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How salty is a half salty solution? I mean, only one kind of ion

  1. Dec 8, 2012 #1
    Well....I couldn't fit my question properly in the title. Feel free to propose a way of asking it :biggrin:
    Please note, concentration will be ommited in order to make this topic easier.
    Now, as tongue-d humans we are, we can feel the saltiness of a salt solution. Not a big deal up to here. The salt dissociates into it anion and cation. We have this in the most common salt solution, in water: Na+ and Cl-.
    But, what happens when you have only Na+ without Cl-? Is it salty, half salty or is it somewhere in between? And in a Cl- only solution?
    Isolating ions is supposed to be possible, though I've never seen it.
    You haven't seen PF's server, but keep in mind you rely on it. :tongue2:
     
  2. jcsd
  3. Dec 8, 2012 #2
    you can isolate a SINGLE ion. Or maybe a group of say... 10. That'll require laser cooling and extremely precise measurements.

    But in a solution there's something like 10^20-10^23. Even the most dilute solutions measurable have concentrations of 10^10 ions per liter. You simply can't do it.
     
  4. Dec 8, 2012 #3
    The reason I said that was sort-of-using what a teacher said when explaining low-solubility salts. It was something like "If you mix two solutions, one with sulfide ions and other with Fe+3, they become one in the salt and precipitate quickly". So I thought it was possible.
    Or...was it a way of explaining how those salts work, without considering actual experimental difficulties?? :confused:
     
  5. Dec 8, 2012 #4

    jim mcnamara

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    NaOH dissociates into Na and OH ions and is a strong base. HCl dissociates into H and Cl ions and is a strong acid. Either of these in moderate concentration may severely damage your mouth, tongue, esophagus when consumed.

    NaCl dissociates into Na and Cl ions. So it is neither a strong acid nor a strong base.
    Salt in moderate contration is a food stuff - pickle juice. Not that I am pushing pickle juice as a food, but it used to make, well, pickles, and when you consume pickles you get some dissolved NaCl. In a moderate concentration.

    Reiswitter - does that show you why the way you asked your question does not make sense to us? I don't get what you want to know.
     
  6. Dec 8, 2012 #5
    No problem up to here. I'm assuming that a human-noticeable quantity of Na+ can be isolated, because, I heard it happening with sulfide. With those ions a solution could be made, and it could or not feel salty, because it lacks the Cl- ions in a normal salt solution.

    My username wreacks havoc again :rofl::rofl::rofl::rofl:
    Rephrased, my question becomes: "Would a Na+ ONLY water solution FEEL as salty as a NaCl one?"
     
    Last edited: Dec 8, 2012
  7. Dec 8, 2012 #6
    I would call it a very high voltage solution!
    Maybe even an electroheavy solution!

    Sodium ions are positive. If you add sodium ions without negative ions to water, then the
    solution will have a very large positive charge.

    The large positive charge will produce a high positive voltage relative to the voltage at infinite distance. The precise value would depend on the capacitance of the solution, which may depend on the geometry. I leave it as an exercise in electromagnetic theory as to what the capacitance of this solution would be.

    Also note that like charges repel. So the sodium ions will repel each other. You may have sodium ions jumping out of the water, accelerating outward.

    The positive charge could be passed to water molecules, so you may have protons and hydroxyl ions jumping out of the water.

    On the other hand, unlike charges attract. So you would have electrons accelerating toward the solution. Electrons would accelerate and hit the surface of the solution at high speed.


    There was a song a few decades back called "White Lightning". I think it would taste like that!
     
  8. Dec 8, 2012 #7

    Ygggdrasil

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    The taste of NaCl is primarily due to taste cells that sense the presence of sodium ions through their sodium channels. Therefore, salts containing chloride but lacking sodium, such as RbCl or CsCl will not taste salty. Conversely, salts containing sodium but lacking chloride, such as NaNO2 or Na2SO4 will taste salty.

    https://en.wikipedia.org/wiki/Taste#Saltiness
     
  9. Dec 9, 2012 #8

    SteamKing

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    How does something 'feel' salty?
     
  10. Dec 9, 2012 #9

    Integral

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    Guess you have never swam in the ocean.

    Na when introduced to water reacts violently. During a boot camp demonstration a instructor dropped a fist sized chuck of Na into a 55gal drum of water. It immediately launched straight up about 50'.
     
  11. Dec 9, 2012 #10

    Borek

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    Where does it say "separation of ions"?
     
  12. Dec 9, 2012 #11

    DrDu

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    I once tasted both RbCl and CsCl and they both taste kind of salty although not exactly like rocksalt. You can buy salt substitute which contains KCl. So situation is not that easy.
     
  13. Dec 9, 2012 #12
    Weissritter, your proposal for a solution containing only a single species of ion fails at the first hurdle since there must also be solvent ions present in an ionic solution, even if it were possible to support a single species in such a solution.

    Isolating ions is possible, but surely, by the definition of isolation they are not in solution?

