How Safe Is Potassium Ferricyanide?

[dancqu]

I'm about to make up a solution of the chemical.
I know that it is rather commonly used in darkroom.
Have I missed any or some specific precaution one
should be aware of? Also, what of it's solubility
in water? Dan

 

[removed-user-1]

I'm no chemist, but here is an MSDS on the compound: http://www.jtbaker.com/msds/englishhtml/p5752.htm

 

[Vaughn]

As one can read from the MSDS, it is not very dangerous stuff, and when handled with normal care that one should have with all chemicals, safe to use. The cyanide is tied tightly with the iron, I believe, thus will not cause death like cyanide will. Beware of mixing with strong acids, and don't heat it up, and you'll be right. The MSDS said to keep it away from Ammonia, which I had not heard of before...interesting.

I don't believe any formulas ask for it to be mixed in a saturated solution, so you will find that it mixes easily with water at any dilutions required. It will mix easily with cool water (one does not have to use warm water.)

Vaughn

 

[Kirk Keyes]

Vaughn has pretty much covered it. I'll second the part about the cyanide being tightly complexed with the iron. I have tested more water samples than I want to remember for cyanides of various forms, and boiling ferricyanide at pH of 4.5 will not liberate the cyanide from the complex. Boiling it with a pH of about 2 or less will. So as long as you don't expose it to low pH it is very safe.

Here's an anecdotal story I was told by a chemical engineer from Intel several years ago. Some guy decided to commit suicide and he figured ingesting potassium ferricyanide would be a good way to do it. Appearantly, he was not getting any reaction from the small amounts that he had initially ingested, and eventually swallowed nearly a pound of the ferricyanide. Well, of course, his stomach acid was not strong enough to liberate the cyanide, but the ferricyande overworked this kidneys and put such a tax on his system, that he did die. But it took days and was much more painful than he had hoped... At least that's what the engineer told me.

 

[aluk]

As noted above, it is unlikely that you will be harmed by it in the course of your photography work. That being said, the Kodak MSDS informs us that "contact with acids liberates hydrogen cyanide" a.k.a. Zykon B.....so use it, but with prudence (which of course is the case with most darkroom chemicals).

 

[dancqu]

The MSDS said to keep it away from Ammonia, which
I had not heard of before...interesting. Vaughn

Ferricyanide is a strong oxidizer. A reaction similar to that
of chloride bleach + ammonium hydroxide may occur.
With ammonium fixer there should be no problem.
Thiosulfate itself is a mild reducing agent.

I've no strong acids about. Will be careful. About to
introduce myself to latent image bleaching. Dan

 

[Justin Maramba]

Don't mix with stop bath.

 

[Ian Grant]

As has been said Ferricyanide is only a mild poison, so normal darkroom precautions are sufficient, but it can be potentially fatal if it's accidentally mixed with a strong acid ans Hydrogen Cyanide gas can be liberated.

Ian

 

[Kirk Keyes]

Don't mix with stop bath.

Most stop baths do not qualify as strong acid, unless you are using sulfuric acid solution at low pH - and why are you trying that anyway?

 

[Kirk Keyes]

I've no strong acids about. Will be careful. About to
introduce myself to latent image bleaching. Dan

It's quite safe when used for bleaches.

 

[Claire Senft]

well I would also, Mr keyes beware of glacial acetic acid.

 

[Kirk Keyes]

Glacial Acetic Acid is not a strong acid, as the term "strong acid" is used by chemists.

 

[Ian Grant]

Regardless of its strength I still wouldn't add Glacial Acetic acid to Ferricyanide. I worked extensively with Cyanides for about 20 years, personally I took greater precautions than most others because of my biological sciences training/background. A colleague had found his best friend dead in a toilet at work after he committing suicide by drinking cyanide, he said it was a horrific death.

Despite knowing Ferricyanide is only mildly poisonous I still use double washing techniques after using it, out of habit I guess.

Ian

 

[Photo Engineer]

Glacial Acetic acid is an organic acid and as such can cause considerable burns quickly if not washed off. Admittedly, Sulfuric Acid is much worse, but I wouldn't dismiss Acetic acid and the harm it can do. A splash in the eye is particularly bad.

