[Alt-photo] Cyanotype chemistry question

Keith Schreiber keith at jkschreiber.com
Sat Jan 25 21:13:12 UTC 2020


Hi Chris,

As I mentioned in my previous post, they do NOT have the same CAS numbers.

Ferric ammonium oxalate trihydrate — (NH4)3[Fe(C2O4)3]*3H2O — CAS #13268-42-3
Ferric ammonium oxalate — C6H12FeN3O12 — CAS #14221-47-7
Keith Schreiber, Taos NM


> On Jan 25, 2020, at 1:55 PM, Chris Seiberling via Alt-photo-process-list <alt-photo-process-list at lists.altphotolist.org> wrote:
> 
> Thanks! I see that both have the same CAS Number. It’s curious to me that it’s possible to buy both of them even if they’re the same, chemically.
> 
> Chris Seiberling, Sharon MA
> 
>> On Jan 25, 2020, at 2:18 PM, Kelcy Patterson <jimbobnola at cox.net> wrote:
>> 
>> Hi, the first formula is grouped by ions: NH4 = ammonium ion, Fe = ferric (iron III) ion, C2O4 = oxalate ion, with .3H2O being 3 waters of hydration.
>> 
>> The second formula is grouped by total elements. It is the same, minus the 3 waters of hydration.
>> 
>> Jim Patterson, New Orleans
>>> On January 25, 2020 at 11:27 AM Chris Seiberling via Alt-photo-process-list <alt-photo-process-list at lists.altphotolist.org <mailto:alt-photo-process-list at lists.altphotolist.org>> wrote:
>>> 
>>> 
>>> Hello photographic chemists (and others):
>>> 
>>> Mike Ware's 'New' Cyanotype calls for Ammonium iron(III) oxalate-- (NH4)3[Fe(C2O4)3].3H2O. He says this is also known as ferric ammonium oxalate. But I understand ferric ammonium oxalate's formula to be C6H12FeN3O12 ? Is there a practical difference? I’m not enough of a chemist to understand the formulaic implications. 
>>> 
>>> Thanks, Chris Seiberling
>>> 
>>> 
>>> 
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> 
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