I generally am following Alan Greene's recommendation to keep separate bottles of silver nitrate exhausts and fixer ( sodium and ammonium thiosulfate ) exhausts for later disposal. He says if these are combined it could create sulfur dioxide gas, although a couple times I've mixed small quantities by mistake and never smelled anything.
I'm expecting some gold chloride in the mail tomorrow and am excited about trying some gold toner with my salt printing. My plan is to mix with borax or thiocyanate in small quantities to use 1-shot. My question: after using the toner, would it be better to add the leftover used-up toner to the fixer exhaust or the silver nitrate exhaust? My guess is that much of the gold will be gone and there will be silver dissolved in the thiocyanates, so it makes sense to put it in with the fixer, is that right? I'd rather not have to track a third stream of wastes if it's not necessary.
( Greene's book is usually pretty explicit about handling the different wastes, and he does mention toning with gold right at the end of his section on printing, but does not address this question. )