ferric (III) oxalate testing

[George Papantoniou]

In order to test whether the ferric oxalate is still good I have I found (in this book) there is a thing I could do: I dissolved three drops of it in 20ml of water, then added a solution (10%) of pottasium ferricyanate. If it became blue, that would mean that it was worthless.

The solution of ferric oxalate was yellow (like urine ). The potassium ferricyanate solution was also yellow. When I added the one in the other, it stayed yellow. Does this mean that my ferric oxalate is still good ?

 

[kevs]

Hi George,

The potassium ferricyanate solution was also yellow.

You need potassium ferricyanide.

Cheers,
kevs

 

[George Papantoniou]

Oh, s***... to tell you the truth, I am not really sure what it was... -ate or -ide... I'll have to check... is the one I really need (ferricyanide) NOT yellow ?
The colour of the powder I used was red, the solution made out of it quite yellow.

In high school, I was a good student... but the worst grades I ever got were in chemistry... I guess this is my punishment...

 

[doughowk]

The colour of the powder I used was red, the solution made out of it quite yellow.

Sounds like Potassium Ferricyanide.
From Dick Stevens book

Add 1 drop of the ferric oxalate solution to be tested to the ferricyanide solution. If no blue precipitate forms, the ferric oxalate is devoid of ferrous ion. If a blue precipitate appears, the ferric oxalate contains ferrous ion. If so, you must take steps to alter or remove it.
The ferrous condition can be remedied by adding small amounts of oxalic acid to the ferric oxalate

 

[George Papantoniou]

Doug, in the book I found it in the procedure of testing was described the other way round... so I added a little Ferricyanide solution in a weak solution of Ferric Oxalate (some water with three drops of Oxalate).

I'll do it the way you describe and see what happens...

 

[George Papantoniou]

Well, I did what Doug suggested and guess what... a blue precipitate formed... now I have either to order new Ferric Oxalate (from Germany) or add Oxalic acid in mine. What do you think is best ? I can find Oxalic Acid easily here in Greece. Will the result be as good as if I used freshly made Ferric (III) Oxalate ? How much Oxalic Acid should I add ?

Thanks for your help, lads...

 

[doughowk]

Since oxalic acid is used in most of the methods for making Ferric Oxalate, don't see any disadvantage from adding it to existing solution. From Dick Stevens book on Kallitypes

Add the oxalic acid 0.125 to o.25 g at a time, keeping track of how much you add. Stir the acid into the solution to make sure it dissolves thoroughly. Perform a second test in a fresh ferriccyanide solution. ... Keep adding small amounts of oxalic acid, stirring, and testing until no blue precipitate forms.

 

[George Papantoniou]

WOW!!! Thank you Doug... can you tell me if I can find your terrific book you mention (where you have found all this interesting info) ?

Now I only have to find out how to measure 0.125 g of a chemical... :confused:

 

[doughowk]

0.125 gram does seem overly precise, but that's the nature of Dick Stevens book - Making Kallitypes: A Definitive Guide published by Focal Press, 1993. Its out of print & I picked up my copy thru a BookFinder search (mine is apparently an extra copy that Phil Davis had).