[Yoritomo]

Hello,

     I'm using Orthophosphoric Acid for mineral specimen retouching and I face difficulties on neutralizing the acid.I use Sodium Bicarbonate for neutralization and I need 1 kilo to neutralize 500 ml 30% of the acid. Plus, the process is very slow and I have to add small amounts of S.Bicarbonate at a time so that the foam produced remains inside the container.

     Is there any other compound that could be used so that the neutralization gets easier?


     Thaks a lot in advance!

         _Kostas.

[Borek]

You can try sodium hydroxide - there will be no gas evolving and mass needed will be around half that of bicarbonate.

However, bicarbonate leaves almost neutral residue, while NaOH is highly caustic. So while neutralization will be faster, you may damage your specimens.

[Yoritomo]

Hello!

        Thank you for your answer! The Sodium Hydroxide is still an option, since I can remove the specimen before I neutralize the solution. However,if the solution turns highly basic, the new question is how do I turn it neutral so that I can discard it safely.

         Also, is the application of NaOH safe, or an explosion will result?


  Thx a lot!
   
       -Kostas.

[Borek]

No explosion risks. The only problem is that it is caustic, but as far as I remember it is less dangerous than the phosphoric acid you are already using. According to my memory phosphoric acid burns heal worse than sodium hydroxide burns (but it wasn't me who got burnt, so I can be wrong).

And after neutralization you may use the same bicarbonate to neutralize excess hydroxide. No gas evolving this time.

[macman104]

I used 50% NaOH to neutralize strong acids in the organic lab very frequently.

Also, if you try this, and the reaction seems too violent and splashes, you can dilute the acid into more water.

[Yoritomo]

Thank you all very much for your answers!

         At the percent I use it, the Phosphoric has to be less corrosive for the tissues than the NaOH. Cola also contains the acid. I will make an experiment and let you know the result!



     Thanks!
      -K.