Studies on the reducing properties of gelatin—kinetics of the reaction with copper (II) bis(bipyridine)

Abstract

Previously gelatins have been shown to reduce copper(II) bis(bipyridine) [CBB(II)] and that only sugars of the reducing substances, which are known to be gelatin impurities, reduced CBB(II). Even using high-performance liquid chromatography with electrochemical detection, in which the column eluent reacted with CBB(II), the reducing substances could not be identified with sugars. In the present paper the reaction rate of gelatins with CBB(II) was measured and compared with that of sugars. The rate constants of gelatins are very close to those of sugars with a hemiacetal structure, but addition of glucose to the second ripening solution for gold sensitization did not result in a significant effect on the photographic characteristics, while addition of glucosamine increased fog. It was concluded that the reducing properties of gelatin are attributed to amino sugars with a hemiacetal structure.

Keywords:

• reducing properties
• gelatin kinetics
• copper(II) bis(bipyridine)