[billionzz]

I'm trying to make a KH (carbonate hardness) reference solution.

I'll be using baking soda and di water.

What I'm trying to determine is how to prepare the baking soda. It would need to be dry to make the solution accurate.

For example: 
Using 5 liters of di water, if I wanted the reference solution to be 50dKH I would need to add 6.24 grams of baking soda.

But I'm not sure how dry the baking soda should be for this. If you dry it to much it starts to change chemicals composition.

Does anyone know how I should prepare the baking soda or where to find this information?

Thanks,
Bill

[enahs]

30-45 min at 400^oF (204.44^oC) should drive away all the excess water and CO₂ and not initiate any decomposition.

[billionzz]

Thats what I was originally doing heating it to 400 degrees F for 45 minutes then I came across this information at this web site.

http://antoine.frostburg.edu/chem/senese/101/inorganic/faq/carbonate-decomposition.shtml

This site says that at 392 degree's F that the sodium bicarbonate actually changes to sodium carbonate.

"Sodium bicarbonate is even less stable with respect to heating. Solid NaHCO3 begins to lose carbon dioxide and water around 100°C, with complete conversion to sodium carbonate by 200°C:
2 NaHCO3(s) CO2(g) + H2O(g) + Na2CO3(s) ""

So wouldn't that change everything to get the 50dKH in the 5 liters of water you need 6.24 grams of baking soda and at 400 degrees F according to this information it would be sodium carbonate.

I'm not trying to disagree I'm just rying to figure this out.

Thanks,
Bill