| Silver is a
naturally occurring element. It is unique in its ability to react to light, forming latent
images that can be developed later to produce photographs and motion pictures. Like other
valuable minerals, silver is also widely used in jewelry and coins, as well as in
silver-plating, sterling ware and mirrors. Major uses of silver in the United States include:
|
|
 |
|
| Photography is so much a part of everyday
life that we have come to take it for granted. But it is only recent generations that have
been able to record the special moments in their lives in high-resolution color photos.
Far from being a frivolous pleasure, photography fosters intergenerational communication
-- helping us remember the past and pass on a little bit of ourselves to future
generations. Besides preserving precious personal histories, photos have enabled humanity to preserve its common heritage -- the great figures and events that shaped our civilization and made us who we are today. |
|
|
President Lyndon B. Johnson
signs Civil Rights Act as Dr. Martin Luther King Jr. and others look on. |
Law Enforcement, Public Safety |
|
| Photography has much more mundane but still essential uses -- for example, in the ordinary mug shot. Hundreds of thousands of crimes have been solved and countless future crimes prevented through the availability of photographs made by police departments and jailers. Likewise, crime scene photos help police reconstruct crimes and are used as evidence in criminal trials. Photography is also used to reconstruct accidents and natural disasters as an aid in preventing their recurrence. | |
 |
|
| Silver-based images have uses far beyond the
aesthetic. In medicine, x-rays and other imaging techniques are vital to our health and
well-being. Indeed, the practice of modern medicine would hardly be possible without
them. In most instances, silver is not the first choice but rather the only choice. In photography, for example, other substances have been tested but none has been found that can produce photographic images with the quality and detail as silver . Silver has no adverse health effect on humans. In January,
1991 (56 FR 3573), the U.S. Environmental Protection Agency (EPA) dropped the primary
drinking water maximum contaminant level (MCL). They took this action because the effect
of silver was judged to be cosmetic. The MCL was downgraded to a secondary MCL, and the
concentration limit was doubled, to 0.1 milligrams per liter. More than a year
later, the agency dropped the human health portion of the ambient water quality
criteria for silver (57 FR 60858; 12/22/92) for the same reason. The hydrated -- or "free" -- silver species has the potential to be toxic in aquatic organisms at very low concentrations. However, free silver is an artifact of laboratory studies. When introduced into natural waters, free ionic silver immediately combines with sulfides, chlorides, organic materials or particulates to form much less toxic, or non-toxic complexes. These tend to settle into the sediments, which act as a “sink” or repository for these materials. "Free" silver is not a component of photographic process waste. The thiosulfate, sulfide and chloride forms of silver that are present in photoprocessing discharges, as well as in sediments and sludge, are hundreds to thousands of times less toxic than the "free ionic" form of silver. These combined forms of silver are not readily converted to the ionic form. |
|
|
All content Copyright © 2003-2006. All rights reserved worldwide. |
|
Photo Credits: Girl & Horse, www.kodak.com Pres. Johnson, White House Photo X-ray, www.microsoft.com Earth, www.nasa.com |
|
