Sciencemadness Discussion Board

Drying Crystals

sternman318 - 27-6-2011 at 08:17

So I did a really poor recrystallization of ammonium nitrate from some ice packs ( the whole thing crystallized into a big chunk when it cooled haha). I got some of the brown surfactant gunk out, but I will recrystallize some of it if I really want pure stuff. But, now I have a mass of crystals which seem to be retaining some water. So i have two questions

1. If I cooled the crystals and rinsed them with cold distilled water, would I have to worry about losing lots of crystals? I am thinking this may help remove some of the last bits of gunk that might be present

2. How do i go about driving out the rest of the water? If I put them in a beaker and heat them on a low heat on a hot plate, do you think that would drive out the moisture?

Bot0nist - 27-6-2011 at 09:10

Since NH<sub>4</sub>NO<sub>3</sub> is very soluble in water you would lose a lot by rinsing with water. It is also very hygroscopic, so once it is dried you will have to put it in a very sealed container to keep it that way.

My personal method for drying is:

Crush to a fine powder with a rolling pin. Spread out over the bottom of a pyrex dish.

Put in oven at 135F for 3 hours.

Re-crush and 'fluff' the powder to exposes any moisture that may have been trapped by slight melting in the oven.

Put in a 1 gallon sealed bag with an excess of a suitable dry desiccant over night.

Store in an air-tight container.