The whole idea of mixing he HCA with selenium was to eliminate the HCA after toning. You're doing it one-step. I personally do not like that way. I dilute selenium with water 1+3 and do the HCA after a water rinse. By diluting the toner with water you can extend the life of the toner. Toner is much more expensive than HCA.
It is generally not recommended to dilute selenium toner with hypo clear. The toner lasts a very long time, the HCA not. so you'll be wasting good toner...
A few days ago I decided to intensify an irritatingly flat negative. I bleached in pot.ferri/bromide, then redeveloped in a pyro/carbonate mix. Worked like a dream, gave lots better highlight separatoin, and is reversible in case I don't like the result.
this brings up a point: How does one know when the HCA has gone bad? As of right know, I used the fixer as the meter. Fixer just went bad, so my HCA should be bad as well, right?
By the way, the HCA I used in and following the selenium were fresh...
Good question - and one I've never thought about!
Sulfite can oxidise to sulfate, absorb sulfide and turn to thiosulfate, or (eventually) decompose to sulfur and sulfate - just like thiosulfate does.
I've never been in the habit of using HCA, so the question has never occurred to me. Anyone with any good leads?