If I remember correctly, baking sodium bicarbonate starts converting it to sodium carbonate and carbon dioxide, as well as driving off the water. That makes it virtually impossible to know how much carbonate is being added per gram. It was learning about this that caused me to give up making my own KH solutions.

Vaughn I can bring some Reference KH also to this month's meeting.



Regards,
Tom Barr

Here's a question no one ever seems to ask, what's the pH of neutral pH water at 35C?

Think it's 7.00?

You would be wrong.

The neutral point of pH is not always 7.0. It depends upon what temperature you measure the pH of the sample. For example, at 35oC, neutral pH is 6.84. And also the method used.

The pH can be measured either colorimetrically or electronically. The colorimetric method is much cheaper and sometimes faster, but suffers from interferences due to color, turbidity, salinity, colloidal matter, various oxidants and reductants. Indicator/color reagents are, themselves, subject to change with time and can even change the pH of poorly buffered samples. For this reason, colorimetric methods are suitable only for rough estimation. The glass electrode probe w/temperature compensation is the standard technique.

So what about the scale at which we measure pH/KH?

We can actually measure the CO2 level inside the plant itself as well as O2.
Not just the water.

We can also measure the regions near the plant in say a high vs a no or slow flow area, how?

Using the micro probes.

Dissolved Oxygen Products

Yea, they cost a bit
However, I've made probes(especially when you need 40 of them!).
I am going to be working on some for submersed plants at the microscale.

Some items that are not cheap, but discusses how we can use optical methods to measure CO2:

John Morris Scientific :: Service plus Solutions :: Instrumentation

My O2 meter uses this instead of the membrane.

I'd personally like to get away from KH references and pH, I'd rather try these methods

However, at tiny scales, the ability for the KH/pH probes to function over short time scales is greatly enhanced.


As you can see, I'm a few steps ahead here, but have been using these types of techniques and methods to get at some of the more prevalent questions I have about aquatic plants.

This trickles downs to the hobbyist, and even more so because I'm not locked away in some lab keeping it to my self and nerdy researchers

I think it would be best to be able to use the pH/KH pH probe micro scale method, for DIY projects etc and perhaps a wise company will make them. Milkwaukee and American Marine expressed interested, but......I bet they will never make them.
I'm also not sure how well they will function or with respect to time.

So..........sometimes............if you want to know and an answer a question, make something etc, you have to do it yourself.


Regards,
Tom Barr

Some flat tip model and more micro's:

Bit $$
U.S. Price List

and a relative cheap flat tip:

Growers Field Checker Direct Sample pH Tester - 50k -

these folks have a few items of use.

pH electrodes products online index - shelfscientific.com

Simply adding a tiny balloons of KH ref solution w.membrane over the tips will work well, they are delicate, so I've been considering just adding them each time I want to make a measurement somewhere, and not just in the tank in general, you can measure near the reactor and in low flow areas with high lights, you will see large CO2 differences.

You can use about 200-500ul of KH ref solution and make the membranes about the size of BB or a tad larger, maybe about 1/2 the the size of a pea.
Place a drop on the membrane, then wrap carefully around the tip of the pH micr probe.

I usually add the O ring first on the pH probe, then roll it down and over to get a good snug fit and try to remove any air bubbles. I've torn more membranes than I care to admit But with practice, you can do it.

Flat tip pH probes should get close as well.

I'd give the standard pH probes with glass bulbs etc and say 1-2mls of KH solution at least 15-30 minutes. Wait till the pH reading stabilizes.
also, see how fast it can respoind to a tank that you just changes the CO2 inflow rate(say 2x more suddenly, then see how long the it takes to stabilize at the new lower pH).

Regards,
Tom Barr