I'll throw my 2cents out there before this gets locked in the interest of harm reduction...
First, you probably got ripped off. Never buy a bag of crushed Xanax, your bag is 99% filler, and if it actually IS crushed Xanax, there is no way to tell how much you're taking.
I would advice against taking it at all, but, since you're going to, Xanax has a rather distinctive taste and lingering aftertaste.
Never buy from whoever you bought from again.