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Just to be clear: my comment in the dichromate was motivated by Swedish environmental laws. Discharging Chromium ions in any oxidation state is illegal. Any large town will have a place you can send your collected waste, usually for free, but I don't know where that is in Göteborg. You just need to find the right 'gubbe' to ask.

FWIW, I am a physicist, was a Docent at Lund University and for many years was the Safety Officer for my Department.

I will leave the waste CLEARLY LABELED, at my local miljöstation, where I leave spent fixer etc. To be honest, I will not contact the environmental authorities in this matter as I'm already doing this illegally. I don't have a degree in chemistry, I don't have a lab that follows the very strict regulations of swedish environmental law. Getting a permit for this would most probably be impossible. If I knew someone at Chalmers college I would contact them, but I don't. Or maybe I do... will check out.