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Photographs of the Past: Process and Perservation
In recent years, interest in old photographs has grown significantly among a broad public, from collectors, conservators, and archivists, to amateurs seeking to preserve precious family albums. Although the medium of photography is barely 150 years old, its relatively brief history has witnessed the birth of a wide range of photographic processes, each of which poses unique conservation challenges.
Photographs of the Past: Processes and Preservation provides a comprehensive introduction to the practice of photograph preservation, bringing together more information on photographic processes than any other single source. Introductory chapters cover issues of terminology; the rest of the book is divided into three parts: positives, negatives, and conservation. Each chapter focuses on a single process--daguerreotypes, albumen negatives, black-and-white prints, and so on--providing an overview of its history and materials and tracing the evolution of its technology. This book will serve as an irreplaceable reference work for conservators, curators, collectors, dealers, conservation students, and photographers, as well as those in the general public seeking information on preserving this ubiquitous form of cultural heritage..
Price: $31.57 [Notify me when price goes down.]


Phototransformation of methabenthiazuron in the presence of nitrate and nitrite ions [An article from: Chemosphere]
This digital document is a journal article from Chemosphere, published by Elsevier in . The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
The influence of nitrate and nitrite ions on the degradation of methabenzthiazuron upon irradiation using artificial solar light has been investigated. The rate of degradation of methabenzthiazuron (1@mM) was accelerated by NO"3^- (0.1mM) by a factor of 10. The irradiation of methabenzthiazuron (0.1mM) in the presence of NO"3^- (1mM) or NO"2^- (0.1mM) yielded numerous intermediary photoproducts. Mineralization was achieved after prolonged exposure. Some were identified with the help of LC-ESI-MS and flow injection APCI-MS techniques. Both oxidations of the aromatic ring and of the urea chain were observed. The former started by hydroxylation of the ring. Further oxidation of the ring led to cleavage of the benzenic ring with formation of dialdehydic, diacidic and anhydric compounds. Complete removal of the lateral urea chain took place subsequently to demethylation of the terminal methyl group and loss of the CO-NH"2 group. Nitration was a minor process. This work shows that the photodegradation of methabenzthiazuron in the presence of nitrate or nitrite ions is highly non-specific. .
Price: $8.95 [Notify me when price goes down.]


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