Removing trace amounts of water from agricultural grade anhydrous ammonia Agricultural grade anhydrous ammonia (liquefied gas) contains 2000 ppm $\ce{H2O}$. What would be the process to remove this water to obtain refrigeration grade (&lt;100 ppm $\ce{H2O}$) anhydrous ammonia?
Calcium oxide can get water down to 4ppm in anhydrous ammonia according to http://www.google.com/patents/US4075306.