disposal of oxalic acid

[kmd]

Hi everyone,
I have made saturated oxalic acid (about 100mL )for a yr 11 experiment. The CSIS appendix D says it's ok to put it down the sink after making it pH: 8-10.
Could anyone please tell me which chemical I add, and how much?
Thanks heaps.
Kirin

[sunray18]

I would try putting a small amount in a beaker and adding sodium bicarb to it and see what happens.. universal indicator should show when ph is neutral.. then if this works and is not too exothermic, apply similar technique to the rest of the solution..
I hear it is a great wash for driveways and paths.. so maybe the groundsman could use it!

[kmd]

thanks for that. I'll give it a try.

[kmd]

I added sodium bicarb....... all that happened was lots of fizz, but the pH remained 4.0 (pink colour)

[rae]

How much of it do you have and has it been contaminated by anything??
If not you could dilute it down and use it as stain remover for glassware.

[Graham Kemp]

Hi everyone,
I have made saturated oxalic acid (about 100mL )for a yr 11 experiment. The CSIS appendix D says it's ok to put it down the sink after making it pH: 8-10.
Could anyone please tell me which chemical I add, and how much?
Thanks heaps.
Kirin

You neutralise most acids with Sodium Carbonate; sprinkled in slowly and carefully as it will fizz and too much at a time will froth over.

In this case, it produces Disodium Oxalate and Carbon Dioxide.
H2C2O4 (aq) + Na2CO3 (s) = Na2C2O4 (aq) + H2O (l) + CO2 (g)

Sodium Bicarbonate may be used instead. It's somewhat cheeper, though not as efficient.
H2C2O4 (aq) + 2 NaHCO3 = Na2C2O4 + 2 H2O (l) + 2 CO2 (g)

Once the solution stops fizzing when you sprinkle in Sodium Carbonate or Bicarbonate, test the pH with universal indicator. It should be neutral (green). Add a little Sodium Hydroxide since you still need to raise the pH; to blue the indicator.


Do note that Disodium Oxalate is toxic. Ingestion of 10g or more is lethal. Wash to waste after a massive dilution. Mix 100mL into a bucket full of water, pour slowly into running water.

I added sodium bicarb....... all that happened was lots of fizz, but the pH remained 4.0 (pink colour)

How much oxalic acid is in your saturated solution?

For every 1.00 gram of Oxalic Acid Dihyrate you used to make the solution, you will need 1.33g of Sodium Bicarbonate (NaHCO3) to neutralise, or 0.841g of Sodium Carbonate (Na2CO3 anhydrous).

[kmd]

wow, Graham, Thanks for the information.
I've put it in a bucket of water (the saturated oxalic acid is in a 150 mL beaker, and crystalised), and have added a sprinkling of sodium carbonate. I have no idea how much oxalic acid I added, as I read that to make it saturated, you just keep adding. I suspect I had the water temp too hot, as it just kept disolving, so in the end, I added a fair bit. Is the vapour it produces while fizzing toxic too????
Anyway, will do what you've suggested. You obviously know a fair bit about all these chemicals, and so I really appreciate your advice.
Thanks heaps,
Kirin

[kmd]

Rae, thanks for your suggestions too.
Kirin

[malook]

What a shame, its great as a glassware cleaner! I hate to waste chemicals, mabey next time you do the prac.