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actionclaw

Will calcium carbonate neutralize acetic acid?

Though it certainly could have hydroponic applications, this is not strictly a hydroponics related question. My thinking was that there may be more high-tech, scientific types hanging out in this area that might be better suited to answer this question.

For the last few years l've been saving all our egg shells, drying them in the oven by pilot light, using a coffee grinder to grind them into powder and then adding them to the tomato plants' soil. I realize others dispute this but my own informal testing and anecdotal experience has demonstrated to me that it does make a difference.. a considerable one at that.

Recently, I've been considering possible methods to, either, extract more of the calcium carbonate or break it down to make it accessible sooner. I know that vinegar can dissolve the shells to release the calcium carbonate but I also know that vinegar can act as an herbicide.

  • Is it the acetic acid or something else in vinegar that makes it harmful to plants?

  • Does the interaction with the calcium carbonate neutralize vinegar's deleterious effect?

  • If not, is there another element that could be introduced that would neutralize vinegar's herbicidal properties while retaining (or possibly even adding to) any beneficial elements?

    (just enough baking soda to balance the ph, for example?)

Thanks for any input

Comments (7)

  • freemangreens
    14 years ago

    It's been about 40 years since college chemestry, so let me just tell you this: I'm a plumbing contractor and for people who pee in their toilets and don't flush right away ("If it's yellow, let it mellow" mentality), the chlorine in the water reacts with the soluble carbonates in urine and they precipitate out (form solids inside the toilet). This eventually causes the toilet to flush incorrectly.

    I said all that to say this: Adding vinegar (acetic acid) will soften the concretions over time. So, to answer your question, if asked in reverse: Yes!

    Adding any kind or any amount of acid to your hydroponic set-up will drastically affect the pH!

    Hope that helps some.

  • bilberrybrian
    14 years ago

    Some commercial growers will use nitric acid to neutralize calcium carbonate and magnesium carbonate in their water. I believe the products from the reactions are magnesium nitrate, calcium nitrate and carbon dioxide. Concentrated nitric acid is too dangerous for a person to keep around their house or garage though.

    Vinegar is a dilute acetic acid. Acetic acid is what hurts the plants. Concentrated forms of it are sold as more environmentally friendly contact herbicide which you can read about here:

    http://www.pesticide.org/pubs/alts/weeds/vinegarinherbicides.html

    This source says the acidic qualities destroy the cell walls if the acetic acid is sufficiently concentrated. Spraying the vinegar we keep in our kitchens may not do the job for much more than small juvenile weeds.

    If this were indeed true then calcium carbonate should diminish the effect. The acetic acid would form partially into calcium acetate and neutralize it's acetic pH. Calcium acetate's pH is about 7.5, according to this MSDS.

    http://www.jtbaker.com/msds/englishhtml/c0266.htm

    According to wikipedia calcium acetate is used as an additive in candy. Who knew? You could try mixing acetic acid with classroom chalk or tums, then applying it to a plant and/or soil and see what happens. If you use baking soda you will be introducing some sodium which isn't going to be desirable.

  • ActionClaw (Northern Ohio zone:5a/5b)
    Original Author
    14 years ago

    With a bit more searching I found this subject has already been discussed .. and right here on this very forum! Starting with third post.
    "I get soluble calcium by dissolving sea shells in vinegar. Let ±50g of shells soak in 1 liter of white vinegar. After about 24 hours you can boil the lot in a stainless steel pot for about an hour. Then filter the liquid (I use a coffee filter [LOL]) to remove the excess of shells and make-up the volume to 1 litre.
    This way you obtain a calcium acetate solution that contains 15 grams of calcium per litre."

    "? Are you able to estimate the grams of Ca that egg shells, substituted for sea shells, would yield in your formulation ?
    (The egg shell in vinegar extract, for soluble calcium, was told me by an old country doctor over a quarter of a century ago for use as a human nutritional supplement of calcium.)"

    "It would be the same.
    The amount of calcium(Ca) that will dissolve as acetate in 1L of white vinegar (5%) - irrespective of its source - is ±15g (in theory: 16.7g).
    Just dissolve egg shells untill they no longer dissolve."

    "when making the calcium acetate, is boiling required? and what does that part do? I was thinking of just dumping egg shells and vinegar into a glass bottle then skimming liquid off the top as needed as a calcium supplement. since the concentraition will always be 15ppm, the idea is just get as much as required for the concentration I want to make up."

    "I suppose that could work. The boiling is intended to remove any residual acid. Maybe you should test the pH to make sure(?)"

  • freemangreens
    14 years ago

    I knew this looked familiar. Ask Greystoke about this. He's the Garden Web chemistry guru in my opinion.

  • ActionClaw (Northern Ohio zone:5a/5b)
    Original Author
    14 years ago

    Good call. He's exactly who started the above!

    Here is a link that might be useful: Cited Post

  • greystoke
    14 years ago

    What is there to say? Most has been said, except . . . I do not believe that vinegar itself (as opposed to other mild acids, such as citric acid) is a herbicide. I think its just the acidity that does the trick (in my opinion). So . . if you neutralize it with calcium, the effect should be gone.
    Besides . . . I've used this for years without any bad results. It's handy to have around when you need to add calcium.

  • jamesvlad
    13 years ago

    Hello there! I hope I´m not too late.
    Plants can only absorb soluble calcium, and the eggshells are Calcium Carbonate that is very insoluble. So it´s better to buy some cheap Calcium Carbonate than using eggshells. But you have to disolve Calcium Carbonate. Wait!! there´s a little secret.
    Easy! Just add to Calcium Carbonate some water and Citric Acid. Citric Acid complex calcium and eliminates carbonate (CO2), and it´s a very acid with buffer capacity. ;-)
    How much you may ask? That´s your work!

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