Quote Originally Posted by Photo Engineer View Post
Add Ammonia? The most concentrated you can get is 28% and so that will limit you to the final concentration of Ammonium EDTA
28% Ammonium EDTA means 33% Ammonium Fe-III EDTA which is not bad at all. Note that Fuji's E6 formula calls for 12%, so whatever we can make with these primitive methods is over twice as concentrated as the final working solution.
Quote Originally Posted by Photo Engineer View Post
and how many Ammonium ions do you need? NH4EDTA, (NH4)2EDTA, (NH4)3EDTA and (NH4)4EDTA all exist. So, lets assume you want (and get) NH4EDTA, what next. It will be very dilute so you will have to purify it. Next, ow do you react it with Ferric Ion to get pure (NH4)FeEDTA. Note that the amount of Ammonium ion is really essential to balance the charge on the final ion!
Since the EDTA chelates the Ferric ion I would assume we end up with (FeIII-EDTA)- which will take on as many Ammonium ions as it has room for: one. The pH can be used to fine tune this.
Quote Originally Posted by Photo Engineer View Post
This is really a thankless task!
I could not agree more, especially if one considers that over 100g of EDTA free acid are needed for making one liter of bleach. Ideally one gets the Ammonium Ferric EDTA from a company that has the know how and the means to make it in bulk quantity and good quality. This may not always be an option for everyone, though, and the method described here might be a work around for very determined people.