Ferricyanide's toxicity is quite overblown. You just about have to boil it with strong acid to release HCN, but.... In strong daylight in ponds or other effluents, the HCN is released slowly as part of the COD and BOD and is toxic to fish and other aquatic life. We ran a study on this at Kodak and it is part of the reason we converted to Ferric EDTA in the late 60s.

PE

 

[Ian Grant]

Ferricyanide's toxicity is quite overblown. You just about have to boil it with strong acid to release HCN, but....

PE

Which exactly what could happens if you were to pour concentrated Sulphuric acid into a Ferricyanide solution . . . You wouldn't be posting on APUG again.

Ian

 

[Photo Engineer]

Then you would catch up to me in the number of posts.

I don't use conc Sulfuric acid Ian. I have not for years for just that reason among a host of others.

The strongest I use is about 35% Sulfuric and the same for alkali. I try to keep a series of balanced concentratins of acids and bases on the shelf for easy neutralization or pH shifting. AAMOF, I just finished making a new Tetra Aza Indene solution using dilute acid and base.

PE

 

[pentaxuser]

About to
introduce myself to latent image bleaching. Dan

I saw the effect of this in a series of prints in Tim Rudman's book. Amazing and it sounded quite simple.

Let us all know how it goes. Thanks

pentaxuser

 

[Vaughn]

Glacial Acetic acid is an organic acid and as such can cause considerable burns quickly if not washed off...
PE

I can confirm this -- I spilt some Kodak Indicator Stop Bath Concentrate over the back of my hand -- immediately I washed it off. Ended up what looked like a very mild sunburn on my hand. I'd hate to think what would happen if I got in my eyes!

Vaughn

 

[Anscojohn]

I'm about to make up a solution of the chemical.
I know that it is rather commonly used in darkroom.
Have I missed any or some specific precaution one
should be aware of? Also, what of it's solubility
in water? Dan

******
Heed the note about the strong acids. Hydrogen Cyanide, aka Zyklon B, was used to kill people in the Nazi gas chambers.

 

[Sirius Glass]

I can confirm this -- I spilt some Kodak Indicator Stop Bath Concentrate over the back of my hand -- immediately I washed it off. Ended up what looked like a very mild sunburn on my hand. I'd hate to think what would happen if I got in my eyes!

Vaughn

Vaughn,

Was this an accident or are you conducting experiments based on what you read in the APUG posts? :confused:

Steve

 

[Larry Bullis]

Glacial Acetic acid is an organic acid and as such can cause considerable burns quickly if not washed off. ...
PE

I worked with someone who had lost his sense of smell. After he returned from his service in the marines during the Korean War, he went to school on the GI bill. He dropped a glass gallon jug of glacial acetic acid in a light trap, and they made him clean it up. I asked him how he felt about losing his ability to not only just smell, but to enjoy the subtle flavors of sole with lemon sauce - we were having dinner when the conversation occurred.

His answer: "Well, it was MY fault!"

 

[Photo Engineer]

I can confirm this -- I spilt some Kodak Indicator Stop Bath Concentrate over the back of my hand -- immediately I washed it off. Ended up what looked like a very mild sunburn on my hand. I'd hate to think what would happen if I got in my eyes!

Vaughn

Vaughn;

Actually, a large part of the red color was probably the indicator dye in the Kodak Indicator Stop Bath. It is easily mordanted to skin and can stain it.

PE

 

[Photo Engineer]

When I was teaching Organic Chem Lab 301, a young gal was shaving sodium metal under benzene. She decided to pour the scraps down the sink and wash it away with water. I was running towards her screaming NONONONONONONO, when she turned the tap on. Boom! The flame reached the ceiling.

We have all sorts of these things in the lab. I could spend a day just relating lab and AF stories here for APUG.

whicever is applicable.

PE

 

[Thomas Bertilsson]

How is the citric acid stop bath from Silvergrain? Is that a worthy substitute, and could one potentially use that in lieu of acetic acid?

 

[Photo Engineer]

I have made up some Citric Acid stops and the results vary as a function of formulation.

I would say that if it works, use it.

PE