Correct... not all sites show a difference. I think the FSA or thiourea dioxide toner is more for a special effect. Since you read about it in Tim's book, did you get the result you were after, even though it was slow in working? I suspect you didn't, in which case you might need to spring for it, if that is really a look you are after.... Ray --- On Wed, 2/23/11, Eric Nelson <emanmb@xxxxxxxxx> wrote: From: Eric Nelson <emanmb@xxxxxxxxx> Subject: [pure-silver] Re: Thiourea and Thiourea dioxide To: pure-silver@xxxxxxxxxxxxx Date: Wednesday, February 23, 2011, 3:57 PM I looked it up myself and found these for t. dioxide with the 2 different CAS #'s: http://www.lookchem.com/cas-418/4189-44-0.html http://www.thiourea-dioxide-fas.com/ <--CAS# 1758-73-2 This is what I found for my thiourea: http://www.jtbaker.com/msds/englishhtml/t3107.htm I won't pretend I know anything about what's on those pages as I'm just looking for the practical application of the compound with this toner. I used my thiourea anyway as I was in a testing mode yesterday and did get toning, albeit very slowly, of the prints I had bleached with the ferricyanide/pot. bromide combo. That may be my "practical" answer right there, but since I work w/chemicals w/o getting into molecular structures and formulas, I'm hoping someone who does might know the answer if it's 'worth' looking into getting the t. dioxide or not. Eric From: Ray Rogers <earthsoda@xxxxxxxxx> To: pure-silver@xxxxxxxxxxxxx Sent: Wed, February 23, 2011 4:45:55 AM Subject: [pure-silver] Re: Thiourea and Thiourea dioxide Sources I looked at gave different yet presumably equvilant structures for those two cas #s Thiourea is different. ??? Thiourea sulfoxide? Did you mean thiourea dioxide rather than sulfoxide? (Can you supply the CAS # for that?) Ray --- On Wed, 2/23/11, daniel <daniel.bouzard@xxxxxxxxxx> wrote: From: daniel <daniel.bouzard@xxxxxxxxxx> Subject: [pure-silver] Re: Thiourea and Thiourea dioxide To: pure-silver@xxxxxxxxxxxxx Date: Wednesday, February 23, 2011, 7:01 AM Hello, CAS 4189-44-0 and 1758-73-2 are both for thiourea dioxide under different names. CAS 62-56-6 is for thiourea. Several years ago I tried toning with thiourea sulfoxide following Tim book and it worked very well. Daniel Bouzard Le 22/02/11 23:25, Eric Nelson a écrit : I'm working from Tim Rudman's toning book and am playing with the FSA toner. In it he lists thiourea dioxide to be used in the toning bath. Now I have thiourea that comes from TechChem down in Missouri and called them to see what flavor of thiourea I have. Bob called back and he found something odd in the CAS listings. TechChem's thiourea is CAS# 62-56-6 Thiourea dioxide has TWO CAS #'s which he says is "unheard of". CAS# 4189-44-0 and CAS# 1758-73-2 Since Tim has been known to hang around these parts and others here may be more familiar with the CAS catalog system, I'm wondering if these 3 compounds are interchangeable or what? Thanks Eric