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Another DIY 4*dkh Solution

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Ok, so I decided to see if I could come up with another simple and somewhat accurate method to make 4* dkh for my co2 drop checker. This is what I came up with, I verified my results by duplicating the test 3 times and ending up at the same result each time.

Couple primers to start:
- I use my own RO/DI 0 tds water for the solution
- I use a calibrated HM Digital TDS meter
- I use API's Kh test kit
- I have used both Seachems Alkaline Buffer and Baking Soda and both test out the same
- I used everyday CLEAN containers and measuring cups/spoons that are used only for my tanks use and cleaned/rinsed with RO/DI water
- I do have lab testing background and have made very accurate 4* solutions but wanted to come up with another A.S. version for the casual hobbyist.
- No it will not be "laboratory" grade/accuracy but in my experience it is close enough for the casual hobbyist.
- I have been in the hobby for over 20 years but new to the forum

1. Start with 6 cups of 0 TDS water in a clean measuring container
2. Add 1/8 tspn Sodium Bicarbonate to the 6 cups of water and mix
3. Pour out 3 cups of this mix and discard
4. Add back 3 cups of 0 TDS water and mix
5. Pour out 3 cups of this mix and discard
6. Add back 3 cups of 0 TDS water and mix
7. Pour out 1 cup of this mix and discard
8. Add back 1 cup of 0 TDS water and mix
7. Water comes out to +/- 70 ppm TDS and will test @ 4* DKh solution

Any questions or comments welcomed. And if someone has the same basic matierals, I would like to hear if you were able to duplicate my results :)

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That is a very good method, even though I didn't try to check to see if it should be accurate. The good part is that everything is measured in large enough quantities to do accurately, and then it is just dilute, dilute, dilute. Lots of waste, but baking soda is cheap.

May I copy and paste this in the sticky in the fertilizing forum?
 

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RO/DI (reverse osmosis/deionized) water is about the same as distilled water - you probably couldn't detect the difference. Zero TDS (total dissolved solids) is a measure of what is in the water, not a method for achieving that - distilled or RO/DI will very likely be 0 TDS. The goal with making a KH standard solution is to have nothing in it that affects pH except carbonates/bicarbonates and CO2. Distilled or RO/DI would both work, assuming they were properly done. And, if they aren't perfect, the water is still good enough for what we need.
 

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You can use twice as much water in the KH test tube and each drop of the reagent equals 0.5 degrees of KH, making it easier to determine that the KH is 4 and not 3.5 or 4.5 dKH. Of course this means assuming that the test kit reads accurately, and if it is more than a year or so since it was manufactured, it might not do so.
 

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There are instructions for making your own indicator reagent, from bromothymol blue dye, on the internet. It makes no sense to try that if you can buy a good pH test kit that uses that type of reagent, because we use only a few drops at a time. But, I know you can't buy a good pH test kit everywhere in the world.
 
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