Testing limewater saturation?

[kevin gu3]

What is the best way to tell if the limewater from my kalk reactor is fully saturated?

I have a pH meter and I know the pH should be somewhere around 12.5. I can also do an alkalinity test and I know the alk should be somewhere around 40.8 meq/l.

Which is the better test? pH is easier, does anyone know if it goes up linearly with increased kalk saturation, or does it pop up and plateau out way before saturation is reached?

 

[Randy Holmes-Farley]

Conductivity is best. I show that in this article:

The Degradation of Limewater (Kalkwasser) in Air
http://reefkeeping.com/issues/2003-05/rhf/feature/index.htm


pH can be used with more uncertainty, and I discuss how in this thread:

http://www.reefcentral.com/forums/showthread.php?s=&threadid=779417

Alkalinity is also a fine way, but it takes a lot of titrant. For an alkalinity test, it must be totally clear limewater, or else the solids will dissolve during the test and give a false high reading. That is not a concern with the other methods.

 

[kevin gu3]

Thanks Randy!

I have a TDS meter but not a conductivity meter. I'm guessing it works on the same principle. Can I use it to test the TDS in a saturated standard and compare that to a reading of the reactor's output?

 

[Randy Holmes-Farley]

If it reads high enough you can, but many TDS meters do not read up to 11 mS/cm, which is more than 5,000 ppm TDS.