TDS-Conductivity relationship for nitric acid

[Ikkyu]

Hello everybody,

I read about TDS and conductivity in http://www.reefkeeping.com/issues/2004-04/rhf/feature/index.php, and thought some of you could have the answer to my questions about TDS.

I am trying to measure TDS in a 2% HNO3 dillution (it has several dissolved salts that I must determine by mass spectrometry), but I get a value far too high from what I expected: 7%. The relationship we've been using so far, between conductivity and TDS is:

TDS(%)=0.068*X(mS/cm)

where X(mS/cm) is conductivity in miliSiemens per centimeter. This relation is valid for KCl in water, but what about salts in HNO3?? Is the relation still valid??? Thank you.

Ikkyu

 

[Randy Holmes-Farley]

This relation is valid for KCl in water, but what about salts in HNO3?? Is the relation still valid???[?B]

No. Nitric acid will have substantial conductivity in the absence of any KCl.

Adding a specified amount of KCl to nitric acid will boost conductivity, and the amount it boosts is will be similar to (but not exactly the same as) the amount it boosts pure water, AS LONG AS both the KCl and the nitric acid are at fairly low concentrations.