Anyone that has ever tried to condense their own NH3 will insist that the pre-cooler is a must, unless they have some state of the art condensor system, or lots of cash for the pounds and pounds of dry ice needed without the pre-cooler.
Without the pre-cooler or drying tube, if you are using just dry ice, you will no doubt clog your line with the excess water carried in the ammonia fumes as it freezes due to the extreme cold. For this reason you want both the drying tube and the pre-cooler.
Why? Because the pre-cooler will cool the warm/hot gasses considerably, and thus condense most of the water moisture. Then, run this up-hill and through a drying tube to catch the remaining.
Why not use the drying tube first? Or just a drying tube and no pre-cooler? Obviously there is a lot of moisture, and your drying tube would become fucked pretty quick.
Post 485647 (https://www.thevespiary.org/talk/index.php?topic=5171.msg48564700#msg48564700)
(TrickEMethod: "30min/$40 - NH3 generator!", Chemicals & Equipment) is worth checking out--it's pretty fucking ingenious if you ask me. It's definately worth taking a look at.
RV