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How to analyse for sodium nitrate

(-----) 2006

Q. Our shop is looking to run an inhibited caustic etch solution as part of our anodising line. One of the bath constituents is sodium nitrate at 34-49 g/L. Unfortunately the controlling specification nor any of the lab analysis books give any method for determining the sodium nitrate concentration.

Does anyone out there know of any methods and/or where to find such methods documented?


Tony Graf
Plating Shop Employee - Sydney, NSW, Australia


A. Tony,

If your only source of sodium and nitrate in the bath is from this compound then you could measure either one of those using ion chromatography equipment.

Terry Tomt
- Auburn, Washington


A. I guess one of the many commercial test kits for nitrate in well water or drinking water will do the job.
The analysis method would than be something like this:
- make a 1 : 1000 dilution (commercial kits will normally measure in 0 - 100 mg/l range)
- fill a 5 ml test tube
- put test tube in photocell
- read concentration of nitrate or nitrate-N
- convert tot sodium nitrate

Check with the local supplier of these test kits for unwanted side reactions from other components in your application.

Bert Gielen
- Gent, Belgium


A. There is a titrimetric procedure.

A portion of the sample is added to 100 ml of concentrated sulfuric acid. This is then cooled to 0 degrees C. While maintaining this temperature, the mixture (with continuous stirring) is titrated with standard ferrous sulfate solution. A good titer to use is 0.25 N. The ferrous sulfate solution must be standardized vs. a standard solution of nitric acid on the day of the analysis.
The endpoint is a rose color that persists in the acid titration mixture for at least 60 seconds.

You could also run it via nitrate selective electrode, or if you have a UV spectrophotometer, there is a direct reading method. Neither of those things are cheap, but the titration I describe is not easy to do and you might decide to spring for one of them after you do it a few times.

Good luck!

dave wichern
Dave Wichern
Consultant - The Bronx, New York

sidebar December 31, 2014 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Sir
I want to know what is the use of sodium nitrate in anodizing of aluminium. It is used in etching solution or nitric acid solution?

devesh kumar
- delhi india

December 2014

A. Hi Devesh. We appended your inquiry to a thread about the use of sodium nitrate in aluminum etching solutions, which should at least partially answer your question. But you doubtless have a real situation, and for the most helpful answers for it, you'd probably be better off explaining that actual situation than posting in the abstract. Good luck.


Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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