Salifert calcium instructions have changed

Discussion in 'Reef Chemistry by Randy Holmes-Farley' started by saltyhog, Nov 13, 2017.

  1. saltyhog

    saltyhog Valuable Member R2R Supporter Reef Squad Leader R2R Excellence Award Partner Member 2019

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    Just a heads up. If you use Salifert for calcium and recently bought a new kit, the instructions have changed. The second reagent that was 8 drops is now 10 drops. I actually did several tests before I caught the change. It made very little difference in my results as best as I could tell.
     
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  2. Hitman

    Hitman SPS Addictions are real!!! R2R Supporter R2R Excellence Award Partner Member 2019 R2R Secret Santa Build Thread Contributor

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    Thank you for the info as I’ll need a new one soon.
     
  3. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    The dye reagent is usually present in excess, so shouldn't matter too much. :)
     
  4. saltyhog

    saltyhog Valuable Member R2R Supporter Reef Squad Leader R2R Excellence Award Partner Member 2019

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    I dont know why but i always thought the solid reagent was the dye in that test. Thanks for the info, that explains why i didn't notice any difference.
     
  5. madweazl

    madweazl Valuable Member R2R Supporter Build Thread Contributor

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    Did the they change the bottle to make getting evenly sized drops out of it easier? I hate that bottle; I mess up the first drop about 50% of the time and get an extra at the end a lot too. I switched over to the Red Sea Pro which is much easier with my shaky hands.
     
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  6. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    I've not used this kit for more than a decade, so I'm not sure what is in which part, but only the dropwise added titrant is critical in measurement. :)
     
  7. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    Refreshing my memory of it...

    Ca-2 solution is a hydroxide solution to precipitate magnesium hydroxide and prevent it from being detected. The amount of it is not important as long as there is enough to precipitate the magnesium.

    CA-1 is a dye the binds calcium. It is a different color when bound to calcium and when not. The amount is not critical except to provide enough color. It is a weaker binder of calcium than the reagent in CA-3. Less of it may actually give a sharper endpoint, but may be harder to detect visually.

    The titrant (CA-3) is a strong calcium binder (e.g., EDTA, but I'm not certain what exactly they use). As it is added, it binds up calcium. Eventually, the only calcium left that is not already bound to the CA-3 reagent is bound to the dye. At that point more added CA-3 strips away the calcium from the dye, and so the color changes as the dye transitions from calcium bound to free dye.
     
  8. Myka

    Myka Valuable Member

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    So why would they change this? Would it be possible that people with higher Mg, say 1500 or 1600 ppm would not be getting effective Mg precipitation from 8 drops?

    I just did the test both ways (with the new kit that says 10 drops), and I got the exact same answer. Mg is about 1300 ppm.

    Someone I know did the test both ways, one result was 360 ppm and the other was 410 ppm. The Mg is around 1500 ppm. I want to confirm these results - seems odd to me.
     
  9. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    I don't know why they do what they do ( :D ) but that is a possible reason, yes.
     
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