[Verte1]

Hello everybody, this is my first question on the forum but I've been reading it for some weeks already and it's realle interesting. My question is the following:

If I have a solution of 6 L of 96% ethanol and 4% methanol where I introduced 100 ml of H2O2( 35%) and organic matter, how could I mesure the H2O2 that have been destroyed by the reaction with the organic matter? and how do I calculate the amount of NaOH that I have to add to the solution to netralize all the H2O2? Thank you very much for your help.

[Borek]

NaOH doesn't neutralize H₂O₂, so there is something wrong with your question.

Note that while you can determine how much H₂O₂ is left, you won't be able to say how much have been destroyed by reaction with the organic matter, as H₂O₂ decomposes on its own.

[Verte1]

Then, how can I mesure the H2O2 that is left on the solution?, I'm really interested on that. Thanks

[Arkcon]

You can per form a  titration.  You can do a red-ox with permanganate, for a colorimetric endpoint, or do a potentiometric titration.  I quickly Googled these student's methods, but If you have a very serious need, you may want a more rigidly defined method.

[curiouscat]

Adding NaOH to H2O2 might be kind of iffy. I wonder if it will froth and bubble like crazy.

[discodermolide]

If you are careful and add the NaOH drop wise the O₂ release is controllable.
Here is a pic. from one of my experiments. Nachruhrung = Stirring after the addition is complete.
I hope it helps.

[curiouscat]

If you are careful and add the NaOH drop wise the O₂ release is controllable.
Here is a pic. from one of my experiments. Nachruhrung = Stirring after the addition is complete.
I hope it helps.

Interesting! Thanks!

What % was your H2O2? Can you elaborate on why you were mixing them? This sounds very interesting!

[discodermolide]

35% H₂O₂.
We were doing an Evans Aldol, cleavage of the oxazolidinone with LiOOH on a 250kg scale.
We wanted to estimate the amount of oxygen formed so we could guarantee the maintenance of inert conditions (at least below the explosion limit) so therefore we could estimate how much N₂ to pump through the reactor per hour.
On this scale we were abut 20% below the flow capacity of the N₂ system.
The only problem is that when you stop the LiOH addition, oxygen generation continues for a period until the base is consumed. So we had to attach 5 large N₂ cylinders to the reactor in case there was a breakdown of the N2 system and of course stop the LiOH addition.