[alt-photo] Re: Ammonium Citrate

[etienne garbaux]

Jon wrote:

>Is Ammonium Ferric Citrate the same as Ammonium Citrate?

No.  Ammonium Ferric Citrate (better known to us older folks as 
Ferric Ammonium Citrate or FAC), C6H8O7.nFe.nH3N, is CAS No. 
1185-57-5.  Ammonium Citrate, (NH4)2C6H6O7, is CAS No. 3012-65-5.

The "n"s in the FAC formula indicate that FAC can have varying 
amounts of Fe and NH3.  The green form (lower Fe and NH3, higher 
hydrated citric acid) is generally preferred for photographic uses.

Best regards,

etienne