Photographic Chemicals
Photographic chemicals at Lincoln University are primarily used in the print shop. The print shop uses developer, stop bath, and fixer in its photographic production process. Exposed film is placed in the developer solution, which changes silver ions on the film into black metallic silver. This creates the film image. A stop bath is used to halt the developing process to prevent the picture from getting darker. Fixer then makes the image permanent and light-resistant by dissolving any remaining silver halide salts. 
Developer solutions and powders are often highly alkaline and are moderately to highly toxic. They are also sources of the most common health problems in photography; skin disorders and allergies. Developers are skin and eye irritants and many are strong allergic sensitizers. Some common ingredients in developers are hydroquinone and sodium sulfite.
Hydroquinone can cause de-pigmentation and eye injury after five or more years of repeated exposure, it is also a mutagen.
Sodium sulfite decomposes to produce sulfur dioxide (a toxic gas), when heated or allowed to stand for a long time in water or acid.
Stop Bath
Stop Bath solutions and powders are often highly acidic and are moderately to highly toxic. The most common chemicals typically used for stop baths are acetic acid or citric acid. The acids commonly found in stop baths can cause dermatitis and skin ulceration and can severely irritate the respiratory system. Contamination of the stop bath by developer components can increase inhalation hazards.
Potassium chrome alum, sometimes used as a stop hardener, contains chromium and can cause skin and nasal irritation, ulceration and allergies.
Disposal Information for Developer and Stop Bath
Any solution of developer or stop bath is considered a corrosive hazardous waste and cannot be disposed of down the drain unless it is treated to remove this characteristic. The developer and stop bath must be combined in a container to neutralize the solutions before being put down the sink. If this combined solution of developer and stop bath is not within the appropriate pH range
(5.5 <pH< 10.5) adjust with appropriate chemicals. Please follow drain disposal guideline flushing with at least 10 -20 times as much water as the solution when disposing. Typically developer and stop bath are completely used up and hazardous waste disposal of unused amounts of these chemicals is not typically required. 
Fixer contains sodium thiosulfate, sodium sulfite and sodium bisulfite. It may also contain potassium aluminum sulfate as a hardener and boric acid as a buffer. Fixer solutions slowly release sulfur dioxide gas as they age. However, when these solutions are contaminated with acid from the stop bath, the gas sulfur dioxide is released at a more rapid rate.
Sodium sulfite decomposes to produce sulfur dioxide, when heated or allowed to stand for a long time in water or acid.
Sodium thiosulfate upon heating or a long-standing solution can also decompose to form highly toxic sulfur dioxide gas. Many asthmatics are particularly sensitive to sulfur dioxide.
Sodium bisulfite also decomposes to form sulfur dioxide if it makes contact with boric acid or acetic acid.
Boric acid is moderately toxic unless there is an exposed wound on the skin, then it can be highly toxic.
Disposal Information for Fixer

No concentrated photographic chemicals of any kind can be placed in the trash or down the sink for disposal. Before any spent fixer solution can be disposed of via the drain it must be treated with some type of silver recovery unit. This unit treats the spent fixer so that it may be discharged down the drain. There are relatively inexpensive simple silver recovery units that can capture the silver in a bucket that can be recycled.   These units will adequately remove the enough silver to remove the D011 toxic hazardous waste characteristic listing from the solution. If a silver recovery unit is not used, the Hazardous Materials Compliance officer must handle the spent fixer as a hazardous waste.   If you need a waste pick-up or have any questions regarding material management please contact Robert Clay, Hazardous Materials Compliance Officer at 681-5497 or