RE: I have a question
Ryuji, Your figures re. pot. ferri. dilution are alarming, but at what point should the concentration be 1 p.p.m. - when it enters the drainage system, when it finally reached the treatment facility, or somewhere in between? Won't it also be diluted by waste water from other sources? Thanks, Liam -----Original Message----- From: BOB KISS [mailto:bobkiss@caribsurf.com] Sent: 21 October 2007 03:43 To: alt-photo-process-l@usask.ca Subject: RE: I have a question DEAR RYUJI, Please help here. I try to follow the rule of my last name, KISS, which stands for "Keep it simple stupid". I can't deal with hundreds of examples. You are the chemistry man so please suggest just one or two excellent silver bleach alternatives to potassium ferricyanide that would work and be more environmentally friendly (as well as regulation free), given standard silver gelatin processing procedures...yes, thiosulfate fix, washing, etc. It would be nice if they were readily available chemicals. To keep it simple, let's assume that we would want to bleach prints before toning. What do your recommend... CHEERS! BOB -----Original Message----- From: Ryuji Suzuki [mailto:rs@silvergrain.org] Sent: Saturday, October 20, 2007 6:49 PM To: alt-photo-process-l@usask.ca Subject: Re: I have a question From: Richard Knoppow <dickburk@ix.netcom.com> Subject: Re: I have a question Date: Sat, 20 Oct 2007 14:29:07 -0700 > Please give an example. You can get hundreds of examples by looking up US Patent 5391466. Iron (III) complex of some of the the compounds derived from Formula (II) in this patent, used alone, in a weakly acidic buffer, are an excellent b&w bleach with superior biodegradability. As usual of Konica patents it includes a ridiculously long list of many compounds taht can be potentially used, but one just has to think about which ones are easy, fast and cheap to make and the list immediately becomes much shorter. Fujifilm and AGFA also came up with different compounds that may be used similarly. Perhaps the compound (I) disclosed in US Patent 5149618 (assigned to AGFA) is related to the former patent's Formula II, although this compound is, of course, excluded from it. The best compound in the Konica patent is more biodegradable than the AGFA one. Bleaching agents that are one generation older, such as iron (III) EDTA or iron(III) DTPA bleach is poorly biodegradable but these are still much more preferrable to ferricyanide in terms of environmental damage. These compounds are also usable in mixture with thiosulfate as a stable print reducer, but generally speaking, you can get stronger bleaching action when bleach is used alone (oxidation potential is 100-200mV higher without fixer mixed in). -- Ryuji Suzuki http://silvergrain.org __________ NOD32 2604 (20071019) Information __________ This message was checked by NOD32 antivirus system. http://www.eset.com
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