substitute for nitric acid?

[Marco Buonocore]

Is there a substitute for nitric acid?

I've used sodium bisulfate as a substitute for sulfuric acid; I'm looking for something similar.

I use 15ml of nitric acid in a litre of bleach for the B3 bleach in the Dupont Varigam toner system. I would love to have a powder I could mix in as I'm not all that comfortable with strong acids.

thank you!

 

[keithwms]

What's the purpose of the nitric in this formula? Can you post the whole formula? If we know what it's meant to do we can probably suggest a substitute. If it's just to oxidize something then...

For safety, what most of us do, who work with acids, is make a much weaker "x" molar solution and work with that.

 

[Marco Buonocore]

Keith,

It's a bleach from the Defender / Dupont varigam toner system. . they are thiocarbamide sepia Toners.

the formula:

bleach B3

to make 1l
22g potassium ferricyanide
35g sodium chloride
15ml nitric sciences

 

[Leigh Youdale]

I always found concentrated nitric was very good for burning off warts. You have to be careful though! Use a glass straw, very small droplets, avoid breathing the fumes while it dries and if the underlying skin gets very red and sore, stop using the nitric for a few days. Just sayin'

 

[keithwms]

Well, okay, 15mL of nitric in 1 L of water is what, a ~200 mM solution? So you just make up a big bottle of that, which will be safer to work with, then you don't have to work with the concentrated stuff anymore.

You can check the math...

http://www.lgpnet.com/science/molarity.htm

 

[ME Super]

If you get the nitric acid on your skin, it'll turn it a shade of highlighter yellow. My college chemistry prof called this "dinitroskin." Apparently the nitric acid reacts with an amino acid in your skin and produces a yellow dye. If it's left on long enough, the top layer becomes less skin-like and more paper-like.

ME Super

 

[Marco Buonocore]

Regarding the yellow: I wonder if there's not a similar amino acid in the gelatin in photo paper, because prints bleached in the B3 bath go very much that highlighter colour. Must brighter and more difficult to wash off than just plain ferricyanide.

Keith: Thank you for the advice, that website will do the trick nicely!

 

[Rudeofus]

From looking at it, this is just a rehalogenating bleach. I've seen plenty of recipes out there. It might be worthwhile to try one of these and see what happens.

 

[Athiril]

Well, okay, 15mL of nitric in 1 L of water is what, a ~200 mM solution? So you just make up a big bottle of that, which will be safer to work with, then you don't have to work with the concentrated stuff anymore.

You can check the math...

http://www.lgpnet.com/science/molarity.htm

In regards to dilution, do not add concentrated acid to potassium ferricyanide solution, unless you enjoy breathing hydrogen cyanide gas.

Keith,

It's a bleach from the Defender / Dupont varigam toner system. . they are thiocarbamide sepia Toners.

the formula:

bleach B3

to make 1l
22g potassium ferricyanide
35g sodium chloride
15ml nitric sciences

nitric sciences??

 

[Photo Engineer]

I would think that that bleach would cause loss of highlight detail, due to the formation of AgCl and then the reverse reaction with the formation of AgNO3. This type of rehal bleach was abandoned due to that type of problem.

Just a thought for you all. It is a possibility due to the kinetics of the reaction.

PE

 

[Ian Grant]

Agfa published 4 different re-halogenating bleaches for toning along with 4 toners, these could be used in any combination to give a wide variety of tones.

You might try adding 20 gms of Sodium Carbonate or 10ml of Ammonia to a Frerricyanide/Potassium Bromide bleach or a Ferricyanide/Sodium Chloride bleach as both will give different tones.

Ian

 

[Kirk Keyes]

I would think that that bleach would cause loss of highlight detail, due to the formation of AgCl and then the reverse reaction with the formation of AgNO3. This type of rehal bleach was abandoned due to that type of problem.

Perhaps hydrochloric would be a good substitute - it will make the solution acidic, and add more chloride ions and not nitrate ions so there would be no conversion to silver nitrate.

I've read that the yellow compound formed when you get nitric on your skin is related to picric acid.

 

[keithwms]

That's an excellent suggestion from Kirk. I also imagine that there'd be less issue of aging with hydrochloric- it'd store better than the nitric.

 

[Photo Engineer]

Kirk has a good suggestion for adding acid and for preventing solution of the detail.

IDK what the yellow is, but I have seen it too. Too many times! But, it peels off.

PE

 

[Rudeofus]

Hydrochloric acid is about as inconvenient as nitric acid for home users, remember that HCl is a gas which tends to escape from the water it is dissolved in, and a bottle of strong acid doesn't blend well with the average house hold. There is no nitric acid equivalent to bisulfate, but if the action of the nitrate ion is not needed, sodium bisulfate would be the most convenient chemical to lower the pH value of your bleach. IIRC, it is a solid used in large quantities to lower the pH of swimming pools, so it should be readily available.

 

[Ian Grant]

Perhaps hydrochloric would be a good substitute - it will make the solution acidic, and add more chloride ions and not nitrate ions so there would be no conversion to silver nitrate.

I've read that the yellow compound formed when you get nitric on your skin is related to picric acid.

The Nitric acid is there to control the size of the grain, the finer the grain the warmer the tone, so in that respect Hydrochloric acid isn't a substitute. Ammonia will also control the grain size which is why Agfa use it in Agfa 502 Bleach.

