From a purely practical and economic perspective making Ferric Oxalate for pt/pd printing is not worth the trouble IMHO. Even the method described on jeffrey mathias website, which Jorge describes as far easier than the traditional method, takes many, many hours to complete, and in the end yields only about 125g of ferric oxalate powder.
And, compared to the costs of the platinum or palladium salts, feric oxalate represents a very small investment in the overall cost of pt/pd printing. A hundred grams of ferric oxalate from Artcraft costs $50, enough to make over 400ml of the working 25% ferric oxalate solution used in Pt/Pd printing. By contrast, an equal amount of 20% palladium or platinum solution (based on prices at B&S) will cost between $800-1400.
Sorry for the me too, but Sandy and Ed are right.... spend
time making prints not chemistry....I once had the pleasure in watching Sullivan make chemisrty.....some thing about the smell of almonds that cleared the lab...
Life is to short to cut corners....I have found that with
B&S if something is not rite they make it rite.
I think that a good shortcut could be had by eliminating the step of isolating the ferric oxolate. You could simply add oxolic acid, ferric nitrate, and the right amount of sodium hydroxide to your working solution. As long as the residual sodium nitrate doesn't interfere with the developing, you should be in good shape.
As others have mentioned you are making a platinum print, not ferric oxalate. I see no reason to isolate it.