Wondering what those splotches are where the ink started running on the first panel? Guess what caused that.
Welp, this is how my day has gone. Pretty much all week, really. I thought I had a pretty good grasp on thermodynamics, but using the rotavapor has made me question everything I’ve ever learned.
I understand why, when the vapor really gets going, it warms up the “cone of cold” and causes an eruption of dry ice and acetone.
I understand why the distillate spontaneously freezes every now and again.
But there seems to be no rhyme or reason to when the concentrate boils over or not. I crank the temperature down to 4 degrees C, I dump ice in the water bath, and yet every time it boils out of control for about 30 minutes and then it calms down forever.
At first I thought, well duh, I boiled all the acetonitrile off so now it’s behaving. But lo, I brought the concentrate down to the “stable state,” turned the machine off to take lunch for an hour, came back, started it up again, and oh boy it just started boiling all over again. If I ever stop it or take any sort of break during this “stable state,” picking up where I left off means starting back at the beginning.
Thermodynamically, I cannot explain this. Therefore, I have decided that there’s something wrong with the vacuum pump which means it needs to warm up for a half an hour before it pulls a stable vacuum in the flask. I tried to test this, but then I realized I had to turn the pump off to pour my liquid into the flask and restart it… but I will find a way to test this hypothesis! Mark my words!