I was re-reading this and related threads today at lunchtime and I am having trouble wrapping my head around how to make up the solution necessary to use for sensitizing. No doubt I'm making this much harder than it is by going through this in my head while I am supposed to be doing real work. Gotta get this off my mind.

Let's assume for example, my usual batch contains 6g of AgNO3 ending up with about 150ml of emulsion. I want to use sulfur + gold at a rate of 3:1. Furthermore, I have data that tells me that the sulfur is sodium thiosulfate (Na2S2O3·5H2O) used at 3.8x10^-6 mole per mole Ag. I will also use Chloroauric Acid (HAuCl4) as a 1% (w/v) solution for the gold.

- So, at 169.87 g/mol for AgNO3, that is 0.035 mol of Ag.

- at 248.18 g/mol for Na2S2O3·5H2O, 3.8x10^-6 mol is 0.00094 or about 1mg.

- and I would want 1.3x10^-6 mol HAuCl4 per mol Ag

- so at 393.83 g/mol for HAuCl4 (assuming trihydrate) that would be 0.00049 or 0.5mg

(Have I got it right this far?)

OK. If I make up a 1% solution of thiosulfate (1g/100ml H2O) each ml contains 10mg (0.01g thiosulfate. Likewise for the gold chloride solution. If I add the Na2S2O3 and HAuCl4 to a solvent (H20?) in a ratio of 3 to 1 I have my 3:1 ratio. So let's say in 100ml total, I have added 3ml thisulfate solution and 1ml HAuCl4 solution.

If I had a mole of silver at this point it would be simple enough, I suppose. But I have 0.035 mol of Ag. This is where I get stuck! I can use Denise's Steigman's formula because she says how to make and use it.

What sort of a solution do you make? I'm lost.

Thank you all for any help.....

-- jason