The lines in the figure indicate bonds. Two lines = double bond which means it requires more energy to release. That OH group probably comes off easily or easier than the other groups. With seeing the whole process, ions running around, etc I won’t even go any further. Not that I am totally qualified to do so either. pH can be a big issue in making toning happen as it put in motion the bonding that will or can take place. The different CAS # may be ( just a guess) due to a registration by the one company with its name. If the formula calls for FAS – the later two, it may be a pH issue. (NH2)2.CS from JT baker The other two sources. CH4N2O2S · CH4 N2 O2 S <http://www.lookchem.com/300w/2010/0621/4189-44-0.jpg> Molecular Structure of 4189-44-0 (Methanesulfinic acid,1-amino-1-imino-) Good luck. Eric Neilsen 4101 Commerce Street, Suite 9 Dallas, TX 75226 214-827-8301 <http://ericneilsenphotography.com/forum1> Let's Talk Photography www.ericneilsenphotography.com SKYPE ejprinter From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Gerald Koch Sent: Thursday, February 24, 2011 8:37 AM To: pure-silver@xxxxxxxxxxxxx Subject: [pure-silver] Re: Thiourea and Thiourea dioxide Sodium bisulfate (sodium hydrogen sulfate) can be substitued for sulfuric acid in many photo formulas. It has the afvantage of being a solid and hence safer to use than the acid. It can be obtained from many sources. It ir sold as pH-Minus for adjusting the pH of swimming pools. Jerry _____ From: Eric Nelson <emanmb@xxxxxxxxx> To: pure-silver@xxxxxxxxxxxxx Sent: Thu, February 24, 2011 9:14:41 AM Subject: [pure-silver] Re: Thiourea and Thiourea dioxide I used the iodide version as I had the chemicals for that; I don't have sulphuric for the other bleach. Using the iodide bleach once you see the image starting to lighten, it's pretty much time to pull the print as the toner doesn't add density in my case and perhaps it was because I was using RC paper. Also the tip in Tim's book of re-bleaching (if I don't like the results of the toner) and then putting back into a developer (assuming dektol etc was meant) didn't work here either. Of course looking at the chemical formula for TD vs my thiourea I see that they look very different so thhat may explain a lot, but what that means chemically I have no idea. Eric _____ From: "C.Breukel@xxxxxxx" <C.Breukel@xxxxxxx> To: pure-silver@xxxxxxxxxxxxx Sent: Thu, February 24, 2011 7:30:34 AM Subject: [pure-silver] Re: Thiourea and Thiourea dioxide Hi Eric, I am surprised here: FSA is my favorite toner. I use it mostly on partially toned prints, because the density gain is considerable (your image can get 1-1 ½ stops darker on a completely bleached print, depending on the paper). I like the flexibility of the different bleaches. Redevelopment (FSA is not really a toner, see Tim’s book) in FSA is generally very fast: 30 sec-1 min., exception is after the Iodine bleach, than re-development takes a lot of time (by heart: 30 minutes or so) Good luck, Cor Btw my FSA http://tinyurl.com/669jflo Good luck, Cor _____ From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Eric Nelson Sent: woensdag 23 februari 2011 21:45 To: pure-silver@xxxxxxxxxxxxx Subject: [pure-silver] Re: Thiourea and Thiourea dioxide It worked ok-ish in that I did get toning eventually; it's very slow, and if you bleach too far tone doesn't come back as it does when sepia toning. It is a totally different process, and I understand that. The color I got was nice yellow-greenish brown. What I'd really like to find is a toner (besides tea and coffee) that adds a cream color to the paper. Presently just working with RC postcard paper so extended toning and washes aren't a best choice although w/RC I assume longer washes aren't necessary anyway. I'd just hate to send out a promo and have it turn brown.. i.e. brown in a bad way! Eric _____ From: Ray Rogers <earthsoda@xxxxxxxxx> To: pure-silver@xxxxxxxxxxxxx Sent: Wed, February 23, 2011 11:50:52 AM Subject: [pure-silver] Re: Thiourea and Thiourea dioxide 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