mayko - 5-4-2016 at 19:21
Some weeks ago, a friend of mine dropped off an herbal vaporizer, of the sort pictured here. He was unsatisfied with its performance, but suggested that I turn it into a DIY MelTemp! It's not hard to cobble one together from common lab equipment but I thought it would be nice to have a dedicated apparatus.
My first design was to pack the heating cup with copper powder for good thermal conductivity, and then nestle a glass vial in it, containing mineral
oil. A test tube was partially submerged in the oil as a heating chamber. Then a thermometer with a sample was lowered into the heating chamber, the
device was turned on, and the sample observed by eye (I could have added my USB microscope).
This design seemed to have about a 5 degree C cool bias: I tested vanillin (mp 80-83C) and naphthalene (mp 80.2C) and both melted with the thermometer
reading ~76C. I suspect this is due to thermal inertia of the thermometer bulb, which is much larger than the sample.
In the second design, I skipped the test tube and submerged the sample and thermometer in the oil itself. This gave a reading of 80-81C for vanillin,
but is a little messy and inelegent. I would prefer something more like a metal cylander, with a slot machined in for the sample and thermometer, and
a glass face to look through. Also, the device will need stabilizing, as it is quite topheavy with the thermometer in it.
On the plus side, the original device was built with flickering colored LEDs, so my measurements will be extremely groovy.
