That's not the same as Ferric Ammonium EDTA that is used in Blix. For reasons that escape me, that is now only available in liquid form.
Originally Posted by eclarke
You cited EDTA in your post and the response was perfectly valid based on that.
There is EDTA solid, Disodium EDTA solid, Tetra Sodium EDTA solid and Sodium Ferric EDTA solid.
Then there is Ammoniium Ferric EDTA which is either solid (VERY expensive) or liquid (moderately expensive).
All are used in photography, and you can make the Ferric salts from EDTA.
Hi PE: My bad for not realizing I had not referenced Na Fe EDTA in my prior post. Sorry eclarke - you were correct to point out what is available at Artcraft.
PE, in a prior post (I don't have it to hand but looked at it this afternoon) you indicated that it would be difficult to remove to sodium ion if starting with one of the sodium EDTA variants. If there is a particular (inexpensive) EDTA one can start with to make the ferric salt from, I am sure several here (including me) would be interested to know what to do.
Also - Any idea why solid Na Fe EDTA has become so expensive? I still have 2LB of it that I bought from Rayco (no longer in existence) when I was living in England in the late '80's/early '90's. It was pretty cheap then. Is this another example of the enviro police driving us away from chemical industries and toward a digital utopia?
Yes, you can get plain EDTA, the free acid form. You then carefully neutralize it with Ammonium Hydroxide and then you add Ferric Bromide or the like. You end up with Ferric Ammonium EDTA and Ammonium Bromide which is a good bleach or the starting point for a good blix!
You have to be careful, as the reactions are sometimes strong, and sometimes result in dilute solutions. I've done it in the lab though, albeit about in 1966 last. After than, EK had the liquid available internally.
Another route is possible, but not to us folk. It takes a full lab.
I recall from the other thread that the other route may involve ammonia gas and high pressures? We can skip that.
Are there other iron salts that could be used? I suspect that Ferric Bromide is not the cheapest.
It seems I have 100g of EDTA acid - also from Rayco - it might be fun to do an experiment.
By the way -- I assume that ferricyanide bleach may be out of the question for RA4 as it would discolor the paper?
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threads like this remind me how in danger color ( colour ) imaging is.
who knows how long the chemistry will be available for, and at what price ...
for reasons like this i will stick to coffee and soda and vit c and if i ever need color
i will do tri color work ... maybe i should buy 100LB of thiosulphate to make sure in my kids
lifetime if they ever want to do chemical based photography, they can ...
thanks for the wake up call!
John if you do that, make sure it's anhydrous -- the crystalline version, used at about 12oz/litre, wouldn't last as long as you think! Or just buy more.
You can buy dry fixer chemistry, which is basically sod. thiosulfate anhydrous and sodium metabisulfite, a 1 gallon mix, for about $5. That's what I plan to stockpile, unless PE tells me such a mix is not stable!
Yes, there is another route, and that is what I referred to in my last post. It involves lab scale work with high tech equipment.
Also, Hypo goes bad with keeping! Even solid hypo goes bad.
PE to make bleach as you described, could one use ferric chloride instead of ferric bromide? It seems to be much cheaper. Or ferric ammonium sulfate.
Sodium thiosulphate has other uses in chemistry and medicine, so it's likely to be around for a while yet. One thing in B&W photography, they didn't develop new chemicals to make it work, they took existing chemicals and saw which ones would work.
Originally Posted by jnanian
See my Blog at http://clickandspin.blogspot.com
The greatest advance in photography in the last 100 years is not digital, it's odourless stop bath....