The recipe itself is a little indeterminate in that it suggests adding 50 ml of
30% H2O2 to the ferrous oxalate a ml at a time as the reaction is violent. The
mixture certainly gets very excited but it was a little disconcerting to
discover that one had to add 500 ml a ml at a time to the sputtering liquid to
make it work, not 50 ml.
The first batch was made in 1994,
I have now made three more batches in the same way as I did in 1994 but two of
them used 20 vol rather than 30 % H2O2. All three batches finished up with a
sediment rather than green charteuse coloured ferric oxalate solution. But by
adding large amounts, of oxalic acid to the beakers which contained from 600 to
1000 ml of root beer coloured liquid, and the sediment, and stirring, all three
batches were made to turn ferric oxalate green.
I now had three lots of oxalate of different strengths plus the original 1994
batch.
I have just tested them by coating one piece of paper with enough solution from
each batch, with pd, for a step wedge. The paper was exposed under a UV lamp
for twenty minutes. All recent batches exposed to between steps six and seven
on the step wedge and the 1994 batch to between steps 4 and five.
All developed out to between 15 and 16 including the 1994 batch.
The recipe from which I was working gave the ingredients in pounds and the
instructions in metric to tenths of a gram.
Terry King