By Anonymous on Wednesday, June 16, 2004 - 07:20 am:

Hello,

I am interested in finding out how to analyse quantitively levels of NaOH in a water sample. I have been looking all over the place, but iam unable to locate any information. If anyone has any ideas please let me know.

Thanks

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By Anonymous on Wednesday, June 16, 2004 - 08:04 am:

Titrate with standardized acid? Or am I missing something?

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By Anonymous on Wednesday, June 16, 2004 - 08:39 am:

AAS for trace levels?

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By Anonymous on Tuesday, June 22, 2004 - 01:59 am:

I am not a trained chemist, and sometimes the simplest of solution for a problem do not appear.

I have been thinking about a conductivity based method, but once again my lack of 'real' chemistry is letting me down.

If you have any ideas regarding this or more information about teh tritration method, i would really appreciate it.

best regards

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By Anonymous on Friday, June 25, 2004 - 05:35 am:

you put an indikator into your NaOH and titrate it with for example HCl with known konzentration
the volume HCl used for setting the NaOH neutral =Konzentration NaOH

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By Russ on Friday, June 25, 2004 - 01:04 pm:

If there are any other bases in your sample solutions (carbonate, bicarbonate, amines, etc.), they could interfere with a hydroxide determination by titration or make picking an indicator difficult.

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By tom jupille on Friday, June 25, 2004 - 04:08 pm:

Depends on what you're trying to do. If you're not a chemist, you have to realize that there is no such thing as "NaOH" in water. What you have is Na+ ions and OH- ions. Ions have no memory -- there is no difference between a Na+ ion that came from dissolving NaOH versus one that came from dissolving NaCl.

With that in mind:

The concentration of OH- ions is easily determined using a pH meter. If you are not a trained chemist, find a good introductory chemistry text and read the section on pH.

The concentration of Na+ ions can be determined in a number of ways:
- ion chromatography
- flame photometry
- ion-selective electrode
(to name just three).

If the *only* source of dissolved material is NaOH added to the water, then you can measure *either* Na+ or OH- and determine the concentration of NaOH dissolved in your water. You could also measure conductivity and calibrate with known concentrations of NaOH (which I assume is what you're suggesting).

Be careful, however: if there are other sources of ions (of any type), then the conductivity measurement will be useless. Likewise, if there are other sources of Na+ or OH-, then those measurements will also give misleading results.