    Ions exist in plasmas, and can be separated by electric and or magnetic fields, but these are not in solution and most definitely not for tasting.

    If you are interested in an introductory treatment of the chemistry of taste look in the book

    Molecules by Atkins

    https://www.amazon.com/Atkins-Molecules-Peter/dp/0521535360
     
    Last edited by a moderator: May 6, 2017
  14. Dec 9, 2012 #13
    This was the answer I was looking for. In my defense, I can say my native-language wiki doesn't cover which salts are the 'salty' feeling ones. I'll add it soon.
    Sounds like the tongue detects them as if they were sodium, as they react the same way, but their way bigger atomic radius prevents many atoms to be detected at the same time, maybe?



    I didn't ask for this but neither saw it coming. You remembered me the obvious I forgot to see, and you deserve a thank you. Seriously. You could feel your tongue electrons being pulled towards the solution :surprised

    Taste salty, I mean taste salty.
    I was a child once, I was weak to bigger-than-me waves once, I don't remember how, but I ended up doing a somersault by the effects of the wave force in me and swallowing a lot of water. It was horrible. But you'll find something else than Na and K in water, I guess, like Li or d-group metals, right?
    By adding metallic sodium to water you get NaOH, and a lot of energy. So the way here would start with a common salt with non-explosive sodium.

    It doesn't say, I only thought it could be done since I deducted it from that statement. A while ago I thought it was possible.
    Anyway, Ygggdrasil's answer fills the doubt.


    Yeah...I didn't explain properly. I meant to take all the chloride (well, not all, but the most) in a NaCl solution, ending up in "only Na+ solution", which could or not feel salty, but Ygggdrasil ended up explaining.
     
    Last edited by a moderator: May 6, 2017
  15. Dec 9, 2012 #14
    Several have told you that you cannot have a solution containing only one type of ion.
    Yet you still persist in posting as though this is possible.

    This is very confusing.

    As an addition to the information supplied by Ygggdrasil you might like to note that pure sodium chloride tastes less 'salty' than impure.

    This is one reason why some prefer to buy 'iodised salt' or sea salt for cooking. Potassium iodate offers neither chloride nor sodium ions.
     
  16. Dec 9, 2012 #15

    Ygggdrasil

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    Yes, as the wikipedia article says, the sodium channels can detect other similar cations, just less efficiently. For example, it states that KCl tastes about half as salty as NaCl. So I agree with DrDu that, as with most things in biology, things are not so simple. But the point remains that salty taste is due to the sodium part of NaCl and not the chloride part.

    I think the main reason why people buy iodized salt is not for the taste, but because iodine is an essential nutrient and iodized salt can help prevent iodine deficiency.


    With regard to taste vs feel, these two senses are not so different in some cases. Foods that taste spicy often contain the molecule capsaicin. Capsaicin activates a channel called TRPV1, which is normally activated by hot temperatures. Similarly, mint flavor contain molecules that activate cold-sensing channels like TRPM8. Other spicy foods (such as Sichuan peppers) can contain molecules that activate other pain receptors as well.
     
  17. Dec 9, 2012 #16
    The song was actually on a related topic. It described the behavioral and physiological effects of a dilute solution of water in ethanol, nicknamed "White Lightning". "White Lightning" is also called "Hill Billy Heroin" and "Clear-All".

    The picturesque effects presented in the song almost as interesting as my conjecture of what an aqueous Na+ solution would be like. The difference is that "White Lightening" is a REAL drink.
     
  18. Dec 9, 2012 #17
    I'll ask my teacher directly as soon as I see him again. Thanks for siding with truth.

    You've unraveled a mystery I had for some years. Thanks!

    :surprised :surprised
     
  19. Dec 9, 2012 #18

    Sodium ions are much smaller than chloride ions so
    I could imagine a container, separated into two by a semi permeable membrane, such that only the sodium ions (edit and possibly solvent ions) could pass through.

    Put pure water into one half and salt solution into the other.
    The chloride ions would remain in one half of the container, but the pure water half would soon contain some sodium ions that had passed through so you would have some solution containing only one species of solute ion.

    However as I already noted in post#12 there would also be other ions in the pure water half, due to some ionic dissociation of the solvent water.

    Can you guess what else would happen to maintain electrical neutrality?
     
    Last edited: Dec 9, 2012
  20. Dec 9, 2012 #19
    As said before, electrons would be attracted, and that's how much I can guess. Electron jumping from s sublevel to higher ones sounds too much to be possible, so the best I can guess is the electron-leeching effect.
     
  21. Dec 10, 2012 #20

    Borek

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    Electrons would stick to their ions, so they would not change the charge distribution.

    If anything I would expect to see changes in the concentrations of other ions in the solution.

    Please remember that moving ions through the membrane as Studiot suggested means creating charge separation. Charge separation means potential difference - and any measurable change in concentrations would require pretty high voltages.
     
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