Silly Mac OSX.
Clean up memory cache easily this way:
Add the following entry in your root's crontab:
# Clean up memory
30 * * * * /usr/sbin/purge &
Use at your own risk, but I have not had issues with it.
If you don't know how to update your root crontab, well, then you have no business running this. Use some 3rd party graphical app or something to clean up.
FYI: Some people are having issue with Chrome and Flash and other programs not "letting go" of reserved memory, after use. This will help alleviate the issue. Developers are arguing over it's use, claiming memory management is just fine in OS X 10 Mavericks and later. I beg to differ as I have seen memory run out several times myself with using Chrome web browser and it not letting resources go.
You can read more about it, here: