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/water...tober/1428.pdf



Regards,
Tom Barr