A chemistry professor that I was acquainted with did this as one of his lecture demonstrations. Shakhashiri (and he's still doing it - http://scifun.chem.wisc.edu/BZSPresentations/Presents.html Once Upon a Christmas Cheery, In the Lab of Shakhashiri is going on its 47th year!). https://www.youtube.com/watch?v=_tsgh_T59gE has what you are looking for (at 3:42 though you'll likely want to start a tad bit earlier).