LuckyWinner
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Sodium Iodide does Not Dissolve in Acetone? Why?
Made NaI by
(6)NaOH + (3)I2 --> NaIO3 + (5)NaI + (3)H2O
used exact stoichemsitry amounts.
added iodine to hot NaOh+ distilled water solution with mag stirring at 150C.
dried in oven at 150C to dryness.
scraped up pure white crystals from glass pyrex dish.
TRIED TO dissolve the NaI in acetone and only a small fraction
was absorbed.
acetone was heated to 45C with heavy mag stirring!
this was done cause NaIO3 is insoluble in acetone!
to separate these 2 compounds!
acetone was dried over calcium sulfate for several days!
Crystals were grinded into powder!!!
the fraction that was absorbed by the acetone
was slightly orange... this is caused by acetone self aldol condnesating
by excess NaOh present???
was slightly orange tinted with a 'funky' smell!
could it be that some adjustment in this reaction causes a MAJORITY
of NaIO3 being produced INSTEAD OF NaI !!
Too much OXIDIZER left in the IODINE?
WHats going on?
[Edited on 23-11-2020 by LuckyWinner]
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CharlieA
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In general, ionic compounds (like NaI and NaIO3) are soluble in polar solvents. Acetone is only very slightly polar and would not be
expected to dissolve large amounts of ionic compounds in relatively small amounts of acetone.
Evaporating your reaction mixture to driness just produced a mixture of the iodide and the iodate, both of which are white crystals and both soluble
in water (a very polar solvent).
For a general solubility rule, I always remember: avi cum avibus, simili congregantur.
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DraconicAcid
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Quote: Originally posted by CharlieA  | | In general, ionic compounds (like NaI and NaIO3) are soluble in polar solvents. Acetone is only very slightly polar and would not be
expected to dissolve large amounts of ionic compounds in relatively small amounts of acetone. |
Actually sodium iodide is quite soluble in acetone (something like 15% by weight, IIRC). It's very useful for metathesis reactions with other
halides, because sodium chloride and bromide are far less soluble, and precipitate nicely from dry acetone.
http://chemister.ru/Database/properties-en.php?id=760 gives 30 g NaI per 100 g acetone at 20 oC.
[Edited on 23-11-2020 by DraconicAcid]
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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LuckyWinner
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Solubility of NaI in acetone is found to be 29.2% by weight at 25 ∘C
For example, the solubility of NaI in acetone is found to be 29.2% by weight at 25 ∘C but it is increased to 40.5% when 6.1% (by weight) of water
added to the solution
https://chemistry.stackexchange.com/questions/116396/why-doe...
acetone
0.784g/cm3
100ml = 78.4g ,
29.2% of that is 22.89g of NaI can be absorbed by 100ml of acetone.
-----------------------------------------------------------------------
https://pubchem.ncbi.nlm.nih.gov/compound/Sodium-iodide
39.9 G IN ACETONE @ 25 °C at 100ml
strange that both sources give 2x different solubility .... maybe pubchem is talking about
non anhydrous acetone?
anyhow anyone got an answer to my question?
I forgot to add that I want to separate the NaI from the sodium iodate.
[Edited on 23-11-2020 by LuckyWinner]
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Boffis
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@ Luckywinner, If you are trying to separation the mixture of sodium iodate and sodium iodide produced by this reaction it is easily done. Simply
leave the dried powder in a glass bowl exposed to the air. After a few days the the NaI will have deliquesced to a liquid and the NaIO3 will be left
behind as a white powder. I you now cover it and leave if for a month the iodate will slowly turn into beautiful crystals. Iodate its practically
insoluble in saturated NaI so the amount of iodate in the filtrate will be very small. If you want your NaI analytically pure add a couple of drops of
dilute HI solution and then pass H2S into it until the solution is white and then boil to coagulate the sulphur, cool, neutralise carefully with NaOH
and filter. The resulting solution can then be evaporated to dryness as before and is now very pure NaI. Remember it absorbs water from the air
rapidly. The NaIO3 is also very pure and just needs washing with a little cold water.
If you are going to use acetone to recover the iodide how about using a soxhlet extractor?
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LuckyWinner
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| Quote: Originally posted by Boffis | @ Luckywinner, If you are trying to separation the mixture of sodium iodate and sodium iodide produced by this reaction it is easily done. Simply
leave the dried powder in a glass bowl exposed to the air. After a few days the the NaI will have deliquesced to a liquid and the NaIO3 will be left
behind as a white powder. I you now cover it and leave if for a month the iodate will slowly turn into beautiful crystals. Iodate its practically
insoluble in saturated NaI so the amount of iodate in the filtrate will be very small. If you want your NaI analytically pure add a couple of drops of
dilute HI solution and then pass H2S into it until the solution is white and then boil to coagulate the sulphur, cool, neutralise carefully with NaOH
and filter. The resulting solution can then be evaporated to dryness as before and is now very pure NaI. Remember it absorbs water from the air
rapidly. The NaIO3 is also very pure and just needs washing with a little cold water.
If you are going to use acetone to recover the iodide how about using a soxhlet extractor? |
thanks, thats good data.
I observed the NaI that was extracted with acetone forming a puddle upon exposure to air. your method seems good but takes quite some time.
what about putting NaI and NaIO3 into a furnace at 450C
, this should remove the oxygens from the NaIO3 and leave only NaI.
how long does this process take in the furnace,
1 hour at 450C should be enough?
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