Alternatives for Sodium Bisulfite

[Vaaguh]

During a post cleanup after the reduction of (Pseudo)Ephedrine with RP/I there is used Sodium Bisulfite, are there any alternatives that could be used perhaps Sodium Bicarbonate?

[Vitus_Verdegast]

Isn't that for working up the excess iodine, as it reduces I₂ ^__> 2I^-

I guess Na thiosulfate could be used too, but bicarbonate will not work for this purpose.

You can use the Na metabisulfite you find at a brewer's store, when water is added to this, it makes an aqueous solution of NaHSO₃.

[Vaaguh]

thanks for the information,

Yes it is indeed for removing the excess of iodine.

Metabisulfite it is then  

[Osmium]

This step can be omitted, it's absolutely not necessary.
It might fuck with your iodine recovery attemps, so keep those sulfur compounds out of the reaction.

[mr_pyrex]

What ^ he said plus...all you need to do if you think you have left over I in your finished rxn solution is to uncap your reaction vessel from your push/pull setup and add say an equal volume of Dh20 as you have in your reaction vessel and then heat it up around 90-95'C for 10-15 minutes, this should drive off any residual Iodine or at least as much as you need to be concerned with.   Pyrex out of advise

[amalgum]

SWIM always uses sodium sulfite.

[halfkast]

amalgum what industry is sodium sulfite used in bee? swihk has looked for it briefly before.

I have searched the fs kinda, but not hard enough obviously because i doubt its that hard to find.

[stereoIsomer]

The main concern is removing excess I2 which is unpleasant to have in the final product, right ? If so, simply heating the post-rxn results to a low boil for 5-10 mins will result in excess I2 to evaporate, leaving you with clean product. Is your goal to recapture excess I2 for later re-use in future reactions ? (swim does not advice about this, sorry... but perhaps someone else does)

[amalgum]

halfkast-
Photography.  Beleive people when they say for chemists like us should take it up as a hobby, cause you would be surprised to see the myriad of shit SWIM has just for photogrophy (and they all have legit use).  From phenols to quinones, and salts ga-fucking-lore, from pure KI to HgNO3.  Palladium salts to.  As long as you walk in to a photography shop and say "Give me two pounds of so and so for a certain toner mix I want to try, and a couple pounds of this for this developer I'm working on" and nobody gives a damn.  Basically I'm saying somethings you get from a photography store, it would help to know the background for it's legit uses.   Something like sodium sulfite isn't suspicious at all.  I mean they'll laugh if you try to buy anything less than a pound jar you know what I'm saying.

[Osmium]

Listen up class!
Once your reaction is done there won't be much I2 left, if at all. Can anyone explain to me how I2 is supposed to show up in the end product, when you
1. wash the still acidic, diluted reaction mixture with a NP,
and then
2. basify the shit out of the reaction mixture with NaOH?
How can I2 survive strong basic pH???

There is no reason to try to remove I2 with sulfite or thiosulfate, this will only complicate further workup.

Anyone ever seen what happens when a solution of thiosulfate is acidified?

[halfkast]

amalgum yes you were very clear man, I know what you is sayin'.  

Os I heard ya the first time.

[abolt]

Anyone ever seen what happens when a solution of thiosulfate is acidified?

No.............and?

[Vitus_Verdegast]

Na₂S₂O₃ + 2H^{+ __}> SO₂ + S + H₂O + 2Na⁺

Sulfur dioxide is a colorless, poisonous, very sharp smelling and irritating gas.

[halfkast]

Upon YOUR suggestion that has been up for about 4 days in the stimulants forum.

I guess Na thiosulfate could be used too, but bicarbonate will not work for this purpose.

[Osmium]

> SO2 my friend...

It's not the SO2 that is the problem, it is the very fine sulfur that precipitates that will cause you problems.

[Vitus_Verdegast]

Get off my back will you?
And open a fucking book sometimes, before you start to whine.

No matter if it is an aqueous solution of thiosulfate, sulfite or bisulfite, acidifying will always cause SO₂ to evolve. Capiche?

[Osmium]

> Get off my back will you?

Huh?

> And open a fucking book sometimes, before you start to whine.

Did I whine???
Is it full moon or why are you so sensitive?

[hypo]

Halfbrain should probably mean halfkast  

(who's sensitive?   )

[amalgum]

Yeah that is true, as long as the reaction is completely done, there shouldn't be any I2 left.  SWIM always used just a little bit as a precaution.  Plus sometimes if the rp isn't to clean and after it tends to clump, Na2SO2 seems to loosen it pretty nicely sometimes.

[WizardX]

Starch is used in analytical chemistry as an endpoint indicator (dark blue colour) for I2. After your HI/RP reduction and work-up/purification to the meth freebase; by adding one drop to a starch solution and a resulting dark blue colour is observed, then I2 is present.