Making Standard KH solutions

Several sources I've looked at suggest quite different standards as well.
I arrived at the 4.99 grams from the reef side (namely ReefCentral folks)which tend to be anal about such things.

Using something other than baking soda(heat CO2/water issues) might be tougher to dissolve, but would not entail as much errors in other areas.
I asked Greg Morin and there's some discussion on various reef forums.

I'm looking at other standard base chemicals to get the bicarb HCO3 other than baking soda for a KH solution.

I have not gotten around to it, nor the pH membrane probe test either, but in due time I will.

Regards,
Tom Barr

 

I totally agree, this is where SeaChem could sell ref solutions and make some $.
I think if we all bother Greg Morin, he might.

Regards,
Tom Barr

 

Due to H2O and heating losses of CO2 with baking soda, I think side stepping baking soda all together may be wiser.

All that's needed is something can be dissolved and has KH.

Regards,
Tom Barr

 

But that method is only as good as the non calibrated test kit

I do not trust test kits, we need to have a simple standard reference solution, not a test kit.

That's the idea behind the reference KH solution after all

Lamotte's test kit is good to 4.4ppm.
I'm not sure of the accuracy though.
Better than most test kits though.

Please read this link, it will help you:

Reference.com/Encyclopedia/Alkalinity

Now go back and read it

Reference.com/Encyclopedia/Carbonate alkalinity

Randy suggest the Hach Test kit might be best since the measure is sharper than others.

Chemistry and the Aquarium - Randy Holmes-Farley

Please read all of this.
It will answer 99% of your questions.

And it will raise many more in their place

Note, doing a pH endpoint tritration, you can use a pH probe/meter to measure the exact end point where all the KH is consumed by the strong acid.

Sodium carbonate or potassium carbonate etc will work and have less volitility than baking soda.

Here's an interesting paper of low KH water measurements:
http://www.wrc.org.za/archives/watersa%20archive/2001/October/1428.pdf



Regards,
Tom Barr

 

Now look, there are many ways to define alkalinity, but a darn good test kit/method should be in place if you plan on doing this right.

Folks from years past screwed up NO3 and PO4 using cheapo test kits and poor assumption. About 11 years Steve Dixon got fed up and adopted the Lamotte abnd Hach line to get around this issue. I followed suit and then questioned whether the Lamott and Hach kits where accurate as well.

Here's a digital Alk test:

Hach - Alkalinity Test Kit, Model AL-DT, Digital Titrator, 10-4000 mg/L, 100 tests

Here'a a cheaper HACH test kit:

Hach - Alkalinity Test Kit, Model AL-AP, Drop Count Titration, 100 tests

Here's the Lamotte:
Alkalinity Test Kit

Look, don't monkey around all hodge podge here, do it right and then you can feel better about it.

The Chemistry Section: Alkalinity

And for the UK folks: Hanna Instruments HI-3811 Alkalinity Test Kit

1ppm ain't bad

Hanna makes a one for the USA yanks as well.

Regards,
Tom Barr

 

Okay, I now have NIST referenced alkalinity solutions. They are high concentration, 25,000ppm as CaCO3 measurment from Na2CO3 and 10mls. So one will make 3.49944 liters of 4 KH solution: 71.44ppm.

Since the accuracy is high at high concentrations, the dilution downstream errors will be very low.

I have a nice Volumetric flask as well and some smaller ones and pipettes that are accurate to 0.01ml for the topping off part or I could snatch a micropipette from work.

But I do not think I need that mucn accuracy, this will get me well below the 0.1ppm range and that will not influence CO2 much(much less than 1ppm).

Greg Watson might sell it also. We shall see.
Given they are small etc and make a lot, they would be well worth it since most folks will have to buy a scale, and deal with the mixing and other unverifiable issues.

This way it's a lab grade solution you dilute.
Vaugh, you want 1 liter of certified 4KH solution?


Regards,
Tom Barr

 

I suggested using Sodium Carbonate to resolve the baking soda H2O and CO2 thing/issue.

I also have a lab verified reference sample at very high concentration, thus making shipping easier, as well as more accuracy when dilutions are done.
This provides higher confidence levels and it's easy, the solutions are pre made, all you do is dilute accurately with a flask with DI water.

The best test method would involve tritration pH meter end point and a digital tritrator like the HACH.

One thing is clear, test kits vary in this hobby, as do the dosing calculators for KH measurements. The range of accuracy is fairly wide and in most general cases, this is not an issue.

But we should all try hard to maintain a standard that's something we have confidence in. All these calculators have assumptions built into them.

You'll note Rnady and others do the chemistry and seldom rely on calculators. I am pre calculator in my area, so I do it the old fashion method as does Paul Sears or Randy at RC.

But for accurate critical measure of CO2, it is important.

For the drop checker method, having a lab verified reference solution that you can count on truly, is a nice option for a few $. I think it'll be about 10$+ shipping or so and 3.5 liters ought to last a few years and allow you to send all the KH ref solution you want to the friends etc

From there, a pH probe will be the thing that's the issue but ref solutions and their accuracy is easier to check for pH than KH.

I think this discussion is good as it outlines the issues with KH, it's measure, the web's various opposing measures/dosing calculators, different measurements etc, and methods available, test kit issues as well as a lab verified reference stock solution that is now available.

Before the myths start to amplify on the web, some definitive resolution should be made.

It seems that for lower Ref accuracy, the baking soda is fine.
For higher confidence/accuracy levels, go a lab grade vertified ref sample, they are relatively cheap, get a Volumetric flask((10$ or so for a 500ml) and you'll have plenty for years.

This will help understand and variation we see and give a new group of folks some back ground on the other types of alkalinity beside the carbonate type.

The system is more complex than some might assume on the Krib or various web sites.

And each step, going after such issues critically and in great detail, helps to provide a "closer to the truth" approach.

We may never arrive at the truth for most things, but we will know more about the issue and be better able to use it to help us in the hobby/life. I'd prefer that route versus mere belief
That choice is clear, at least to me.

Regards,
Tom Barr