Australia's Science Forum

Can anybody advise on the disposal of 0.25M Sodium Thiosulfate that has been mixed with 2M HCl for the Yr 11 rates of reaction prac.

For the Sodium Thiosulfate

CSIS says down the sink
BUT
CHEMWATCH says- DO NOT discharge into sewer or waterways

then there is the added acid

I have litres of this and another class about to start

Please help me

We did this recently and it all went down the sink. Did it really say not to in CSIS? Can you tell me where you found that?

Woops hit the submit twice!!

I can not see the reason why it can not be disposed down the drain/ garbage. Salt, SO2(gas) and solid sulfur are products, you can filter solid sulfur and dispose of in garbage

CSIS says DO put down the sink but chemwatch says in red DO NOT

I imagine 10+yrs ago when CSIS was written that was the recommendation but I'm inclined to follow chemwatch recommendations as its the most up to date however it doesnt say how to dispose only how not to....

Sorry Jazz I didn't see your response when I replied to rae

that seems reasonable, thank you

Sorry I got it the wrong way around. We still put the lot down the sink. I'll need to have a chat to the teacher. I was unaware.

You could always store the solutions until you need some to treate waste dichromate and permanganate solutions from EEI and such.

These solutions are treated with just enough acidified sodium thiosulfate to exactly reduce the metal oxoanions (turning the solution pale blue or clear). Well, sulfuric acidification is preferred but a little chlorine won't adversely affect the process. The the metal ions are precipitated out as carbonates by slowly adding sodium carbonate; by the spatula sprinkle to avoid frothing. After standing overnight, the top solution (sodium -tetrathionate and -sulfate) is then decanted off, diluted fiftyfold, and washed to waste. The remaining metal carbonates slurry is then dried and contained for disposal.

I could read the answers but not reply as I was logged out accidentally and couldn't find my password. thank you for your responses.