Where the
world gathers for metal finishing
Q&As since 1989


-----

More Accurate Test strip for measuring Silver Content of FIXER

 

I am a service technician for pre-press graphic equipment. I am currently building two silver extraction systems for two customers who wish to meet or exceed the city of Toronto by-law specs on chemical waste(fixer). Building it is no problem but testing the results is the problem. I have contacted many companies(incl) Kodak, and the only test strips I have are measured in g/l of silver. The city of Toronto requires me to measure mg/l. For the passive part of the system, I will use a tank with steel wool [on eBay or Amazon]. The active part will include passing the solution through a cathode and anode, while the processor is in use. I have limited the voltage to approx. 1 volt and the current ranges between 200 ma to 800 ma, which I don't believe is enough to cause sulphiding. I have only done limited testing. The cathode is getting plated but I don't know how efficiently. I can experiment with adjustments, BUT if I can't measure the silver content accurately, I am 'handicapped'.

I would appreciate any guidance in this manner. I told my repair customers that I would build these at cost as long as they stop dumping this stuff into our environment. The monetary value of the silver is not an issue, we don't care. If you cannot advise me on the CURRENT requirement could you please tell me where to get more accurate TEST STRIPS.

Thank You,

Cal W [last name deleted for privacy by Editor]
- Newmarket, On., Canada

---

You don't want a test strip; you want a colorimeter. Several firms make them set up with kits for specific elements in the ppm range.

James Totter, CEF
- Tallahassee, Florida
 

I appreciate the response from James Totter. I did check with several scientific companies, and the closest, so far was mfg by HANNA. The problem was that the instrument, I don't know the name of it, measured too low, max range 1 mg/l because it was used for swimming pools. I am still searching and it might be easier now that I have an instrument name. Also I am getting a coating on the Cathode which does contain silver, but I suspect I am sulphiding because it wipes off with my finger BUT there was no hydrogen sulfide odor so I am getting contradictory conclusions.If the plating has a lower silver content, this is not important. The important point is...IS this reducing the usable FIXER which is circulating in the machine?

Cal W [last name deleted for privacy by Editor]
- Newmarket, On, Canada
 

---

June 6, 2008

Hi, Cal. Please see if you can locate a copy of Kodak's booklet "Recovering Silver from Photographic Materials"; it should answer most of your questions. You might expand your colorimeter vendor search to include Hach. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey