DIY KH Keeper reagent

Quatrc · Apr 5, 2023

Hydrochloric acid, volumetric solution 2.0 M (2.0 N) -1 L maybe you can tell me how to mix the proportion?

Dennis Cartier · Apr 5, 2023

Quatrc said:
Hydrochloric acid, volumetric solution 2.0 M (2.0 N) -1 L maybe you can tell me how to mix the proportion?

To get to the needed end result, 0.02N, you would need to dilute it at a 99:1 ratio. So to do it in one step, a 10 ml volume of the acid standard added to a 1L volume, that is already 50% full with RODI, then fill the rest of the 1L volume with RODI, will provide a 0.02N final solution strength.

To do it in 2 steps (may be easier to work with larger volumes). A 100 ml volume of acid standard, added to a 1L volume, that is 50% full with RODI, then fill the rest of the 1L volume with RODI, will provide an intermediate strength of 0.1N. Then you would dilute the 0.1N by combining 250ml of the 0.1N with 1L of RODI, for a total volume of 1250ML at the required 0.02 N strength.

Andrew36 · Apr 15, 2023

What is the best container to use to keep the mixed reagent in?

gbroadbridge · Apr 15, 2023

Andrew36 said:
What is the best container to use to keep the mixed reagent in?

I use PET soda bottles (suitably labelled with warnings)

Quatrc · Apr 25, 2023

Hydrochloric acid, volumetric solution 0.1 N -1 L maybe you can tell me how to mix the proportion?

Dennis Cartier · Apr 25, 2023

Quatrc said:
Hydrochloric acid, volumetric solution 0.1 N -1 L maybe you can tell me how to mix the proportion?

That would be the same as the OEM reagent.

So you would dilute the 0.1N HCL by combining 250ml of the 0.1N HCL with 1L of RODI, for a total volume of 1250ML at the required 0.02 N strength.

Dayvinho · Apr 29, 2023

Big thank you to those who have contributed to this thread, before I order acid, I was hoping to check I am not being an idiot. We are referring to:

Hydrochloric Acid 0.1M (0.1N) Solution

In this thread right?

Dennis Cartier · Apr 29, 2023

Dayvinho said:
Big thank you to those who have contributed to this thread, before I order acid, I was hoping to check I am not being an idiot. We are referring to:

Hydrochloric Acid 0.1M (0.1N) Solution
In this thread right?

Correct

Alex.qld · May 27, 2023

Hello and thank you for this thread, very interesting and useful

I am under the impression that hcl 0.02 n slightly overestimates the kh
note that i dilute it from a chemistry store 0.1n standard solution using precision scales and the findings below are reproducible

with some testing and guessing i found that 0.021 n gives a more accurate reading

Given that i dont know how to do the math i wonder if anyone could help

My findings with the drip method are as follows

For 0.4 with Salifert - that is to obtain a complete change in color - it is a stable purple at 0.42 but adding another drop makes it pinker
with the diy solutions i have
0.36 with 0.21m
0.3. With 0.2 m

this is a correspondence table found in the devices instructions

thanks r2r pros

gbroadbridge · May 28, 2023

Silexa said:
Hello and thank you for this thread, very interesting and useful

I am under the impression that hcl 0.02 n slightly overestimates the kh
note that i dilute it from a chemistry store 0.1n standard solution using precision scales and the findings below are reproducible

with some testing and guessing i found that 0.021 n gives a more accurate reading

Given that i dont know how to do the math i wonder if anyone could help

My findings with the drip method are as follows

For 0.4 with Salifert - that is to obtain a complete change in color - it is a stable purple at 0.42 but adding another drop makes it pinker
with the diy solutions i have
0.36 with 0.21m
0.3. With 0.2 m

this is a correspondence table found in the devices instructions

thanks r2r pros

Kh Keeper uses 0.02N HCl.

When diluting from your standard 0.1N acid, you should be doing so by volume, not by weight.

That could explain the minor error you are experiencing.

The Salifert acid is not 0.02, but is quite close.
Someone calculated it recently in another thread.

Alex.qld · May 28, 2023

Makes sense, thanks

i did not find a way to accurately measure large volumes, that's why i have been using scales.

Dennis Cartier · May 28, 2023

Silexa said:
Makes sense, thanks

i did not find a way to accurately measure large volumes, that's why i have been using scales.

You should look into volumetric flasks. Even the lower accuracy, inexpensive ones, will still be far more accurate than doing it by weight using consumer grade scales.

They come in 1L sizes, but do get expensive and rare in larger sizes.

gbroadbridge · May 28, 2023

Silexa said:
Makes sense, thanks

i did not find a way to accurately measure large volumes, that's why i have been using scales.

I use a 100ml volumetric flask for making one litre of kh keeper reagent.

It's a little tedious, but unless you've actually checked the calibration markings on cheap volumetric flasks you need to use the same one for measuring both the acid and the DI water.

8 x 100 ml DI water + 2 x 100 ml 0.1N HCl.

Doesn't take too long really

Alex.qld · May 28, 2023

I thought doing it by volume would be less precise, but did not take into account that my scale may be the issue and didnt know about volumetric flasks.
I'll get some flasks and do it by volume next time
thanks for the hint
A

iLMaRiO · Jul 12, 2023

can someone please measure the pH of the diluted reagent?

Borat · Jul 12, 2023

Alex.qld said:
I thought doing it by volume would be less precise, but did not take into account that my scale may be the issue and didnt know about volumetric flasks.
I'll get some flasks and do it by volume next time
thanks for the hint
A

If you are to use 100ml volumetric flasks - these are tall and narrow flasks, not just any flask that has 100ml graduations..

Cheers,

B.

iLMaRiO · Oct 11, 2023

Guys, are you 100% sure that kh keeper reagent is 0.02N and not, in example 0.025N ?

gbroadbridge · Oct 11, 2023

iLMaRiO said:
Guys, are you 100% sure that kh keeper reagent is 0.02N and not, in example 0.025N ?

Absolutely 100% sure. Been mixing my own for almost 2 years.

Why do you ask?

iLMaRiO · Oct 11, 2023

gbroadbridge said:
Absolutely 100% sure. Been mixing my own for almost 2 years.

Why do you ask?

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%

Alex.qld · Oct 11, 2023

iLMaRiO said:
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%

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