Homebrew PCBs

Hi all,

When I bought the Ferric Chloride, I bought 2 pounds, enough to make 
a gallon, however, my tank only holds a half gallon.  So, I mixed up 
a half gallon then put the remaining powder in a plastic container.  
I had the lid off of it for about 6 hours or so though.  

I noticed that it was taking on moisture which sort of freaked me 
out so I put the lid on it.  This was two days ago. Today, I looked 
at the powder and it appears to have dried up a bit and is a little 
disscolerd on the top, but looks normal otherwise.

Has anyone else had this happen and is it anything to worry about?  
Should I do something else besides keeping it in that plastic 
container?

TIA

Chris