What can I substitude for disodium phosphate? (Bleach)

[Athiril]

looking to try out a ferricyanide bleach formula

it contains 6.8 grams of disodium phosphate, its one chemical i cant find at the store in Australia that sells most of this stuff (or under any of its other names), no phosphates at all.

As far as EDTA goes, the shop sells EDTA tetra sodium salt and EDTA acid, there is no premixed Ammonium Ferric EDTA

And the shop also only sells Ferric Ammonia Citrate and Ferric Ammonium Citrate.

Given a combination of these, I don't know if it's possible to make an effective bleach out of those?




Otherwise my last choice looks like copper sulphate + sodium chloride, as I don't like the idea of messing with dichromate as per my previous thread.

In case its important, this is the recipe I was going to follow.
Water 100F 750ml
Pot. Ferricyanide 90g
Pot. Bromide 20g
diSodium Phosphate 6.8g
Sod. Thiocyanate 5% soln. 90ml
Water to make 1 litre

The other formula is:
Potassium ferricyanide 80.0 g
Potassium bromide 20.0 g
Disodium phosphate, anhydrous 12.0 g
Acetic acid, glacial 5.0 ml
Water to 1.0 litre

 

[Athiril]

scratch that.. quinone looks bad

 

[Mike Wilde]

While the postage will be a factor, look up jd photochem. Claire ships all over the world. I use your first bleach formula, but in a simpler form; 80g K Ferri, 20g K Br per litre. At 38C it bleaches c-41 in 2.5 minutes. I replenish 45mL of stock into working per 80 sq in of flim., and when the 'replenisher' is usd up I take the overflown and the used up working solution contents to the HHW site for disposal. It might go further, but I don't risk it.

 

[cinejerk]

I agree. I can find this chemical either. Is there a more common name or use for this stuff?

 

[Photo Engineer]

The Disodium Phosphate is there as a buffer. The unfortunate problem is that the pH is not recorded with the formula, otherwise I could suggest an alternative. Sodium Carbonate might work, but IDK what to aim for to get to the right pH. It is not an active part of the bleach and so you might just mix some up without it and see what happens in a test.

Many photographic formulas like this leave one hanging in this sense though if modifications or substitutions must be made. Sorry.

PE

 

[cinejerk]

Yes, I couldn't find a final ph for any of the bleach formulae I have either. But I did find this on
my bottle or ranch salad dressing: Disodium Phosphate - additive used as an emulsifier. Also increases shelf life.

 

[Photo Engineer]

Sorry, use of food grade chemistry in photography is not my area of expertise!

Seriously, Disodium Phosphate has and has had many uses. A common use was a buffer in laundry washes. I believe that you can find it also as Disodium Hydrogen Phosphate. It is Na2HPO4. You can prepare it from TSP, Trisodium Phosphate (Na3PO4) by adding acid or from Sodium Dihydrogen Phosphate by adding base (NaH2PO4). TSP is a cleaning agent used in many strong cleaners.

I don't recommend this bleach, nor the use of strong cleaners. I suggest you just leave it out. Most Ferri bleaches don't use it anyhow.

PE

 

[cinejerk]

Every formula I have for e6 bleach using potassium ferricyanide has disodium phosphate in it???

What e6 bleach do you recommend?

 

[mts]

I use persulfate-quinone bleach for E-6 with good success. Why do you comment that quinone "looks bad?" PE correctly cautions that there is a risk of toxicity, but I haven't found that to be a problem, at least for use in small tanks. See the alternative E-6 thread for more discussion.

 

[cinejerk]

mts can you list a formula for your quinone bleach or provide a link to the alternative e-6 thread?

 

[Photo Engineer]

The phosphate is a buffer, but if you wish you can leave it out for a one shot after a few tests to determine the proper pH value. I suggest starting at about 5.5. If there is stain, add about 5 g/l of Disodium EDTA.

MTS is right though. The quinone bleach is not that bad. They used to make green ink out of quinone.

PE