Its definitely still active, no worries.
Borohydride likes to clump together but that doesn't diminish its activity to a noteable extent.
So if you can get it out, just hack off a piece that amounts to your needs when you weigh it(you probably took too much), and simply apply pressure in
a piece of suitable paper, and it will be powdered again very easily.
If it is for longer in that state now, use a thick paper and smack it with a hammer.
Thats what I do.
And that is actually also what is recommended in case you have the same problem with LiAlH4 and want to powder it(just in two ziploc bags of course!
 ).
If you want to be sure that it still works, you can use 5% more but I can assure you, when that stuff is less than 5 years old, that it will
definitely not lost more than maybe 1% or at worst 2% of activity, and even that is a number I would doubt.
NaBH4 is remarkable stable to air humidity, because in that case its own basicity dominates over the tiny amounts of water, and we know that base
stabilises borohydride.
Its just the other way round if the water is dominant, i.e. in solution.
But basified NaBH4 solutions remain stable for years, just so you get a different perspective on the remarkable stability of borohydride.
You can titrate it if you remain insecure about its activity though... but I can assure you it will still be good, much better than you would expect.
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
