In an ongoing project to adapt microscale techniques to our
Basic Organic Chemistry Course we needed a simple, inexpensive
and highly efficient vacuum distillation apparatus. Several reactions
give liquid products (usually in the 0.2-0.5 mL range) suitable
for purification by distillation. Since common microscale equipments
were rather inefficient and retained a large fraction (0.07-0.14
mL) of the material after completed distillation we designed a
new apparatus. Several test runs with diethylmalonate in our equipment
gave a good yield of distilled material and only a small amount
remained (approx. 0.025 mL). The apparatus consists of a tube
with an NS 10 joint, bent twice and fused to a water cooled condenser.
The tube is then connected to a vacuum pump or water aspirator.
The distillate is collected in a 1.75 mL glass vial that is tightened
with an O-ring or a rubber gasket simply made from a rubber sheet
(1-3 mm thick) with a corc-borer. This apparatus has been tried
in our student laboratories with very good results. The distillation
is fast and efficient and the equipment is very easy to handle.