CA measurement in Kalk mix?

Discussion in 'Propagation' started by jdizzle707, Feb 19, 2011.

  1. jdizzle707

    jdizzle707 Guest

    Jun 6, 2009
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    I've been using Kalk mix in my ATO but I've been running a little low in CA so out of curiosity, I thought I'd check the CA concentration in my Kalk mix. I didn't even put 10 drops of the second API solution and it already turned blue. WTH?!? Compared to my tank, I get around 19 drops and my fresh salt mix around 25 drops.

    Isn't the Kalk mix supposed to be super concentrated CA solution?

  2. lattehiatus

    lattehiatus BOD

    Feb 6, 2011
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    The first question that pops into my head is, are you preparing completely saturated kalkwasser, with precipitate settling on the bottom of your container after thorough mixing?

    RHF also states that suspended solids in kalkwasser can cause false readings in calcium tests, but it sounds to me that he's suggesting the solids would cause a false high reading, and not a false low reading. He prefers pH and conductivity as measures of kalkwasser potency.

    "The Degradation of Limewater in Air" by Randy Holmes-Farley:

    "Measuring the potency of limewater can be complicated. Limewater often has suspended particulates in it. These particulates can include both Ca(OH)2 and CaCO3. With certain methods used to measure potency, these solids can become problematic. For example, alkalinity tests typically involve measuring the amount of acid required to lower the pH to about 4.3 At that pH, particulates of both Ca(OH)2 and CaCO3 will dissolve, potentially giving false high readings. Likewise, measuring calcium may suffer a similar fate with many test kits where solids may dissolve and be detected. Other techniques, such as Inductively Coupled Plasma (ICP) used for calcium and impurities will also detect the solids. Filtration can reduce the particulate load, but many of the particulates that form when limewater interacts with carbon dioxide will be smaller than any normal filters (less than 0.1 mm).11

    Two techniques that are largely unaffected by the presence of solids are pH and conductivity. Of the two, pH is much less useful because the change in pH that comes from a small change in potency is hard to properly quantify. Nevertheless, aquarists can monitor the pH of limewater to see if it still retains most of its potency. Instead of comparing to an absolute number, aquarists should compare the pH of the limewater in question to limewater that is known to be saturated (for example, two teaspoons dissolved in a cup of pure fresh water). While exactly how much the pH drops with a drop in potency is complicated due to the presence of CaOH+, as a rough guide a drop of 0.3 pH units is equivalent to a drop of a factor of two in hydroxide concentration (that is, a drop of a factor of two in potency)."

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