Just to nitpick, not exactly. EDTA is "slightly" soluble, but has no
practical use in photography that I know of.
>One of the things EDTA
>does is scavenge oxygen; most chemicals react negatively to oxygen,
>therefore, these chemicals get a little boost from EDTA.
No way. It is a sequestering (also termed 'chelating') agent, i.e., it
establishes barriers between compounds that would normally interact and
allows each to react independently. Thus, if you try to dissolve an iron
compound with hypo in solution, you will get a precipitate; as a
sequestering agent, EDTA (one of the sodium salts, as they are extremely
soluble) prevents this so you can, for example, prepare a one solution
bleach with an iron salt and hypo. If you have an authority to quote on
that "scavenging oxygen" I'd like to have it, as one of my main areas is
sequestering agents, and I am not familiar with any such effect.
>PS: Just because
>EDTA is in some foods, DO NOT eat this stuff. Treat all chemicals with
>care, regardless of their purpose.
Last statement is very true. Even common table salt is toxic in large
quantities. But the major reason for not ingesting EDTA is that it chelates
calcium in the body and leads to calcium depletion, an unwanted condition!
In fact, when a sequestering agent is needed in pharmaceuticals, the
calcium EDTA salt is used to prevent this depletion.
This calcium sequestering effect is used in formulas designed for hard
water; the sodium EDTA prevents the calcium salts in the water from
reacting with the chemicals in the formula. It's also the reason you can
find EDTA salts in washing compounds, etc. Great stuff. But has no reaction
with oxygen that I know of.
Sil Horwitz, FPSA
Technical Editor, PSA Journal
silh@iag.net
Visit http://www.psa-photo.org/