How These Canisters Work:
As used fixing solution or wash passes through the steel wool fibers, the silver ions in the solution are exposed to the iron ions in the steel wool. The silver ions combine with sulfar and forms a precipitate that falls into the collection chamber at the bottom of the canister as "sludge".
The 'up-flow' design of the Rotex Silver Compliance Canister allows most of the precipitate to fall freely and not clog up the steel wool. Some of the silver-bearing precipitate is likely to adhere to the steel wool fibers and both the used steel wool and sludge are smelted in a reverberatory furnace to recover the silver. A single pound of steel wool may recover as much as 6 to 9 Troy Ounces of silver in a normal operation.
Time of contact between the solution and the steel wool is very important for the exchange to take place. If the solution passes through too quickly some silver will not be trapped. A very high flow may even wash out the sludge. At the recommended flow rates, solution entering the steel wool at 50 ppm (parts per million), also defined as 50 mg per liter - will ususally give up approximately 95% of its silver and exit the canister well below 5 ppm.
Where environmental protection requires that the solution be stripped to 1 or 2 ppm, a second canister is connected in series to the first. Use a taller model for the secondary canister.
- Type C (Course Grade) - For use with graphic arts and X-ray fixers with Part B hardeners; color paper bleach-fix and E-6 color slide fix.
- Type M (Medium Grade) - For use with other black & white fixers without Part B hardeners; C-41 Fixers and stabilizers; fixers for microfilm and cine films; wash water.