Another possibility is to use Ammonium Chloride instead of Sodium Chloride in the bleach.

Ian

 

[Rudeofus]

The Nitric acid is there to control the size of the grain

Would it really do that if such an overabundance of chloride is around? And if it really did, wouldn't bisulfate do the same thing? AFAIK, b&w reversal bleach uses bisulfate plus an oxidizer for this reason.

 

[Ian Grant]

Would it really do that if such an overabundance of chloride is around? And if it really did, wouldn't bisulfate do the same thing? AFAIK, b&w reversal bleach uses bisulfate plus an oxidizer for this reason.

Well if you leave it out the tones aren't the same so it must play a part in the re-halogenation process. If the nitric acid dissolves some silver it would then be converted to Silver Chloride but effectively giving finer grain.

Ian

 

[Photo Engineer]

Bisulfate in this bleach can cause problems. You see, it forms Sulfate and Silver Sulfate can then form during the bleach. It turns out that Silver Sulfate is also quite soluble and therefore can remove some Silver image permanently.

PE

 

[Rudeofus]

Bisulfate in this bleach can cause problems. You see, it forms Sulfate and Silver Sulfate can then form during the bleach. It turns out that Silver Sulfate is also quite soluble and therefore can remove some Silver image permanently.

And in this fact it is very similar to nitric acid, that's exactly why I suggested it as replacement. You seem to prove my point here. Compared to nitric acid, bisulfite is a much nicer substance to store outside of a lab environment, too, and you can buy it without getting the strange "what is he going to blow up with this?" look.

@Ian: Note that the difference between 6B-3 and the other two bleaches is not only the nitric acid but also the halide used for rehal.

 

[Ian Grant]

@Ian: Note that the difference between 6B-3 and the other two bleaches is not only the nitric acid but also the halide used for rehal.

Yes. I had realised that. I did try the bleaches in this toner in the late 1970's when I was working on Toners commercially. I particularly liked the chloride based bleaches for their more yellowy/orange tones.

It's often not realised that the developer used initially can also affect the final image colour after toning.

Ian

 

[Rudeofus]

Yes. I had realised that. I did try the bleaches in this toner in the late 1970's when I was working on Toners commercially. I particularly liked the chloride based bleaches for their more yellowy/orange tones.

There was a thread here some time ago about chloride rehal bleach and the consensus was that chloride bleach killed the highlights in a print. Is this problem still there or was there some solution to this? Or maybe the nitric acid is the solution?

 

[Ian Grant]

There was a thread here some time ago about chloride rehal bleach and the consensus was that chloride bleach killed the highlights in a print. Is this problem still there or was there some solution to this? Or maybe the nitric acid is the solution?

It's not so much that any bleach / toner kills the highlights rather that the overall Dmax of a very warm toned yellow/brown print has a very significant drop in density across all the tones.

If you redevelop a print bleached in a simple rerricyanide/chloride or ferricyanide/bromide based bleach it should return to the same density, hover add something like Nitric acid, Ammomia maybe as you suggest Bisulphate then you interfer with the simple rehalogenation process adding the pprobability that some silver is dissolved may diffuse slightly in the print emulsion before being converted to halide again, this gives the finer grain whin in turn results in warmer tones.

Remember that another variable in bleaches is the excess or lack of excess of the halide, so Agfa 500 uses a ratio of 15:1 Ferricyanide to Bromide while 501 uses a 5:1 ration (ratios by weight). If there's no excess of halide in the bleach then Silver Ferricyanide complexes are formed which are less stable and will reduce theeffects of the subsequent toner.

In this case the ratio is closer to the 1:1 used in a typical Bleach such as used in Ilford IT-1or Kodak T-52 & T-56, so great excess of halide but with a silver solvent present.

Because of the overall density loss many toners require over exposer at the printing stage to compensate.

Ian

 

[Photo Engineer]

There was a thread here some time ago about chloride rehal bleach and the consensus was that chloride bleach killed the highlights in a print. Is this problem still there or was there some solution to this? Or maybe the nitric acid is the solution?

I am afraid that the use of a Chloride rehal bleach can lead to loss of highlight detail due to dissolution of the resulting AgCl. Some AgNO3 will also form in this particular bleach thus increasing loss of Ag. This should be noticeable in the final prints, but the toning may obscure it.

PE

 

[Gerald C Koch]

Nitric acid reacts with certain proteins to form yellow nitrated products. This reaction is known as the xanthoproteic reaction. This test is carried out by adding concentrated nitric acid to the substance being tested. If proteins that contain amino acids with aromatic rings are present, the mixture turns yellow. Upon adding a strong base such as liquid ammonia, the color turns orange. These color changes are caused by nitrated aromatic rings in the protein. This is a common chemical test that is often used in biology classes, ie to show that cooked egg white contains protein.

Of the three concentrated acids found in chem labs hydrochloric acid produces an immediate stinging or burning sensation. With nitric acid one often does not even know that there was skin contact until the next day when the yellow color appears. The oil in the skin provides some protection against sulfuric acid. After contact one can walk slowly to the sink to wash it off and never be burned, A woman student in a lab I was in fumbled a bottle of conc sulfuric acid all over herself. She was immediately put under the safety shower. Her clothes were destroyed but she suffered no burns.