DIY KH Keeper reagent

[gbroadbridge]

I think there is an issue with the probe overestimating pH, which cant help having an accurate ph titration. This is maybe because it is only calibrated at pH 4 and 7 and not at pH 10, which means that we do not calibrate the probe within the range of aquarium pH.

The endpoint of a titration to establish Alkalinity is around 4.5pH which is why we calibrate using pH 4 and 7 buffers.

To a certain extent the exact pH is not relevant for this unit as it detect the titration inflection point rather than using an exact pH value as the endpoint.

 

[gbroadbridge]

because probably i have issues in mixing it. my kh is more or less 0.6 dkh lower than any test kit and if it was 0.025N it would match almost 100%

How exactly are you creating the solution?

It is vital to use accurate volumetric measurements if you are diluting from a more concentrated acid.

You cannot use mass (weight) for the dilution.

Also when calibrating the pumps in the kh keeper, keep the same point in mind, i.e. 50ml of seawater does not weigh 50 grams.

In any event, if your measured Alk is within 0.5 dkH of another test, you are within the measurement uncertainty of the tests.

 

[elysics]

I had similar issues thinking it was 0.021 N that i was using because i thought 0.02N overestimated it by 0.2 to 0.6 - after a few months this more concentrated reagent now under estimates KH - maybe there is a drift in measures as the ph probe degrades ?
I had the same issues of measures not matching other tests kits with the branded reagent, and reef factory had not been able to give a better response than asking me to re-calibrate or to offset the measures

I think there is an issue with the probe overestimating pH, which cant help having an accurate ph titration. This is maybe because it is only calibrated at pH 4 and 7 and not at pH 10, which means that we do not calibrate the probe within the range of aquarium pH.

anyway, it seems that we must accept some variability between tests kids and measures and once you move on from these, the kh keeper remains an excellent tool to monitor the stability of your aquarium water

It's not supposed to measure aquarium pH, it is supposed to measure when it has added enough acid that the pH is around 4 or so.

 

[iLMaRiO]

How exactly are you creating the solution?

It is vital to use accurate volumetric measurements if you are diluting from a more concentrated acid.

You cannot use mass (weight) for the dilution.

Also when calibrating the pumps in the kh keeper, keep the same point in mind, i.e. 50ml of seawater does not weigh 50 grams.

In any event, if your measured Alk is within 0.5 dkH of another test, you are within the measurement uncertainty of the tests.

i was using a precision scale
usually they are more accurate than measurement cylinder

what would you use?

 

[gbroadbridge]

i was using a precision scale
usually they are more accurate than measurement cylinder

what would you use?

You cant use a scale and expect accurate results.

I use a 100ml volumetric flask.

 

[Borat]

i was using a precision scale
usually they are more accurate than measurement cylinder

what would you use?

Your problem is not due to measurement precision, you are out by 10% acid volume based on your test. This means 100ml of acid that you dilute +/- 10ml... whatever you use - volumeric or precision scale will have at most 1% error, so precision is not to blame..

 

[iLMaRiO]

Your problem is not due to measurement precision, you are out by 10% acid volume based on your test. This means 100ml of acid that you dilute +/- 10ml... whatever you use - volumeric or precision scale will have at most 1% error, so precision is not to blame..

well, i'm not sure.
current test is 5.86 with my tester, with hanna is 6.8, with tropic marin is 6.6/6.7
I have near 1.00 dkh less than the home test.

i've added a log that show what should be the dkh with a different hcl mole:
mole 0.019 ==> dKh 5.57
mole 0.020 ==> dKh 5.86
mole 0.021 ==> dKh 6.15
mole 0.022 ==> dKh 6.45
mole 0.023 ==> dKh 6.74
mole 0.024 ==> dKh 7.03
mole 0.025 ==> dKh 7.33

With 0.02m dkh is 5.86 (my test), but with 0.023m dkh would be 6.74, nearly equal to the home test.

so, the question is: starting from 0.2N (reef factory), how much extra reagent I have to add to go to 0.023 ?
Is the 10ml extra reagent added as error (or less water than the requirement) enough to move from 0.02N to 0.023N ?

 

[Bent17]

Quick question.. is 100ml of reagent the same as 100g of reagent?

 

[bozo]

Sorry to resurrect this thread.

So I have an option to buy an older model KHG that probably hasnt gone through firmware upgrades.

or buy the newer one and risk it getting locked using DIY reagents.

Is anyone using the KHG pros with DIY reagents successfully?

Thanks