like a "degreasing" chemistry to me, but putting that aside and assuming that you only have those two acids in the mixture and that you require a non-instrumental method, you would need to determine sulfuric acid via a gravimetric analysis of sulphate. Then total acid by simple pH titration. From there it is just a matter of doing the math to get reportable results as nitric acid and sulfuric acid. Everything you need to know can be found in your quantitative chemical analysis textbook.

For instrumental methods, ion chromatography is straight forward for separating nitrate and sulphate. Also, an appropriate autotitrator would be able to distinguish the two by their relative inflection points.

If you don't have the knowledge or the time to develop the method, you would be better off buying a proprietary chemistry solution. That way, you would just simply follow their written analytical procedure step by step.

Jon Barrows, MSF, EHSSC
GOAD Company

Independence, Missouri

Second of two simultaneous responses -- May 27, 2011