Sodium Thiosulphate solution

[tcyiu]

A LFS is going out of business, and amongst the stuff I bought was a bottle of sodium thiosulphate solution for $4. Dosage is 1 teaspoon per 75 gallons, so it is much more concentrated than the normal water conditioners one buys.

BUT the solution is yellow. I did some reading and found that sodium thiosulphate reacts with acids to form sulphur which is the yellow color.

Na2S2O3 + 2HCl → 2NaCl + S + SO2 + H2O

My question is, is this reaction reversible? meaning can I still use this bottle? With my rudimentary knowledge of chemistry I would say that it is probably not easily reversed since this is NOT the path for forumlating Na2S2O3.

For those of you who mix your own conditioners from Na2S2O3 crystals, do you see yellowing in your solutions?

Thanks,

Tim

[Harriett]

When I use it, I just take crystal grains and toss them to melt in the tank just as I begin to fill. I got a tub of maybe 1.5 cups worth, from PondDepot.com---it was like $6 a few years ago. It takes about 2 grains / 40g. Lasts forever. For chlorine, but not effective if you have chloramines.
I have never seen any yellow color come off of it. I would err on the side of safety and not expose my fish to it. Doesn't sound right to me.
Best regards,
Harriett

[Rod]

For those of you who mix your own conditioners from Na2S2O3 crystals, do you see yellowing in your solutions?



No, never seen yellowing. I'd throw it. It is very cheap to buy, not worth the risk imo. Try a swimming pool shop, they are much cheaper than the aquarium industry for this sort of stuff.

Rod:)

[fishorama]

My husband (a chemist) said it will have a very noticable stink if it has gone bad. I think my last bottle of genesis was yellowish but he said it's ok

[tcyiu]

My husband (a chemist) said it will have a very noticable stink if it has gone bad. I think my last bottle of genesis was yellowish but he said it's ok

Yup. Rotten egg smell. Gone bad. Durn it. Live and learn.

Tim

[tcyiu]

Here's a quick update. The rotten egg smell was present when I first opened the bottle. After a day or so (i.e. after I got your replies), I went back and smelled it again. No more smell.

So I ran a small test. I used 1/4 teaspoon of this and my regular stuff to de-chlor the tap water which in the recent weeks have reeked of chlorine. (I think they do this around Indian Summer which gets pretty warm.).

The fish did not react negatively. So the next day, I increased the amount and decreased the my regular stuff. Again 75% water change. Again, not adverse reactions.

So now I am using this stuff only. In fact, at twice the recommended dosage because of the increased chlorine presence. Everyone is fine. Adults, juveniles, cardinals, clown loaches. No one seems affected.

So the update is, a yellowing of the liquid does not necesary mean the solution is no longer effective.

Tim