I'll leave Mike Ware to comment on his work on this, but you might like
to know that the recipes using ferric oxalate prepared in solution
solution - at least 3 on this list including mine in the past few months
- work without problems. (I have used this in various methods - the
silver solution either in the sensitizer or the developer.)
At least one 'traditional' recipe quoted (for example) in the Keepers of
Light - William Crawford calls it the Van Dyke Process - uses ferric
ammonium citrate. In case you haven't got the book handy:
A: 9 g ferric ammonium citrate in 33ml distilled water
B: 1.5 g tartaric acid in 33ml distilled water
C: 3.8g silver nitrate in 33ml water
Mix A+B, then add C slowly with stirring. Coat and expose normally.
Develop in running water, fix with 5% plain hypo. Wash, gold tone if
required.
Peter Marshall