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post #13 of (permalink) Old 08-27-2010, 03:57 PM
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I would just make it again, if you have the reagents to spare.

If you have access to an analytical scale (which I assume you mean by "laboratory scale"), then you can scale it down from 6 grams to (say) 0.6 grams and make 500 mL of 40 dkH water only.

From there, just take 100 mL of the 40 dkH water and add to 900 mL of DI water to get your 1 L of 4 dkH water.
Thanks for the advice.

I measured it out again. Still coming up with 5 kh. I do get the blue to be pale greenish at four drops, but it does take 5 to seal the deal and be yellow. I guess the arm and hammer is suspect? It is a new box tho, and any added moisture would give me a lesser amount to the mixture, so a lesser concentrated mixture. I checked the scale, and it has been calibrated recently. I carefully measured the water with plastic disposable eye droppers. I checked the TDS in the mixture, and it came out at 74 ppm (which I suppose would be the most accurate way to measure it). Oh, just checked my conversion chart. It should be 71.6 ppm. It is good to write things out sometime isn’t it? That will be a good way to dial it in…

The thing is 5 kh is 89.5 ppm. So, I suspect the integrity of the API dropper test (drop size could vary). The room in my lab (not a chemistry lab) that I test in is very well lit with fluorescents, and I do it on white paper for color fidelity. The instructions say the solution should be bright yellow (not pale green). I guess I would have to calibrate my TDS know for sure, what’s going on.

Thanks again
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