Shelf Life Of Sodium Thiosulfate In Anti-Chlorine

[Edwin_Thom]

Hi Randy,

I did a search in the web for the shelf life of aqueous sodium thiosulfate and found the shelf life of around 6 months in a few sites.

What puzzles me is, majority of the anti-chlorine products that contain sodium thiosulfate as dechlorinator have shelf life of >2yrs as indicated on the bottle. Is there some kind of "preservative" added to these anti-chlorine products to extend the shelf life of aqueous sodium thiosulfate beyond 6 months ?

[Randy Holmes-Farley]

I don't know the details of the stability of sodium thiosulfate, but I'd guess that part of the trick in setting shelf lives has to do with how much degradation one is willing to accept. In some applications, a 10% loss may be unacceptable. In other uses, having 50% of the potency remaining may be perfectly fine. The lower your criteria for acceptability, the longer the shelf life for the same bottle of stuff.

[Edwin_Thom]

Thks, Randy.

[Randy Holmes-Farley]

You're welcome.

Happy reefing.

[aquaman67]

I use sodium thiosulfate at work and 2 year old sodium thiosulfate still removes Chlorine accoring to a DPD test, if that helps.

[Edwin_Thom]

Originally posted by aquaman67
I use sodium thiosulfate at work and 2 year old sodium thiosulfate still removes Chlorine accoring to a DPD test, if that helps.

Thks for the info. Appreciate it. ;)

[Boomer]

The self lifes that you see for Sodium Thiosulfate, for 6 moths to 1 year are for reagent grade chemicals, such as those used for test kits. In solutions it is also a function of %, normaly 6 months for a 2 % soultion. The dry product has a longer self life of 1 year. It is a different issue for removing chlorine, which follows Randy's remarks.

[Edwin_Thom]

Originally posted by Boomer
The self lifes that you see for Sodium Thiosulfate, for 6 moths to 1 year are for reagent grade chemicals, such as those used for test kits. In solutions it is also a function of %, normaly 6 months for a 2 % soultion. The dry product has a longer self life of 1 year. It is a different issue for removing chlorine, which follows Randy's remarks.

Thks for the clarification, Boomer. ;)