RadicallyStabilized - 3-10-2018 at 06:27
Hello,
hobby chemist with a small lab here... long time reader, first time poster 
Can anyone tell me how long Brady's reagent (made from 2,4-Dinitrophenylhydrazine, ethanol or methanol, and sulphuric acid) can be stored without
becoming useless? I haven't been able to find something conclusive online, only some confusing information:
Stable for 10 days: http://media.rsc.org/Microscale%20chemistry/Microscale%2046....
Should be discarded after opening: http://blog.philipharris.co.uk/news/bradys-reagent-safer-alt...
36 months: https://www.lobachemie.com/Clinical-Reagents-Solutions-for-M...
Some MSDS say it's stable indefinitely.
Most recipes seem to specify sulphuric acid, but I've also found some that use phosphoric acid. Is there any advantage in using H3PO4 instead of
H2SO4?
Thanks