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Isolating NaNO3 from NaCH3COO

  1. Aug 8, 2010 #1
    How would it be done? Would fractional crystallization work?
     
  2. jcsd
  3. Aug 8, 2010 #2
    Are you sure you haven't committed any spelling mistakes?

    NaNO3 (silver nitrate) contains nitrogen atoms, so it can't be isolated from NaCH3COO, since the latter doesn't contain it.
     
  4. Aug 9, 2010 #3

    Borek

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    Staff: Mentor

    Most likely cnidocyte has a mixture of both salts and wants to separate them. But you are probably right that the wording is not the best.
     
    Last edited by a moderator: Aug 13, 2013
  5. Aug 9, 2010 #4
    Yeah thats what I meant, I have a mixture of composed of solid sodium nitrate and solid sodium acetate and I want to separate the 2.
     
  6. Aug 9, 2010 #5
    Well, both salts are quite soluble in water, so cristallization, although possible, will take a long time to effectively separate them.
     
  7. Aug 9, 2010 #6
    just some suggestions:

    you can possibly heat up the mixture with concentrated sulphuric acid. the ethanoate will presumably esterify with another alcohol that you are using and give you a nice ester layer floating on the top. after that hydrolyze the ester back into the ethanoic acid and then heat it up a bit to evaporate the alcohol. add some NaOH and you get back sodium ethanoate.

    you'll have a bit of problem getting the sodium nitrate out of the sulphuric acid though :tongue:

    maybe you can also try electrolysing the mixture and try to reduce the nitrate ion into nitrogen dioxide and water. i'm not really sure if that'd work though.
     
    Last edited: Aug 9, 2010
  8. Aug 10, 2010 #7
    Didn't realize it was this difficult to separate these 2 salts. I learn all these chemistry skills I learned in the lab at my college but when it comes to actually separating 2 salts in a real life situation I'm powerless lol.

    I wondered what would happen if I ran current through the solution. I'm guessing the Na+ ions would be reduced and end up forming NaOH but I've no idea what would happen to the nitrate and acetate ions. I'm a beginner so NO2 scares the crap out of me I'd rather not have to deal with that just yet.
     
    Last edited: Aug 10, 2010
  9. Aug 10, 2010 #8
    If you only wanted the silver nitrate, you could precipitate Ag in the form of AgCl (using sodium chloride), and, from the precipitate, reduce AgCl to Ag. After, you'd let the Ag to react with some nitric acid, getting the nitrate back.

    I don't know how to reduce AgCl to Ag in a safe way, however. You could melt AgCl (BP = 457) and perform an electrolysis.

    And remember of always doing potentially harmful experiments in a fume hood.
     
  10. Aug 10, 2010 #9
    Lol where are you getting silver from? This threads about sodium nitrate and sodium acetate.
     
  11. Aug 10, 2010 #10
    Na+ is extremely hard to be reduced because it has a very negative redox potential so i wouldn't worry about that. but unless you control the voltage really really well you will end up reducing nitrate into all kinds of compounds like nitric acid, ammonium and NO2 which will make matter worse.

    i think esterification is a more promising way to separate out the acetate. you just need to find a solid catalyst (some transition metal maybe) that doesn't go into the solution and can be easily filtrated out afterwards. what's left should be pure nitrate, and you can easily hydrolyze the ester back into alcohol and acetic acid with just dilute NaOH and a little heat, evaporate the alcohol and end up with sodium acetate again.
     
  12. Aug 10, 2010 #11
    @cnidocyte: OH BOY!
    I think I was sleepy when writing that post!

    Please ignore it.
     
  13. Aug 10, 2010 #12

    Borek

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    Apart from the well established fact that this thread is not about Ag :wink:, reduction shouldn't be that hard - plenty of known methods. Just adding some ammonia solution and doing electrolysis should be sufficient.
     
  14. Aug 10, 2010 #13
    @Borek

    Could you send me a PM about those methods of reducing Ag+ to Ag?
     
  15. Aug 10, 2010 #14
    @Borek

    You can just displace the Ag+ out of the solution by throwing any metal above Ag in the reactivity series. You don't even need to go into electrolysis. Silver is one of the least reactive metals, beaten only by a handful like mercury, gold and platinum. (You do need to get AgCl to dissolve anyway, by adding ammonia as you said.)
     
    Last edited: Aug 10, 2010
  16. Aug 10, 2010 #15
    @Borek, arkofnoah and myself:

    This silver reduction is disturbing the discussion... And it is my fault!

    Let's come back to the OP's problem. How can one separate a sodium acetate and sodium nitrate mixture?
     
    Last edited: Aug 10, 2010
  17. Aug 10, 2010 #16

    Borek

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    Google for recovery of silver from photographic solutions.

    Yes - silver can be easily displaced. However, saturated solution of AgCl has very low concentration of Ag+, around 10-5M, that lowers formal reduction potential by about 300 mV. It is still not very difficult to reduce Ag+, but not as easy as it may seem at first sight.

    Then there is a problem with reaction speed. If you just put piece of copper into saturated AgCl solution, you will need a lot of time for a substantial amount of Ag to get reduced, as speed of the reaction is limited by maximum possible concentration of Ag+. Note that after reduction concentration of chlorides goes up, which further lowers Ag+ concentration and reaction speed. Hence addition of some complexing agent speeds up the process substantially.
     
    Last edited by a moderator: Aug 13, 2013
  18. Aug 10, 2010 #17
    @borek: well we can always heat up the AgCl solution to increase solubility and add more reactive metals like zinc or magnesium powder (lol why copper of all metals?). but i agree that it's still not so feasible for AgCl because of the solubility constraints. but nevermind, this is off-topic :smile:
     
    Last edited: Aug 10, 2010
  19. Aug 10, 2010 #18
    You mix AgCl to a much more amount of Na2CO3 and then you heat at several hundreds of °C in a crucible:

    2AgCl + Na2CO3 --> heat --> 2Ag + 2NaCl + CO2 + (1/2)O2
     
  20. Aug 10, 2010 #19
    And approximately which are the relative amounts? If the nitrate were less than the acetate, I think fractional crystallization could work since at 0°C for ex. the nitrate is doubly soluble than the acetate.
     
  21. Aug 11, 2010 #20
    Around 60% sodium nitrate.
     
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