A pre-trap is used to remove the bulk of the solvent from the solid product, and this piece of apparatus is shown in Figure 3a.
Close taps X & Y and evacuate the trap via tap Y. Place the trap in the polystyrene igloo and surround it with liquid nitrogen.
Turn off the nitrogen supply to flask C and attach the flask to tap X of the pre-trap. Evacuate the tube and then open the side-arm tap slightly and swirl the flask gently. Next, lower it into a bath of warm water (about 45°C).
Take care to evaporate the solvent in a controlled manner by carefully controlling both the side-arm tap and the warmth from the bath; you should continue until only solid product is left.
Clamp the flask, close the side-arm tap and close taps X and Y on the pre-trap.
Dismantle the pre-trap by removing the liquid nitrogen bath and then gently opening the trap to air. When the trap has warmed up, dispose of the organic waste in the appropriate residue bottle.
Further dry the product using the vacuum line directly for at least 10 minutes as it is essential that the sample be thoroughly dry before the vacuum sublimation step.