Sodium Iodide

[johnd]

We are trying to make Sodium Iodide 57% solution using NaOH 50% and crude Iodine. We finish with a pH of the solution of approx 12, when we try to drop the pH to approx 8.5-9, the solution becomes deeply colored. Can someone help with what we are doing wrong??

 

 

Thank

 

Johnd

[John Cuthber]

You have forgotten to add a reducing agent.

[johnd]

Thanks for the reply, maybe we aren't using the sequence. We are using formic acid as the reducing agent, putting the formic in after the reaction, however when it drops the pH, we get the iodine color in the solution. Can you recommend a procedure??

 

Thanks,

 

Johnd

 

You have forgotten to add a reducing agent.

[John Cuthber]

At best, the reaction of iodine with formic acid is rather slow.

 

IIRC the industrial process uses iron filings to convert iodine to ferrous iodide then the solution is treated with NaOH to ppt Fe(OH)2 and leave NaI in solution.

 

 

Why are you trying to do this?

[johnd]

We manufacture Iodophors and currently purchase Hydriodic Acid and cude iodine in the process. We're looking to produce Sodium Iodide to replace the use and expense of Hydriodic Acid. Would you be interested in acting as a consultant in this project?

 

At best, the reaction of iodine with formic acid is rather slow.

 

IIRC the industrial process uses iron filings to convert iodine to ferrous iodide then the solution is treated with NaOH to ppt Fe(OH)2 and leave NaI in solution.

 

 

Why are you trying to do this?

[John Cuthber]

I'm not interested in consultancy work ( though it's flattering to be asked).

However I would look at using formalin as a reducing agent.

Things like this

http://books.google.co.uk/books?id=aUW98Hhv9GoC&pg=PA233&lpg=PA233&dq=romijn's+method+formaldehyde&source=bl&ots=0jYx6QZ1R6&sig=QbU8FBU560wZvlbFDDkrU8PaDjM&sa=X&ei=_tYzUKLpOauZ0QW5t4HQBw&sqi=2&ved=0CBcQ6AEwAQ#v=onepage&q=romijn's%20method%20formaldehyde&f=false

suggest the reaction is reasonably fast and goes to completion.

I don't know how the economics of it work.