[aeacfm]

How to prepare a 5-6 % Sodium oxalate soln the solubility is 3.7 g/100ml , after boiling the solid crystallizes again , the same happen when adding HCl ? any ideas 

[Borek]

You can't prepare a solution with the concentration higher than the solubility.

[Arkcon]

Like Borek: said, it doesn't seem possible.  Why do you need this solution?  Are you mis-reading a protocol in some way?  If I Google for solutions of sodium oxalate, I can see that Sigma-Aldrich sells a volumetric standard at 25g per liter.  And I did find this ancient protocol here: {click}.but I think that one uses a decimal that centered, for some reason:  i.e. 0.5 % written as ·5 %.

[EDIT]

All references to sodium oxalate in the USP, as an example, specify a lower level.

[aeacfm]

Arkon , good point but i think i am sur eof the number the soln is 0.5 M Oxalate .

its  0.5 M Oxalate soln , i will use it as a catalyst or synergist with 0.5 M EDTA soln , to be used as a solvent.

[Dan]

You say in your second post that you need 0.5 M oxalate, so does this mean you don't need sodium? Potassium oxalate is quite a lot more soluble than sodium oxalate.

[aeacfm]

unfortunately , i only have the sodium salt in the lab

[Dan]

unfortunately , i only have the sodium salt in the lab

And unfortunately we only have the laws of nature in this universe... you can't make 0.5 M sodium oxalate at room temperature, it isn't soluble enough.

[Arkcon]

How to prepare a 5-6 % Sodium oxalate soln the solubility is 3.7 g/100ml , after boiling the solid crystallizes again , the same happen when adding HCl ? any ideas

Arkon , good point but i think i am sur eof the number the soln is 0.5 M Oxalate .

its  0.5 M Oxalate soln , i will use it as a catalyst or synergist with 0.5 M EDTA soln , to be used as a solvent.

0.5 M ≠ 5% for sodium oxalate in water.

[aeacfm]

And unfortunately we only have the laws of nature in this universe... you can't make 0.5 M sodium oxalate at room temperature, it isn't soluble enough.

Never mind.
I found it prepared in US  Number: 5,259,980 , so wondering how to make it as its not indicated in detail.

Arkon , good point but i think i am sur eof the number the soln is 0.5 M Oxalate .

its  0.5 M Oxalate soln , i will use it as a catalyst or synergist with 0.5 M EDTA soln , to be used as a solvent.

0.5 M ≠ 5% for sodium oxalate in water.
[/quote]

if my calculations are right i  think its bigger =  6.7 % , but i am going through 5% only as i don't have much of the salt for more of trials.