T  get some epsom salts and put on a tray in the oven for about an hour or cook in a pot on a hotplate until you see it turn greyish. Doing so makes anhydrous magnesium sulphate - mix some of this magnesium sulphate with your acetone until the residue no longer forms clumps then you should have totally anhydrous acetone.

You can get acetone, epsom salts and fumaric acid from ebay UK quite cheaply.