[Emmas151]

Basically I have to make an ammonium molybdate solution, but I won't be able to filter it for about 72 hours. I'm worried that will be too long based on the nature of the solution. The USP method says "Allow to stand for 48 hours, and filter through a fine porosity, sintered-glass crucible. This solution deteriorates upon standing and is unsuitable for use if, upon the addition of 2 mL of dibasic sodium phosphate TS to 5 mL of the solution, an abundant yellow precipitate does not form at once or after slight warming. If a precipitate forms during storage, use only the clear supernatant" The way I'm reading this, it seems like it deteriorates over a longer period of time, not in a matter of days, and if it does form precipitate within the few days I haven't filtered it, it should be ok.....right???

[shchavel]

Hello Emmas151, I think that you're right. But to be 100% sure - use sensibility test that ordered by USP

This solution deteriorates upon standing and is unsuitable for use if, upon the addition of 2 mL of dibasic sodium phosphate TS to 5 mL of the solution, an abundant yellow precipitate does not form at once or after slight warming.

You should check this solution every time before use, unless you carry on some risk analys and profe exact storage time for you solution in your lab prepared with your reagents and ex.