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#### Left C

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Hi guys

I have two of the Red Sea CO2 indicators and I used billionzz's instructions for making KH reference solutions. It was quick and easy. This tells you how to make a 4 dKH solution and a 5 dKH solution.

"To make a KH standard using baking soda you would need the following:

distilled water
baking soda (new and unopened would be best)
.01 gram scale (a calibration weight)

1. Measure 3000 ml of distilled water using the 500 ml graduated cylinder and put it in a clean container. The container could be an empty 1 gallon distilled water bottle. (I found it easier to use 3000 ml, instead of the often suggested 5000 ml because you can make your standard with 1 gallon of distilled water instead of having to have a larger container or multiple containers)

-Place the cylinder on a flat surface.
-Make sure your eye is on a level plane with the of the meniscus.
-The meniscus is the half-moon curve formed at the surface of liquid.
-Water should be read from the bottom of the meniscus

2. Weigh 3.60 grams of baking soda, add it to the 3000 ml of distilled water and mix well, this will make a 40 dKH / KH standard.

3. Pour 450 ml of distilled water into the 500 ml graduated cylinder.

4. Pour 50 ml of the 40 dKH standard into the 50 ml graduated cylinder

5. Pour the 50 ml of 40 dKH standard into the 500 ml graduated cylinder and mix well, this will give you 500 ml of a 4 dKH standard.

6. If you want a 5 dKH standard instead of a 4 dKH - change step 3 from 450 ml to 400 ml and you will end up with 450 ml of a 5 dKH standard."

#### Left C

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Hi Iroc

If you have the equipment to make the solutions, it's really easy to do. If you don't have the equipment, buying it already made is fine.

#### Left C

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It's probably much easier to make a gallon of 4dKH water with small pinches of baking soda, as long as you have source water below 4dKH and trial and 'error' doesn't use up all your KH reagent, then put some in the DC. I think a couple pinches or so will bring a gallon of 0 TDS RO/DI to about 4dKH...
Hi Jaidexl

You're right, it only takes a very tiny amount of baking soda to make a solution. I have over ½ gallon of 40 dKH water left over. That's probably a lifetime's worth. But, you really need to use pure water like DI/RO/De-Io to avoid contamination and false results.

I like your Avatar. "The Creature from the Black Lagoon" is one of my favorite movies. Did you see the original 3D version?

#### Left C

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The keys to making a known reference solution are using pure ingredients and that they are weighed and measured in precise amounts so that you don't have to depend on the reliability and accuracy of a test kit. You know what you made is correct.

#### Left C

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....No, I haven't seen the 3D version ,just black and white on TV a loooong time ago, lol. I wish I could see it though, I haven't ever seen anything in 3D, isn't that sad?
I forgot to mention this about the movie and your Avatar. Did you know that the lady on board the boat that "The Creature" kidnapped was in a Playboy magazine before she made the movie?

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