I don't fully trust any solvents as they are supplied, even if they do not leave a visible residue. Considering how inexpensive a ground glass distillation kit is now [costing about as much as a few hours at a nightclub, if bought from china on a popular auction site] I think the more serious of us should get used to distilling our solvents prior to first use.
The apparatus should have a stand to hold it, if using bare metal clamps remember heating glass expands, a tight bare metal clamp can easily break heating glass. The boiling flask can be heated in an oil bath, itself heated with an electric burner. Some boiling chips must always be added before heating or reheating. The apparatus should have a water-jacketed condenser which can be cooled by gravity feed between two large buckets, I put the output bucket half a meter lower than the source bucket and start the flow by connecting a funnel and raising it until the siphon effect will keep the flow going.
Water distillation lowers the temperature of a solvents boiling point for most solvents [azeotropic distillation]. By adding an equal volume of water, the boiling point of the solvents we pull with is reduced to 80-96º and the water and solvent separate again in the receiving flask.
Acetone and methanol do not carry water over and water can be added to allow the last of the solvent to safely distill over without overheating. Butanone, ethanol, and isopropanol will carry some water over but in these cases it will stay dissolved.
When distilling heavier fuels and naphthas with water its best to stop the distillation when the temperature at the distillation head reaches 98º because at 99-100º components that are very slow to evaporate will distill over.
I fully understand why the majority of people will never go this far, but it surprises me that almost no one does.
Why did you take chemistry in high school, if not to make drugs!
