Potassium Ferricyanide - How Toxic

[Mike]

I have recently started mixing my own Potassium Ferricyanide bleach for
use in developing C41 film. My Darkroom Cookbook says that Potassium
Ferricyanide is "poisonous" and gives first aid instructions but doesn't
tell how toxic it is.

Is this stuff "rubber gloves and dust mask or your going to die" type of
toxic or is it merely "if you drink a little your going to be sick for a
while" toxic?

Thanks in advance
Mike

[Francis A. Miniter]

Dear Mike:

One of my favorite novels, "Love in the Time of Cholera" by Gabriel Garcia
Marquez, begins with a doctor being called to the house of an old friend of
his, a photographer who, having decided not to grow old, has heated up some
potassium ferricyanide and committed suicide. Not wishing to determine if
this experiment is repeatable, I have treated the stuff with considerable
respect, using gloves when dealing with it in solid form. I have been
comfortable enough with my pouring techniques that I have not done the same
when using it in liquid form. But you will find that it will bleach just
about anything. I wash my hands very carefully after holding the bottle in
which it is stored, so as not to risk putting any of it in my mouth.

Francis A. Miniter

[GeoS]

In article <MPG.119ffd031...@news.cooke.net>, mi...@cooke.net
(Mike) wrote:

>I have recently started mixing my own Potassium Ferricyanide bleach for
>use in developing C41 film. My Darkroom Cookbook says that Potassium
>Ferricyanide is "poisonous" and gives first aid instructions but doesn't
>tell how toxic it is.
>
>Is this stuff "rubber gloves and dust mask or your going to die" type of
>toxic or is it merely "if you drink a little your going to be sick for a
>while" toxic?
>

I wouldn't drink it but it's not particularly toxic.

George Struk - Natural Light Black & White Photography
http://www.accesshub.net/naturalight

[DMorring]

>Ferricyanide is "poisonous"

Mike,
Do be careful!
cyanide + koolaide = Jonestown
cyanide + acid = gas chamber
Dave

[Frederick Perry Arnold Jr]

Obj Disclaimer:
I'm an inorganic chemist, and this comes straight from the
book and the MSDS, but is certainly not endorsed by U. of C. With that
out of the way....

Those examples are free hydrogen cyanide (HCN). Ferricyanide is
Fe(CN6)+2, rather stable (look how long blueprints/cyanotypes last), but
certainly toxic if you eat too much of it. The CN groups are tightly
bound to the iron (which is the mechanism of toxicity of cyanide gas; it
can't be displaced by dioxygen once bound) and won't come off except it
the presence of very strong acids.

Be careful with it around strong acids, Do Not mix it with oxidizers (like
perchlorates or silver sand), don't inhale the powder, and wearing gloves
wouldn't be bad either, but I've handled it in the lab (chemistry) for
years, and it falls under the "don't put your tongue on it" category, not
the "look at it cross-eyed and die" category. If I read the spec sheets
correctly, it's more of a danger as an explosive if mixed with the right
oxidizer than as a poison.

For the more technically minded:

LD50 2.97g/kg (i.e. if you weigh 142 lbs, like myself, you have to eat 191
grams, or roughly 2/5 of a pound, of it in order to have a 50% chance of
fatality.). In reality, it's the quantity at which 1/2 of the test
population dies, but good enough for our purposes. The MSDS really
overstate the hazards, only because they're designed for industrial scale
quantities, and not lab/photo scale. (MSDS for sand {yes, beach sand}
lists all sorts of hazards and advises protective clothing, because on the
ton scale you can get enough dust to cause silicosis. I had to label the 2
lb sand buckets at work once because of this listing, even though we'd
never had an incident of someone snorting sand until they got ill)

>>Ferricyanide is "poisonous" >
>Mike, >Do be careful! >cyanide + koolaide = Jonestown
>cyanide + acid = gas chamber >Dave

and ferricyanide + koolaid = sticky film bleach, that even Walgreen's
photofinishers wouldn't use (probably).

--
"No science has ever made Frederick P. Arnold, Jr.
more rapid progress in a A&HPRC, U. of Chicago
shorter time than Chemistry." 5640 S. Ellis Ave
-Martin Heinrich Kloproth, 1791 Chicago, IL 60637

[Jeanette D. Walton]

Further to your point, Kodak recommends not mixing household chemicals (i.e.
Clorox) with minilab chemistry for exactly the reason you describe.

It makes my hair stand on end when I think of the stuff in Chemistry Sets from
the 1950's, however - -