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Thread: Why can't I use tap water?

  1. #17
    jeff 2's Avatar
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    it is possible to use top water , but attention to the chlore .

    for the drosophyllum see here their condition 'in situ'
    Pnguicula & Cie

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    mobile's Avatar
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    Without running thorough test for what is dissolved in your tap water, everytime you want to use it, the only way of telling if your plants are OK with it is to risk it and give it a try. If you can't take the risk then stick to RO water. pH and TDS vary from area to area and even season to season, so you can't really get a conclusive answer. One persons experience can be different from anothers due to locale. Personally, I think that there are a lot of myths with regards to how intolerant CPs are, many of them based on how they grow in their natural environment. For instance, it is often assumed that because they naturally grow in a typically nutrient poor environment then any soil nutrients will kill them but this is not necessarily true. However, enevitably there will be a limit to their tolerance, as with all plants.

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    Quote Originally Posted by Not a Number View Post
    It would depend on the nature of the buffer, the beginning and target pH and the nature and extent of the acid/base reactions in question.
    Can you give an example? Let us say we start off with tap water made alkaline by dissolved calcium carbonate and we want to decrease the pH to 7 and get rid of the mineral ions.

  4. #20
    CPlantaholic's Avatar
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    I'll try to give a general (hopefully correct) explanation...

    Basic buffers, like calcium carbonate work by keeping hydronium ions (H+ or H3O+) "occupied," which would normally contribute to lowering the pH of the solution.

    For example, normally, if you added hydrochloric acid (HCl) to a glass of water, this reaction would occur:
    HCl+H20--->Cl- (aqueous) + H30+

    Notice that since the H30+ is "free" on the right side of the equation, it contributes to lowering the pH (a measure of the concentration of hydronium ions in solution).

    First, adding calcium carbonate (CaCO3) to water, it will lower the pH slightly, but it won't contribute OH- ions, so its effects won't be as dramatic on raising the pH compared to if you poured the same mass of of sodium hydroxide into solution (see the paragraph below this for an example).
    So if you add HCl to CaCO3, the main reaction would be the following (ignoring other side-reactions that would take place in solution, for simplicity):
    2HCl+ CaCO3(s)---> CaCl2(aqueous) + H20 +C02
    HCO3- and H2CO3 could also be formed in solution, but in all of these cases, the hydronium ions would be kept "occupied" more often and would not contribute to raising the pH as much.

    Just to give another perspective- modifying an idea from wikipedia:
    Water can dissolve up to 15.9 grams/Liter of CaCO3 and still maintain a pH of 7. Converting this to molarity, gets you a 0.16 mole/L solution of CaCO3 that will still have a pH of 7.
    Compare that to sodium hydroxide, which with the same molarity of 0.16 mole/L (6.4 grams/L) would equate to a pH of 13.2. So calcium carbonate is able to counteract the addition of acids to solution without significantly raising the pH, themselves.

    Please, NaN, or anyone- correct me if I'm wrong on anything!!!! I took chemistry 2 and a half years ago, so it's quite a bit fuzzier than it used to be.
    And here's a helpful resource I used back in the day to try and understand buffers: http://www.chemguide.co.uk/physical/...a/buffers.html
    Visit The Sundew Grow Guides: http://www.growsundews.com
    New- Drosera video tours & other sundew info, now on YouTube!

    Happy Growing!

  5. #21
    Hello, I must be going... Not a Number's Avatar
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    No use asking me, freshman and high school chemistry was nearly 40 years or so ago. Use it or lose it.
    Grand Hotel... always the same. People come, people go. Nothing ever happens.

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    jurow, good reply! This has been good info, and do not take lightly for we all care far too much about the health of our CPs! Thanks

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