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**To**:**Aquatic-Plants at actwin_com****Subject**:**Re: RO recon****From**:**"Roger S. Miller" <rgrmill at rt66_com>**- Date: Mon, 2 Aug 1999 22:00:05 -0600 (MDT)
- In-Reply-To: <199908021948.PAA01755 at actwin_com>

On Mon, 2 Aug 1999, Kevin Zippel wrote: > On 12 June 1999, Roger Miller posted a great note on reconstituting RO > water (copied at the end of this message). In this post, he makes > reference to an earlier post by Neil Frank, Paul Krombholz, and Paul > Sears, which contained similar info on chemical dosing. I can't seem to > find the original post -- perhaps it's under a PMDD instead of an RO > subject line, in which case I'll never find it! Can anyone point me in > the right direction? It's at http://www.thekrib.com/Plants/Fertilizers/dosing.html > One thing about Roger's recreation of the formula > that confuses me (I'm no chemist!) is how those ingredients can generate > a GH of ca. 3d. Using recommendations posted numerous times on this > list, we know that 2 teaspoons of calcium carbonate will raise 13 > gallons by 4d (both KH and GH). Roger's formula requires 6600 mg of > calcium carbonate (6.6g, approx. 1 tsp) for 50 gal. That's 1/2 the > chemical dose for 4x the water, or 1/8 the previously recommended dose, > which would seem to then yield 0.5 d GH. I don't really know the origin of your dosing advise, but in order for 2 tsp of CaCO3 to create 4 dGh in 13 gallons of water it would have to weigh 1.76 grams per teaspoon, which I think is only about a quarter to a third of the actual weight of a teaspoon of powdered CaCO3. By my estimates it would only take something like 1/2 teaspoon of powdered CaCO3 to generate 4 dGH in 13 gallons of water. You may not be a chemist, but you did a pretty good job of catching a couple problems I had with calculating the dose from the calcium tablets. First, the tablets described in Neil's paper contain 600 mg of *calcium*. I treated them as if they contained 600 mg of *calcium carbonate*. To contain 600 mg of calcium the tablets would actually contain 1500 mg of calcium carbonate. Second, I mishandled the calculation of Kh from the tablets. To be clear I'll state this precisely; I will assume the CaCO3 is dissolved in water creating a solution with a high pH and that the solution will be allowed to react with air or with added CO2 until the CO3-- ions are all reacted to bicarbonate (HCO3-) ions and the pH drops to more reasonable numbers (say, below 8.5). My confusion on this point also altered the amount of sodium bicarbonate needed to make 3 dKH. > Granted, there is also > magnesium in the formula (epson salt), which will contribute to GH, but > clearly less than the calcium (as evidenced by thier final > concentrations in mg/l, 4.64 vs. 13.95). So where am I losing it? The magnesium provides about 1 dGH. The calcium should provide 2 dGH to total 3 dGH. > Similarly, I don't see how KH can be ca. 3d. We get 0.5dKH from the > calcium carbonate, plus 2dKH from the sodium bicarbonate (if 1 tsp gives > 4dKH to 13 gallons, as per previous recommendations, then the 2 tsp / 50 > gallons in this recipe should yield 2dKH, yes?). According to Neil's paper, a 1/4 teaspoon of sodium bicarbonate weighs 1.3 grams, so a full teaspoon would weigh 5.2 grams (+/-, I'm sure). 5.2 grams of sodium bicarb would give 3.78 grams of bicarb. In 13 gallons of water that's 76.7 mg/l of bicarb, or 3.5 dKH. Two teaspoons in 50 gallons would give 2*3.5*13/50 = 1.8 dKH. Close. > 2.5dKH is closer to > the predicted 3 than we got with GH, but still short of the mark. Can > anyone put me in touch with the original post, Neil Frank, or an error > in my calculations? Kevin, thanks for giving the recipes the careful review they need. The corrected recipes follow. Chemical dose/ dose/ measurement 100 liters 50 gallons unit epson's salt 3.5 6.5 1/4 teaspoons calcium carbonate 2.5 4.5 600 mg tablet baking soda 2.5 4.5 1/4 teaspoons potassium chloride 1.5 3 1/4 teaspoons The composition (after the pH drops) should be dose/ dose/ measurement 100 liters 50 gallons units calcium 15.0 14.3 mg/l magnesium 4.7 4.6 mg/l sodium 8.9 8.5 mg/l potassium 11.8 12.4 mg/l bicarbonate 69.4 66.0 mg/l sulfate 18.4 18.0 mg/l chloride 10.7 11.3 mg/l general hardness 3.2 3.1 degrees 57.1 55.0 ppm as CaCO3 alkalinity 3.2 3.0 degrees 56.9 54.1 ppm as CaCO3 Na/(Ca+Mg+K) 0.27 0.26 molar ratio total dissolved solids 79.8 78.9 mg/l And of course, all the same instructions and cautions that went with the first draft could be repeated here. One set of comments down. Any other? Roger Miller

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