Australia's Science Forum

Hi everyone,

I just started a new job as lab tech and I've been having issues with chemical waste. The kids are dissolving copper sulphate in warm water and adding iron filings into the solution. We get a brown precipitate which I filtered and dried, but I'm not sure if I can dispose it in the rubbish bin or not. Also the colour of the filtered solution is pale greenish-blueish, is it ok to pour down the sink?

Thanks in advance!

The green liquid is iron sulfate, probably with some copper sulfate left over. I'm assuming it's fairly dilute, and as long as you don't have litres and litres of it, it should be fine to dilute down the sink. The brown precipitate will be copper that has coated the iron fillings. Both of which are fine for garbage disposal

Copper sulfate shouldn't go down the sink, according to RiskAssess. I collect copper compounds in ice cream containers and leave them to evaporate. I scrape the crystals and left-over sludge into the bin (although if you want to be pedantic, that should really be saved for collection). I collect chromates and dichromates for collection, also all organics (halogenated and non-halogenated) and heavy metals such as lead, silver and zinc. Lead solutions I add solid sodium carbonate and allow them to react. The clear liquid can go down the sink and keep the lead residue for collection. Ditto using sodium chloride solution to precipitate silver out of solution.
Please post any questions you have here - knowledge is power! RiskAssess is an amazing resource if you have access to it.