clearly_not_atara - 8-6-2016 at 12:56
http://en.wikipedia.org/wiki/Silver_phosphate
"Silver phosphate or silver orthophosphate is a light sensitive, yellow, water-insoluble chemical compound composed of silver and phosphate ions of
formula Ag3PO4."
https://books.google.com/books?id=-avSBAAAQBAJ&pg=PA104&...
"One type of phosphate glass with silver is a mixture of [...] with the addition of 8% AgPO3. The flux of radiation produces stable luminescent
centers in the glass."
Many sources indicate that Ag3PO4 and other silver phosphates are degraded by light, as is the case with other silver salts. The presumptive reaction
is:
2 Ag3PO4 + hv >> 1/2 O2 + Ag4P2O7 + 2 Ag
3 Ag4P2O7 + hv >> 3/2 O2 + 2 Ag3P3O9 + 6 Ag
2 Ag3P3O9 + hv >> 3/2 O2 + 3 P2O5 (!!!) + 6 Ag
It's possible that the reactions can also proceed in the other direction, but removing oxygen from the system (unlike the case where silver is encased
in glass) should result in the eventual reduction of all of the silver ions, leaving behind the highly sought-after P2O5.
Is it possible to produce any significant amount of P2O5 this way? Phosphorus is hard to make -- making P2O5 at STP with no toxic volatiles is a
pretty attractive proposition, and it's very surprising that it would be possible at all. Silver salts are known to be reduced by light, but some
salts are reduced extremely slowly.
AJKOER - 9-6-2016 at 07:33
With respect to the photo-decomposition of Ag3PO4, one has to avoid the presence of water or water vapor as P2O5 readily consumes H2O reforming H3PO4
and with the Ag the silver phosphate.
So, you we need an appropriate solvent that blocks water vapor and allows good uv exposure.
If you manage to accomplish that, even if the reaction is very slow, you may then consider investing in an appropriate UV lamp (which may increase
your yield 10 fold).
The photolysis of silver compounds is quite exciting as the photolysis of aqueous a silver salt can form Ag+ and a solvated electron e-(aq), which may
recombine creating elemental Silver or Ag(0). Further, flash photolysis of the latter can reform Ag+ and the solvated electron (source: see "Hydrated
Electrons Formed in the Flash Photolysis of Ag° and Tl° ", available at https://www.google.com/url?sa=t&source=web&rct=j&... ).
Interestingly, the action of O2 with e-(aq) under photolysis could also form the superoxide radical anion, .O2- (see Wikipedia comments at: https://en.m.wikipedia.org/wiki/Solvated_electron and also 'Ecology of Humic Substances in Freshwaters: Determinants from Geochemistry ...' by
Christian Steinberg, p. 152, Figure 5.14 ). The presence .O2-, per your Wikipedia reference on Ag3PO4, was also cited from the photolysis of Ag3PO4.
Cool stuff!
[Edit] Found a related work, "Photolysis of polyphosphate ions in alkaline aqueous solution", by Monica Gonzalez, available at: https://www.academia.edu/13375918/Photolysis_of_polyphosphat... . To quote:
"Photolysis of phosphate and pyrophosphate ions inaqueous solution was reported to yield reactive solvated electrons and phosphorus-containing
radicals as the primary photochemical reactions [1], as shown inreaction (1) for pyrophosphate ions"
[Edited on 10-6-2016 by AJKOER]
clearly_not_atara - 10-6-2016 at 16:41
Would Fluorinert be a good idea? It seems like the safest possibility, since the reaction intermediates are hella oxidizing (O2-* and possibly 1O2). I
don't know how easy it is to dry.
It also seems like you could save on 2/3 of the work by making silver metaphosphate directly from sodium metaphosphate and silver nitrate, although
the nitrate is dangerous to make, so maybe the sulfate (which has low but appreciable solubility) could work.