Re: Potassium Oxalate

Sandy,
By using your recipe you have a fair excess of oxalic acid (about 17%),
which is not that soluble. You can add some more potassium carbonate (as I
noted, 10 maybe even 15 grams) and still have about 5% excess oxalic acid.
Typical POTA solution should be on the acidic side.
By adding some sodium carbonate you have created mixture of potassium and
sodium oxalate, with really a small amount of sodium, inconsequential for
Pd development (that would be my guess, I have not tried that trick yet).
Sodium oxalate is not very soluble, especially in cold solution. If you
have added more then a few grams it might crystallize from the solution.
Marek
>
> I separated the clear potassium oxalate solution
> from the undissolved stuff at the bottom and put
> it aside. I then added about 100 gs of water to
> the undissolved junk and stirred. But it still
> did not dissolve, so I then added some sodium
> carbonate (by mistake since I meant to add
> potassium carbonate). There was a lot of fizzing
> and when it stopped everything was in solution.
> But what do I have? Sodium Oxalate, or a mixture
> of sodium and potassium oxalate?
>
>
>
> Sandy
>
>
>
>
>>I used the anhydrous variety of potassium carbonate.
>>
>>Thanks for the information about concentration.
>>I will add some water to the solution and see if
>>the stuff at at bottom dissolves.
>>
>>Sandy
>>
>>
>>
>>>Sandy,
>>>What form of potassium carbonate did you use? If it is anhydrous, then
>>> you
>>>are about right, you can still add another few grams of potassium
>>>carbonate, say 10 grams. If you used hydrated potassium carbonate, then
>>>your proportions are off. By my estimation your solution is about 1.0M.
>>> I
>>>don't find any benefits using solutions more concentrated then 0.9M (im
>>> my
>>>practice, pritning Pd), so you can add some water to it (50-100cc).
>>>You should not have any undissolved stuff.
>>>Marek Matusz
>>>
>>>> I mixed up a solution of potassium oxalate
>>>> following directions provided by Nzé Christian. I
>>>> added 130 gs of oxalic acid to 500 ml of water,
>>>> mixed until dissolved, and then added 100 gs of
>>>> potassium carbonate, and finished by adding
>>>> another 15 gs of potassium carbonate, and finally
>>>> I topped off the solution to one liter. Distilled
>>>> water was used.
>>>>
>>>> The solution works fine for printing but there is
>>>> still some junk at the bottom of the container
>>>> that has not dissolved. What did I do wrong? Do I
>>>> need to add more water, increase the temperature
>>>> of the mix, or other?
>>>>
>>>> Sandy King
>
>
Received on Wed Sep 15 15:26:00 2004