# [APD] Calibraiting GH and kH test kits

```Hi all,

I am trying to calibrate my Aquarium \\Pharm Gh and kH test kits.  I
have found some info in the web and wonder if I am extrapolating the
math correctly from it.  Any help would be greatly appreciated!  Most of
the info have been able to find on the web deals with rough adjustments
of GH/kH using teaspoons of this or that.  Definitely not accurate
enough for these purposes.  Also, I have seen some info referred to in
moles(M) but I am not very familiar with that.

From the krib, http://www.thekrib.com/Plants/CO2/ha...arryfrank.html
Regarding GH

Quote:
By definition, 1dGH = 10 mg/liter CaO
Atomic Weight Ca = 40, O = 16, CaO = 56
So 10 mg/liter CaO contains 40/56 *10 = 7.143 mg/liter of Ca
By definition ppm Ca is not for elemental calcium but for ppm CaCO3.
Atomic weight CaCO3 = 100
So 7.143 mg/liter of elemental Ca would be expressed as 100/40 * 7.143 =
17.8575 mg/liter(ppm)CaCO3.
1dGH = 17.86 ppm CaCO3 and 7.143 ppm Ca2+.[/quote]

Ok, so say I want to make a GH test sample using 1 gallon of DI water.
According to the Fertilator (www.aquaticplantcentral.com), adding
.5grams CaCl2+2H2O to said gallon of DI yields 36.1mg/l Ca. Divide
36.1/7.143=5.05 degree GH. Is this correct?  Do I need to convert back
to CaCo3 equivilant or something?

Now regarding kH,

quote also from the krib:
Using baking soda, NaHCO3, to adjust kH:
Info below from the same source as above:

Quote:
1dKH = 21.8 ppm HCO3
How to use these conversion factors:
If you have alkalinity in ppm or hardness in ppm divide by 17.86 to get
degrees.
If you want to raise the alkalinity by 1dKH using CaCO3: use 17.86 mg CaCO3

If you want to raise the alkalinity by 1dKH using NaHCO3:
mw Na = 23
mw HCO3= 61
mw NaHCO3= 84
1dKH= 21.8 ppm HCO3
21.8 *84/61=30 mg/liter of NaHCO3
using molarity:
0.358 mMoles * 84(mwNaHCO3) = 30 mg/liter of NaHCO3
[/quote]

Unfortunately I do not know how to interprate that. I am not sure how to
dose 30ml/l of NaHCO3.  Is that simply referring to the HCO3 part of NaHCO3?

I would like to add NaHCO3 to 1 gallon of DI to make my test solution.
If necessary I can make the gallon with a high kH then dilute that
sample as necessary for easy measurement. I have graduated cylinders and
syringes so dealing with measurement accurately is easy enough. I also
have a gram scale with a 0.1 readout.

Would it be possible to use the same gallon of DI for both tests? The
CaCl2+2H2O should not affect the kH and the NaHCO3 should not effect the

I don't want to use CaCO3 for both solubility issues but mainly because
I would like to be able to target a specific concentration for the test.
Using one compound for both hardness would probably give an odd