Here is a formula which works quite well:-
Anhydrous Sodium Sulphite 150 grams
Distilled Water 750 ml
Dissolve Sodium Sulphite and bring solution to boil, and add very
carefully with stirring:-
Powdered Selenium 6 grams
Keep solution boiling and stir until Selenium has dissolved.
Cool to room temperature and add slowly with stirring :-
Ammoniun Chloride 190 grams
When dissolved make solution upto 1 litre with distilled water.
For toning, dilute one part of the above selenium concentrate with five
As you are doubless well aware, Powdered Selinium should be treated
with respect as it is fairly toxic. Avoid inhaling or ingesting the
powder and keep it off your skin, also when dissolving the Selenium in
the boilng sulphite solution, use a large vessel to avoid splashing, and
ensure that the working area is well ventilated.
Hope that the above is of use to you.
-- Alex Nanson email@example.com Gloucester. UK