Photography by Kulvir and Cintie
Photography + Chemistry = ?
The Effects of Silver on the Environment
Photography is the practice of creating durable images by recording light or other electromagnetic radiation, either chemically (by the means of a light-sensitive material such as photographic film) or electronically (through an image sensor).
- With photographic materials, the silver nitrate becomes salts called silver halides.
- The silver halides have low water solubility and they’re left on unprocessed film or paper.
- When the film is being processed, most of the silver is removed, but it can sometimes be left.
- It is water soluble, but because of its strong hold, it does not dissociate (unlike most silver compounds).
- 90% of the time, the silver will be recovered and given to a refiner to be converted and purified into metal.
- The remaining 10% would still be bound together chemically along with waste water (from the processing activities) and discharged.
Redox Reaction:
Oxidizing and Reducing Agents:
Reducing Agent: Br (Bromine)
Substance being oxidized: Br
Oxidizing Agent: Ag (Silver)
Substance being reduced: Ag
There are three different redox reactions in black-and-white photography:
1. The film negative is an emulsion of silver bromide:
Ag+(aq) + Br—(aq) AgBr(s)
2. The film is processed, and the remaining Ag+
(aq) is converted to free silver by a reducing agent.
An appropriate solution process removes the unreacted AgBr. This step produces the negative.
3. The negative is then printed onto photographic paper.
- The discharges are treated at waste water treatment plants.
- The silver that is released from the treatment plants is gone into bodies of water.
- Since it’s still chemically combined, it can naturally react with other chemicals in the water and prove to be toxic.
Conclusion
Silver halides are used in film and photographic paper. It's the process of removing silver to create the image that was taken, that would be referred to as redox. We learned that photography is not just a simple, easy process. It is, in fact, a very complex and intricate process that includes Bromine and Silver! So the next time you take a photo, remember what actually happens when you capture your precious moments.
Sources
A.W Traden and T.W Bober. (2002). Environment Information from Kodak. Retrieved January 15, 2014, from Kodak: http://www.kodak.ca/ek/uploadedFiles/J-216_ENG.pdf
Levin, J. (n.d.). Light and Color. Retrieved January 15, 2014, from Physics 1230: http://www.colorado.edu/physics/phys1230/phys1230_fa01/topic51.html
God :)
Omar Alvarado, Thomas J. Fellers and Michael W. Davidson. (2003, August 1). Polarized Light Digital Image Gallery. Retrieved January 15, 2014, from Molecular Expressions: http://micro.magnet.fsu.edu/optics/olympusmicd/galleries/polarized/silverbromide.html
Photography. (n.d.). Retrieved January 15, 2014, from Merriam-Webster: http://www.merriam-webster.com/dictionary/photography
Silver-Ag. (n.d.). Retrieved January 15, 2014, from Lenntech: http://www.lenntech.com/periodic/elements/ag.htm
Reaction Application
Photography (both black and white and colored) has always depended on silver, even earlier in history. The reasons being that silver iodide and silver bromide are sensitive to light. So when they are coated on film and are exposed to light, the silver ions go towards the metal in tiny nuclei. This causes more silver to be in the nuclei, as the film gets developed with a reducing agent.
Energy Consumption
Possible Test Questions
Photography is the process of producing pictures by radiant energy (energy of electromagnetic waves) and photosensitive surfaces. Photosensitive surfaces react to silver, and this makes it sensitive, and that's how photographs are produced.
1) What are the two ways that photography is practiced?
2) What is the common redox reaction involved with photography?
3) When silver nitrate becomes a salt, what is it called?
4) How can the silver compounds that remain in water make it toxic?
5) Why is silver highly dependent on in photography?