Reference solution for KH

[Galeno rocha]

Does any one have a proven recipe for a DIY reference solution for carbonate hardness? I have grown suspicious of my test kits, since they are showing very discordant results.

 

[Randy Holmes-Farley Verified Community Expert]

You can DIY alk test, or DIY standard.

We mention both here:

Alkalinity standard solution diy?

Hello. I have an issue, my 3 alkalinity tests (Red Sea, Salifert and api) ALL have different readings on the same aquarium. Does anyone know how to make a standard solution so I can figure out which is most accurate? Thanks

www.reef2reef.com

 

[AquaPhilNJ]

There is reference solution you can purchase as well Fauna Marin Multi reference solution.

 

[Galeno rocha]

Thanks! So I could buy the one liter solution of NaOH 0,01N, pull 10 mL and add 30 mL of RODI water in order to make a 7 dKH standard solution. Is that right?

 

[JimWelsh]

0.01 * 10 / (10 + 30) * 2.8 * 1000 = 7, so yes.

 

[biom]

Thanks! So I could buy the one liter solution of NaOH 0,01N, pull 10 mL and add 30 mL of RODI water in order to make a 7 dKH standard solution. Is that right?

yes, but be sure you are using lab grade volumetric flask to measure 30 and 10 ml and distilled water if you want real standard solution

 

[Randy Holmes-Farley Verified Community Expert]

Thanks! So I could buy the one liter solution of NaOH 0,01N, pull 10 mL and add 30 mL of RODI water in order to make a 7 dKH standard solution. Is that right?

FWIW, I would not assume such a standard will work with a device like the Hanna. I'd also warn that the color change might be different than usual since the pH will be different at the equivalence point. The exact equivalence point will be pH 7, and another drop will send the pH way down. That will very rapidly go past the normal endpoint in the low to mid 4's (which is good since you will trigger the color change), but it may go past it so fast that you may see different colors than usual.