Exposure of ferric ammonium citrate to UV light transforms the citrate ion to acetonedicarboxylic ion, this reaction being a part of the cyanotype
process: https://greenteacher.com/natural-chemistry-outdoors/
According to the link, the acetonedicarboxylic ion can undergo two more decarboxylations releasing electrons that reduce Ferric ions.
If the 2nd and 3rd decarboxylations are simply a result of thermodynamic instability of acetonedicarboxylate, and are not a result of photooxidation,
could very brief exposure to UV produce acetonedicarboxylate ion, which then could be removed as an ester or insoluble salt, before it decomposes
further? Or is the initial photooxidation not as instant and it would yield mostly citrates? Or would it be fine to let it be exposed for longer, and
the decarboxylation of the acetonedicarboxylate won't proceed as quickly as to be of concern?
[Edited on 28-5-2019 by John paul III]j_sum1 - 28-5-2019 at 17:18
Any reason for starting with FAC and not citric acid?John paul III - 29-5-2019 at 01:31
It seems easier than bubbling SO3 into concentrated H2SO4 to make oleum for the citric acid route
[Edited on 29-5-2019 by John paul III]Tsjerk - 29-5-2019 at 03:01
It also works with 96% sulfuric acid, just a bit lower yield, but both citric acid and sulfuric acid are dirt cheap. Pumukli - 29-5-2019 at 03:58
I heard that P2O5 can dehydrate even H2SO4... Maybe it would correct the yield in case you don't have
oleum. Tsjerk - 29-5-2019 at 08:15
Yes, but I wouldn't waste P2O5 to get a bit higher yield of something dirt cheap.dicyanin - 1-11-2020 at 05:15
sorry for resurrecting the dead, but I was searching for the same info and in the search enginge I found this:
Quote:
Poor man's oleum can be made by mixing sodium pyrosulfate with conc. sulfuric acid and decanting from the resulting Na2SO4. There is at least one
patent describing the process (and probably something on this forum as well).
30% oleum is used in the orgsyn process yet the SO3 function seems mainly to ensure absolutely anhydrous conditions for the oxidation. In this light
crude in situ created oleum like this seems the most ideal option, since sodium pyrosulfate is easily prepared by heating NaHSO4 above its melting
point for 4-5 hours.
Alternatively, if P2O5 works to dehydrate H2SO4, then it is likely that metaphosphoric acis "P2O5.H2O" or polyphosphoric acid "P2O5.2H2O" could also
do the job. The corresponding salts are available OTC and/or easily prepared (sodium polyphosphate ; sodium hexametaphosphate)unionised - 1-11-2020 at 05:24
