NADPH
Harmless
Posts: 11
Registered: 1-1-2010
Member Is Offline
Mood: No Mood
|
|
Best way to separate NaIO3 from NaI
Hi!
I made NaIO3 by reacting I2 + NaOH => NaIO3 + 5 NaI + 3 H2O
So I tried to separate it from NaI by recrystallization but yield is too low because if I have too saturated solution, NaI also starts to
crystallize.Is there any solvent in which NaI is soluble but NaIO3 completely insoluble? Are there other methods for separating NaIO3 from NaI ?
|
|
|
not_important
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
First, go to http://www.archive.org/search.php?query=subject%3A%22Solubil...
pick a reference, and doiwnload it.
Acetone will work, NaI is quite solubile in it while NaIO3 has rather low solubility.
Another way would to be to add the proper amount of a solubile iodide whose cation's iodate has low solubility. I think SrI2 or BaI2 would work,
getting several references from that search list would allow you to determine for yourself.
|
|
|
NADPH
Harmless
Posts: 11
Registered: 1-1-2010
Member Is Offline
Mood: No Mood
|
|
Thanks! I precipitated NaIO3 with acetone and got ~3x greater yield than by fractional crystallization from water.
When acetone will evaporate I will retrieve elemental iodine from NaI (without risking to make acetone peroxide  ) and try to make also KIO3 (for making KICl4). Can I use K2CO3 instead of KOH for
this?
|
|
|
Jor
National Hazard
Posts: 950
Registered: 21-11-2007
Member Is Offline
Mood: No Mood
|
|
That is a very inefficient way to prepare iodate. You can get iodates in great yield by oxidising iodine with chlorate. You will have to add a few mL
of dilute HNO3, as the reaction proceeds at around pH=2 or lower. Heat until the iodine is completely dissolved. Use a reflux condenser to condense
gaseous iodine (if you don't you will lose some iodine), and push it back in periodically. Next boil away excess chlorine (and some ClO2), and add KOH
until alkali reaction. Crystallise the KIO3 (not sure what to do incase of NaIO3) and recrystallise from water, and dry in an oven at 110C.
You can also electrolyse a solution of sodium iodide in water. I'm not sure about the details, e.g. if potassium dichromate has to be added, what
electrodes have to be used, etc. I know woelen has experience on this.
|
|
|
woelen
Super Administrator
Posts: 8012
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
Iodates can easily be made from potassium iodide. No dichromate needed. You need to electrolyse with a few amperes, using a graphite anode.
Another interesting synth may be this one: http://woelen.homescience.net/science/chem/exps/Na2H3IO6/ind...
From periodates you also can make the tetrachloroiodate(III) compounds.
|
|
|
NADPH
Harmless
Posts: 11
Registered: 1-1-2010
Member Is Offline
Mood: No Mood
|
|
I know it is inefficient way but as I have not fume hood and expensive setup I try to avoid making too much toxic gases.
Maybe I will try to electrolyse some iodide.
|
|
|
NADPH
Harmless
Posts: 11
Registered: 1-1-2010
Member Is Offline
Mood: No Mood
|
|
I hate graphite so I just made some platinum electrodes and test by making KBrO3 from KBr and some ammonium dichromate to improve yield. Works great.
Later I will electrolyse KI.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
