Flame drying

There are different ways to prepare the glassware. An easy way is to assemble the set up and then purge it with an inert gas for some time. This procedure will remove the majority of the air, but it will leave behind the moisture (hydroxyl groups) and air absorbed on the glass itself. In order to remove it, the glassware has to be heated with a heat gun (or Bunsenburner) while purging it (Make sure that you remove all flammable materials from the area to prevent fires. The heat guns in the laboratory are industrial scale heat guns. They allow temperatures up to 500^oC. If you are done heating the glassware, you have to switch to cooling in order to cool down the wire inside. If you fail to do it, this wire will burn and the heat gun will break). This technique works for less sensitive materials.

In this lab, you will remove air and moisture from your glassware by heating it under vacuum at a Schlenk line. This is usually more efficient in terms of removal of surface materials. It is important that you do not heat the glass joints and the stopcocks directly with the heat source. They will undergo slight deformation and start to leak air in. Also, the high vacuum grease that you will use melts at ~250 ^oC. It will get sucked into the setup and your product will be contaminated with it. The glassware should be hot to the touch and allowed to cool down under vacuum before refilling it with inert gas (Careful: Check who else is connected to the inert gas supply!). This process should be repeated at least once.

For extremely sensitive applications, the glass surface can be passivated with chlorotrimethylsilane.