What are the chemical reactions upon which the photography industry relies
Just need a little help, l am working on a project for chemistry.
Hmmmm...been a while, but I do remember a few things. First in
the process would be the development of the latent image (on exposed film)
into the solid silver image. Photo film emulsions are typically made from
silver halides, the halides being typically bromide, chloride, etc.
When the silver halides (film emulsion) are struck by photons of light,
the electrons in the valence band of the halides jump to the conduction (?) band, creating a latent (invisible) image awaiting development. The developer reacts with the exposed silver halides, converting them into solid silver. It actually reacts with all silver halides, but works much, much faster on the exposed molecules. The second step of film development is the stop bath: acetic acid. It halts development of the film by lowering the pH of the (alkaline) developer below it is working limit. The third step (b/w film & paper only) is the fixer, which dissolves the unexposed silver halides, leaving only the solid silver on a clear acetate base: b/w negative film. Lastly, the dissolved silver needs to be removed from the fixer for both environmental (silver is a heavy metal) & financial (silver is $$$) reasons. There are two primary methods: electrolytic & metallic replacement. Metallic replacement using a steel wool cartridge. Dissolved silver from the fixer reacts with the iron on the steel wool The more active iron ions are displaced, & the silver ions are retained on the wool creating what is called ''silver sludge which can be shipped to a refiner for extraction of the solid silver. Electrolytic recovery involves a low current between a cathode & anode. During this process the cathode is coated with near pure silver. I used to be able to diagram the chemical reactions for each step, but that was 20 years ago & my brain has long since filed such information into a deep, dark place from which it cannot be retrieved. Hopefully, something here will be helpful. medifast codes medifast coupon number
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