# Need help making calibration solutions



## ElectricHead (Sep 11, 2005)

I need a little help. I wish to make some calibration solutions to check my test kit for accuracy. The solutions I need to make are for KH and GH testing so I can determine Co2 levels. Tested my tap water yesterday and got a reading of GH of 23 degrees and a KH of 16 degrees and I just want to be sure about this.


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## MatPat (Mar 22, 2004)

According to the Fertilator above and Chuck's calculator:

3.5 gm of MgSo4 mixed in 5g of water will give you 18.2ppm of Mg. 1 gm of CaCl mixed in 5g of water will give you 19.08 ppm of Ca. Mix both in 5g of water and you should get about 2dGH (~37ppm).

You wouldneed about 1/4 tsp of Baking soda to raise the KH of 5g by 3dKH (~54ppm).

I have not done either of these tests in a small volume of water, but the KH seems to work for my 15g water changes. Please, let us know if they prove to be accurate.


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## HeyPK (Jan 23, 2004)

To calibrate for GH you would need to have a calcium chloride solution of known concentration. To calibrate for KH, you would use a sodium bicarbonate solution of known concentration. If you have access to laboratory equipment, a balance accurate to two or three places can be used to weigh the dry calcium chloride and sodium bicarbonate out. You would also need deionized or distilled water in which to dissolve these two substances. You might be able to buy standard test solutions from a chemical supply company or a company that makes test equipment. If your tap water is supplied by a water company, the company should be able to supply you with a water analysis that would give you the data you want. If you have your own well, you should be able to get your water analyzed. It might be easier, just to get a CO2 test kit.


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## NE (Dec 10, 2004)

GH does not affect CO2 levels or vice versa normaly.

Kh tests are usually quite accurate, if you like to make more exact measurement double, triple or quadruple the water amount, then the number of drops are parts of degrees instead.

double = 0,5 degrees / drop
triple = 0,33 degrees / drop
quadruple = 0,25 degrees /drop


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## dennis (Mar 1, 2004)

Time to bring this back to life as I need to calibrate my test kits....

From the krib, http://www.thekrib.com/Plants/CO2/hardness-larryfrank.html



> 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
> ...



I want to make a GH test sample using 1 gallon of DI water. According to the Fertilator, adding .5grams CaCl2+2H2O yields 36.1mg/l Ca. Divide 36.1/7.143=5.05 degree GH. Is this correct?

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


> 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
> ...



Unfortunately I do not know how to interperate that. 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 measurment. I have graduated cylinders and syringes so dealing with measurment 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 but would the NaHCO3 have an effect on the GH reading?​


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## dennis (Mar 1, 2004)

Could anyone help me check that math. I am pretty sure it is wrong but I don't know.

I'd really appreciate it


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