Reference KH for target CO2 calculator (Drop Checkers)

Again, I don't have a drop checker yet, so this is a thought experiment/bounce, and I hope you can find to time to bounce back.

On another forum a superstar made the point that he thinks, at best, he can read the green color of his Drop Checker vs pH charts at +/-.2pH. This sounds about right so let's run with it for a second.

Let's say I have a drop checker with 3dKH (23ppm CO2 target) and its green. It says I have ~15-35ppm CO2.

I have a second drop checker with 6dKH (45ppm CO2 target) and it is green. It says I have ~30-70ppm CO2.

I use both. Now I know I have 30-35ppm CO2.

(With a 4dKH sample, using the .2pH/color margin of error ballpark, you have between 20 and 50ppm CO2. I am using the 6.6 pH/4 dKH/30ppm CO2 in this post. The calc derives from the formulas we all know and love.)

I could build this margin of error into the calc, as I think everyone understands all we're trying to do is build a smaller ballpark for little coin, and the +/- .2pH/color thing is another (good?) guesstimate. What do you think?

By the way, if APC or anyone finds any value to this calculator, you are of course welcome to the source and formulas.

Thanx for all the helpful posts in these forums,

I love the calculator, is it possible to use this to calculate exactly how much to make 4dkh water without diluting any distilled water, unless errors of course.

my contribution:

Our LFS want to rip us off with the sera kit for R200 + in South Africa.

With the help from here i managed to make a Drop Checker using a small glass bottle(Edit: if you want elagance, you can use a nicely shaped lightbulb, just carefully file off the metal part and round the edges of the glass with a dremel and diamond bit.).

Cut to size the screw on cone attachment from an unused Silicone tube. The tube should be silghtly longer than then the bottle(or lightbulb)

i then inserted the cut tube into the bottle, being cone shaped find the correct length that would cause the end of the cone to jam into the opening of the bottle(or lightbulb), once you have the correct length, and inserted the tube, you can seal this with some marine silicone, and let dry for 24hrs.

for indicator solution i managed to distil some water by holding a frying pan style pot with ice in it above another pot that was boiling on the stove. Careful you don't burn with this, if you're a kid you should get M or D to help. What collected under the suspended pot was enough distilled water.

using the tip of a flat jeweler's screw driver i managed to get enough bicarb to make 4DKH water. Simple easy measurement was take two exact containers, add exactly 5ml of the distilled water to both of them. In the one container add 3 drops Kh regent(i used the sera kh kit). this will be the guinea pig jar, using the jewelers screwdriver add a touch of baking soda slowly until it goes green just before it turns blue. Add exactly the same amount used( a scale will really help here) to your second jar.

then add the last drop of kh regent to the first jar turning the solution back to yellow. Now slowly add some bicarb with the jewelers screwdriver, until it just turns blue. Add that same amount of bicarb to the other jar, there you have 4 DKH distilled water. To be sure im sure you could stick a kh test strip in there. now you can just add your ph regent.

hope this helps, if i am wrong anywhere i wouldn't mind suggestions or questions.
I am neither a chemist or specialist, i just tried this ant it seemed to work.

BTW, my ph was 6 in th distilled water, as when i added the pH regent i tested at the same time.

attached is a free CO2 chart that you can print laminate and use, enjoy