Both potassium cyanide and mercuric chloride are intense poisons. Emphasis courtesy the Merke Index. They are extremely dangerous to use and to dispose of. In addition, mercury compounds are cumulative in their toxicity. While you may be lucky for a time repeated exposure is very dangerous. The symptoms of mercury poisoning are not pleasant even in non-lethal doses. One careless spill involving either chemical would require a hazmat team to decontaminate your house. Unless you have training in their use find another topic in photography to interest you.
The big problem is that you can't rule out the occasional stupid accident. My dad was a chemist who worked in the 1940s and told me about a co worker who broke a flask filled with pure alcohol on his bench. This pissed him off, he went to the hallway and lit a cigarette, incinerating his lungs and dropping him on the spot. Again, this is a story my dad told me, I wasn't there, but accidents happen..be careful with all chemicals...EC
I was teaching a chemistry lab many years ago. My class shared the lab with an honors class. One of the honors students had gotten permission to make PETN (plastic explosive) and his nitration reaction got out of control. Nearly blew up the lab before we got it into an ice bath to slow it down. Who was stupider; the student or the instructor. His instructor had stepped out for a cigarette!
My high stupid school chemistry teacher was coerced into allowing some students to bring an A&W soda jug, which was probably over 1/2 gallon and would be capped with a normal soda cap (3/4" hole), almost filled with sugar and poured sulfuric acid into it on the bench at the front of the room. I was lucky to be in the back of the room when it blew. That was Mr. Engelmeyer's last day on the job. Sorry to take it off track, but simple things can have big results..EC
For those practicing WPC: safe disposal of KCN fixer
Rather than starting a new thread I append on this one, also since there is a lot of info on the hazards of working with KCN within.
For those people working with wet plate collodion and using KCN as fixer (please do not start debating on KCN, see above..)
I have written up and attached a simple and cheap procedure to destroy your exhausted KCN fixer.
Included is a recipe for an indicator solution to test for free KCN.
It is not my finding although I tested it and wrote it up. Obviously I can not be held responsible.
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Once I learned the profession of an electroplater. Cyanide is very common there. And we destroid it usually with hypochlorite. It works fast, is cheap and an surplus doesn't count too much.
Thanks for the information Cor. I'll try that If I get the chance.
Do you have the ability to post the procedure for using hypochlorite?
Originally Posted by piu58
The PDF file is that procedure!
Ahhh thanks PE,
I was in a rush and didn't the the chance to google hypochlorite and learn its bleach.
Egg and face were on collision course
Bleach fixers for collodion
Here are another couple of suggestions of possible alternatives to potassium cyanide fixer.
One of the supposed advantages of cyanide is said to be that it clears highlights whereas ammonium thiosulfate does not. I doubt this is strictly speaking true: extended fixing times are likely to decrease the density of all silver images (collodion is only a different binder, after all!).
Subsequent treatment of collodion negatives in Farmer’s reducer has already been suggested earlier in this thread, but ammonium thiosulfate bleach / fixers might also be worth exploring.
A very simple reducer that that could be used immediately after conventional fixing is Henn, Crabtree and Russell’s ammonium thiosulfate reducer, first published in PSA Journal (Photographic Science and Techniques Section) 17B, November, 1951. A more accessible summary appears in the chapter on reduction in Grant Haist’s Modern Photographic Processing, pages 71-74.
This ammonium thiosulfate reducer has the advantage of being very easily formulated by adding a solution of citric acid to a normal fixing bath. It might not be such a good idea to throw citric acid powder straight into your used fix: Kodak suggests dissolving the citric acid in the water used for the dilution to avoid sulfurization of the thiosulfate in the fixer. Kodak’s published instructions appear in J-1, Processing Chemicals & Formulas for Black-and-White Photography and F-40 Conservation of Photographs. Basically, Kodak Rapid Fixer [or the Ilford equivalent] is diluted as recommended for the rapid fixing of negatives, and then 15 or 30 grams per litre of citric acid is added. The smaller amount of citric acid is recommended for prints and fine-grain negatives, the larger amount for negatives; how well it works on collodion negatives is likely depend on the structure of the its image silver.
One possible downside is that this ammonium thiosulfate reducer does, however, smell of sulfur dioxide (not to be confused with hydrogen sulfide), so it should be used with good ventilation and not near sensitized photographic materials. The solution is colorless, so the reduction process can be observed easily; with a heavily overexposed conventional negative it seemed to be much less rapid and easier to control than Farmer’s reducer, taking about 2 to 5 minutes.
Another bleach/fix probably closer to those used in color processing might be derived from United States patent 4,191,575 of Mar. 4, 1980, by Donald J. Sykes and Louis D. Pratt of Philip A. Hunt Chemical Corporation of Palisades Park, NJ, titled (rather long windedly) "Two-step photographic processing of black and white images which enhances the images by controlled bleaching during fixing immediately following development and which produces black and white images with reduced density in low density areas".
To an essentially conventional ammonium thiosulfate fixer, Sykes and Pratt add between 10 and 40 g/litre of a 31.7% by weight solution of Sodium ferric ethylenediaminetriacetate. In addition, 5 g/litre of thiourea serves as an accelerator. Although citric acid is cheaper, Ferric Sodium EDTA is still relatively inexpensive at Photographer’s Formulary; Photo Engineer has previously commented that there are better alternatives for color blixes, but it may still be worth exploring for collodion, where only mild bleaching seems desirable.
If image color is dependent on the morphology of the original silver image, then logically it ought to be possible to achieve the same result (i.e. the same size silver particles, and the desired warm tones) by fixing in something other cyanide.
Thiourea, which was previously suggested above, is probably also worth a try. If William Henry Jackson washed his collodion negs in 160 °F / 70 °C hot water from a geyser, reticulation is unlikely to be the problem it might be for gelatin!