Re:Deliquescence vs. hygroscopy
Dear Shanks: I guess my chemistry must be at least twenty five years older than yours, and my recollection of it less than half yours. I can't remember the product I made that would completely turn to liquid if left uncovered. I had totally forgotten "hygroscopy". Looking at dictionary, I now have impression that things like sugar and salt are merely hygroscopic. Deliquescence has to be rather uncommon. Link below gives complete explanation.

http://antoine.fsu.umd.edu/chem/senese/101/compounds/faq/why-hygroscopic.shtml