Help Does SN degrade in water if left?

[Mongoose]

I made up a solution of 50 ml water and 25g SN. But when the time came, I couldn't do it. I'm hoping to try again. But will the solution be ok and still effective if left? This is the second time with SN, and I don't know if I have enough left for a third time to make a solution.

 

[DreamEnd]

Yes it degrades quicker than with time