gravityzero - 3-7-2013 at 10:07
I have a few drying questions that I'm sure others know good answers to.
Why do some preparations call for using a dry solvent, when the step involves combining the solvent with an aqueous layer?
One time I was using acetone in an attempting to purify a dirty alkaloid. The process called for dissolving the impure alkaloid in a small amount of
purified water, just enough water to dissolve it. Then the mixture is flooded with dry acetone, which makes only a pure alkaloid crash out.
Apparently the small amount of water traps most of the impurities. Acetone straight off the shelf would only contain trace amounts of water, so why
would I spend extra time and effort removing it?
I have another question. I usually dry the solvent with a recommended drying agent, say calcium chloride. I bake the cacl2 in an oven for an hour or
so, powder, then add to the solvent and stir.
Is it imperative to distill the solvent after drying or would a simple filtration suffice?
gravityzero - 3-7-2013 at 17:12
WoW. I guess I never thought about it like that. Thanks so much for all the help. It is really appreciated. 
bfesser - 3-7-2013 at 17:27
I would guess that your procedure calls for dry acetone because it would be slightly more effective at 'stealing' the water from your alkaloid (sorry,
too tired for a proper explanation). Filtration should suffice for your purposes, as long as the filtrate is clear.
gravityzero - 3-7-2013 at 17:46
Thanks so much for the comment. Sometimes there are things that I understand, but just need some confirmation.
Sometimes I read a procedure and wonder if I know more than the person who wrote it.
The real complication is I don't have much experience to back me up.