eugeneoregon
Active Member
Here is data on a short path run in my hobby short path distillation rig. I started with Nalgene hose from pump to rig but could not pull any sort of hard vacuum. I discovered, after buying $17 per foot Nalgene, that any polymere is not suitable for use as primary vacuum lines for deep vacuum molecular short path distillation. Nalgene is now only used in very short pieces to connect, with stainless steel bellows and fixtures.
Distillation is carried out at approximately 8-10 microns and this value varies up to 35 microns as temperature setting change and a new vapor load is created. Then after several minutes the vacuum pulls down again to 10 micron or less. The interesting thing is that Pubchem (like Wikipedia only peer reviewed/piblished government run chemical database) lists THC-9 as have a boiling point of 200C at .02 mmHg. mmHg means millimeters of mercury and is also said as "Torr".
.02 Torr is also said 20 microns and on the video I speak of microns because I got used to thinking microns. As you can see the boiling flask heating mantel, sensor on side of boiling flask, shows 173C while the vacuum is pulled down to 8-10 microns. This data suggests that either an azeotrope of some sort alters the boiling point this much or the deeper vacuum of 10 microns vs. 20 microns is the reason I see the data I do. This is a prototype unit and I have yet to get the proper ground glass head thermometer. In its place is a partial immersion thermometer not meant for this short path head. I used it because I was impatient and this completes the vacuum but the head readings are a bit meaningless since the thermometer is calibrated for partial immersion only.
Distillation is carried out at approximately 8-10 microns and this value varies up to 35 microns as temperature setting change and a new vapor load is created. Then after several minutes the vacuum pulls down again to 10 micron or less. The interesting thing is that Pubchem (like Wikipedia only peer reviewed/piblished government run chemical database) lists THC-9 as have a boiling point of 200C at .02 mmHg. mmHg means millimeters of mercury and is also said as "Torr".
.02 Torr is also said 20 microns and on the video I speak of microns because I got used to thinking microns. As you can see the boiling flask heating mantel, sensor on side of boiling flask, shows 173C while the vacuum is pulled down to 8-10 microns. This data suggests that either an azeotrope of some sort alters the boiling point this much or the deeper vacuum of 10 microns vs. 20 microns is the reason I see the data I do. This is a prototype unit and I have yet to get the proper ground glass head thermometer. In its place is a partial immersion thermometer not meant for this short path head. I used it because I was impatient and this completes the vacuum but the head readings are a bit meaningless since the thermometer is calibrated for partial immersion only.