And I think that it was Ryuji Suzuki who wrote here that silver in used fixer put into the sewer would rapidly combine to form silver sulphide which is chemically very inert (which is why it's good for archival treatment of prints). In the sewer there is no shortage of sulphur-containing compounds to facilitate this reaction!
John ================= Richard Knoppow wrote:
----- Original Message ----- From: "Ralph W. Lambrecht" <info@xxxxxxxxxxxxxxxx>To: <pure-silver@xxxxxxxxxxxxx> Sent: Monday, February 01, 2010 9:34 AM Subject: [pure-silver] Re: Measuring low levels of silver in fixerI think there are two issues here which should not be confused: First is determining when there is too much dissolved silver in the fixer for it to fix correctly, the second is determining when it has too much silver to pour it down the drain. While large labs have the means to analyse the silver content of fixing baths I think this is overkill for most amateur, and even most pro photographers. The best test is to fix out a sample of film or paper and test it for residual silver using either the sodium sulfide or rapid selenium toner test solutions. For discarding fixers one can remove quite a bit of the dissolved silver using such simple means as steel wool to collect some of it. After treating this way most of the silver will have plated out on the wool, which can then be processed by a silver reclaimer and the residual liquid disposed of down the drain. BTW, for small amounts of fixer much of the dissolved silver will simply plate out on the drain pipes. One of the main problems with silver in drain water is that it can kill off micro-organisms which are part of the food chain. Many environmental issues seem not to make too much sense because they are not followed along far enough to understand the damage that can be done.PeterI forgot to add that the reason I wouldn't necessarily do as Ralph suggested and use test strip to determine 1g/L then dilute to 50ppm is that I often leave my fixer out in a tray in my sink and the clearing time reaches unacceptably high values before the silver concentration will even reach 1g/LWhy would that be? Regards Ralph W. Lambrecht http://www.darkroomagic.com-- Richard Knoppow Los Angeles, CA, USA dickburk@xxxxxxxxxxxxx============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.
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