It is a big hit in any chemistry class: the woosh bottle. Take a 25 liter polycarbonate water cooler water container, add 10 ml of ethanol or isopropanol (rubbing alcohol), rinse and then add a burning match. Amazing how little fuel can produce that much of an ignition. Youtube has dozens of clips with all sorts of variations. In a recent contribution to woosh bottle research researchers at the University of Dubuque report that contrary to expectation isopropanol does not just combust to water and carbon dioxide. Instead GC analysis reveals a host of hydrocarbons such as naphtalene and styrene. Main cause: the alcohol is added in excess and the combustion is incomplete. Also, a lot of the energy released in the combustion goes into vaporizing more alcohol thus slowing down the reaction.
The researchers propose that the bottles should be discarded of as chemical waste because many of the chemicals they found are nasty polycyclic aromatic hydrocarbons. Please disregard this advice: the levels are in the microgram per ml range. The same researchers also advise blast shields to protect the students in class-room demonstrations. In 30 or-so youtube demonstrations in front of students from the age of 7 NOT ONE blast shield was spotted, this blog can report.
And as for the incomplete combustion? That does not come as a surprise for the youtube researchers in video number two. According to these demonstrators using less alcohol rather than more gives a better display. The guys in video number 3 solved the problem of incomplete combustion: they made pure oxygen first in a potassium iodide / hydrogen peroxide reaction. Pure rocket science.