Movie smoke-The weight of smoke.


I rented a movie called Smoke with Harvey Kietel, William Hurt and Forrest Whittaker. This was a little heralded film, but a sweet, moving film. Mr. Kietel played the role of Auggie Wren a tobacco shop owner and basically a good guy from Brooklyn. Wonderful actor.

Early in the film, the character of Willaim Hurt’s goes into Kietel’s shop for some cigars. Kietel’s shop has a couple of guys who hang out there and talk. Hurt tells a story…

Sir Francis Raleigh bets Queen Elizabeth I that he can measure smoke. In the mist of the tale, the hangers on in the tobacco shop call bullshit, there is no way to measure smoke, that is like measuring air. But…

The story was that Raleigh weighed a cigar (or whatever he was smoking) before he smoked it, smoked the item, and put the butt of the cigar on a scale. Then he subtracted the original weight of the cigar minus the weight of the butt and the answer was the weight of the smoke that was consumed during the smoking.

Could this be true? Or just an inaccuracy?


It cannot be accurate. When something burns in air it combines with oxygen. The weight of the smoke must include the mass of what is burnt plus the mass of oxygen consumed.

A remeber a nice school experiment that I later demonstrated to a young student. Take some fine iron wool. Weigh it. Set light to the iron wool with a blow torch and make sure it gets plenty of air - it gives off plenty of smoke. Ask: should the wool weigh more or less after combustion. The uninitiated generally answer “less”. In fact it weights significantly more. Nice little home experiment, although you must take great care!

On the other hand, Raleigh might have won his bet against the best scientific brains of the time. No-one knew about oxygen nor properly understood combustion, nor would anyone until about 150 years later. Fire was once understood to be the release of something called “phlogiston”, and in those terms it would be very reasonable to believe that the amount of matter in the smoke would equal the amount of matter in the fuel.