Here's my little contribution to your question:
A silver image obtained from a silver chlorobromide emulsion put in an
alkaline selenide becomes reddish, what is attributed to a selenium coating
on the silver particles. It should be a silver selenide layer I think.
Better results are obtained with lightly developped images.
One obtains a good selenium toning using sodium hyposelenite Na2Se2O3
obtained by action of a big excess of sodium thiosulfate (or ammonium
thiosulfate) on sodium selenosulfate. The latter being produced by
dissolving selenium in a boiling solution of sodium sulfite. The toning
solution has to have about 1 g of selenium per litre. The process is
accelerated by ammonium chloride.
For example, here is the T55 recipe (where you do not have thiosulfate,
surprisingly, maybe a mistake in the book):
Water QS 1000 ml
Anhydrous Sodium Sulfite 150 g
Boiling Selenium 6 g
Ammonium Chloride 190 g
To tone, add 5 parts of water. Tone for 3 to 10 minutes. Wash 15 min
Selenium may be used combined with sodium sulfide under a selenosulfide
form: 5 g of selenium for 135 g of sulfide in 200 ml warm water. The
solution is stabilized by a few ml of sodium bisulfite (or
hydrogenosulfite, NaHSO3). To tone, dilute it 1 + 20. A ferricyanide
bleached image takes in this solution, colder tones than with sulfide alone.
Source: "Chimie et Physique Photographiques", by Pierre Glafkides
Note:
Selenium from * selenium powder 99.5+% ref 20,965-1 28$/50g
without taxes
But I think Dick found cheaper.
The reason why you have to use all these components, I think, is that
sodium hyposelenite Na2Se2O3 is not commercially available. I checked in
many catalogues, and I work in a chem lab, so, ...
*
Sigma-Aldrich
1001 W. St. Paul Ave
Milwaukee, Wisconsin 53233
phone: 414 273-3850
fax: 414 273-4979
I hope this answers to your question.
Philippe
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