Roger the former chemist wrote:
>As a former chemist, let me offer a few suggestions to those
>using glacial acetic acid:
[Excellent rules for home use of CH3COOH snipped....]
Bill the presently-employed-as-chemist humbly inquires:
Has any home darkroom enthusiast on the list ever used -- or ever read about
the use of -- citric acid rather than acetic acid as a stop bath? I was
just curious about this. Citric acid is certainly a lot safer to store at
home that glacial acetic acid, it's convenient in that it's a powder rather
than a liquid, it doesn't smell as bad, it's already used in a lot of
consumer products, and it's pretty cheap. A large US laboratory chemicals
supplier lists glacial acetic acid at $130 USD for 12 kg (packaged in four
3-kg glass jugs), and citric acid monohydrate at $64 USD for 5 kg (in a
plastic container). It's true that on a per-molecule basis it's about four
times as expensive as acetic acid, but it also has three times the acid
strength (three acidic groups per molecule to acetic acid's one per
molecule). That third acidic proton (the last one to be stripped off when
citric acid reacts with alkaline material) provides good buffering up to
about pH 7.4, which should be low enough to neutralize residual developer.
Probably not an economical alternative for the commercial lab, unless you
calculate in the cost of engineering controls, personal protective
equipment, environmental compliance, etc.
Just wonderin'.... Perhaps as an OT, someone on the list is going to have
to address the use of a nice dry sauvignon blanc as a stop bath, and a
full-bodied young cabernet as developer. Now there's a darkroom we can
really enjoy! :-)
Bill Peifer
Rochester, NY
-
This message is from the Pentax-Discuss Mail List. To unsubscribe,
go to http://www.pdml.net and follow the directions. Don't forget to
visit the Pentax Users' Gallery at http://pug.komkon.org.
