Bleach-fix regeneration kit and use thereof in photographic processing
US5055382A · kind A · utility
Inventors
Key dates
| Filing date | Feb 1, 1989 |
| Grant date | Oct 8, 1991 |
| Priority date | — |
| Expiry date | Feb 1, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG03C7/44
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A three-part bleach-fix regeneration kit is utilized to restore the capability of a spent bleach-fix solution to function as a working solution in photographic processing. The first part, which is an aqueous alkaline solution containing a buffering agent and an aminopolycarboxylic acid, is added to the spent bleach-fix solution prior to electrolytic recovery of silver therefrom. The second and third parts, which are aqueous acidic solutions containing, respectively, an iron salt and a thiosulfate fixing agent, are added after electrolytic recovery of silver. The first part functions to increase the pH of the spent bleach-fix solution to a level at which electrolytic silver recovery is optimized, while the second and third parts function to lower the pH to an optimum level for use in photographic processing. In addition to providing the necessary pH changes, addition of the three parts in this manner restores all necessary components to their proper concentration. Reaction of the aminopolycarboxylic acid and the iron salt brings about in situ generation of the complex which functions as the bleaching agent.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.