Confessions of a Quackbuster

This blog deals with healthcare consumer protection, and is therefore about quackery, healthfraud, chiropractic, and other forms of so-Called "Alternative" Medicine (sCAM).

Wednesday, April 06, 2005

"Smoking Teeth" - the truth gets "smoked out"

"Smoking Teeth" - the truth gets "smoked out"
by James Laidler, MD

Many of you have seen the shocking video of "mercury vapor" being released from an extracted tooth with a well-aged amalgam restoration ("filling") (if not, see: ). In this video, the tooth is warmed to body temperature (37 degrees Celsius) in a water bath and the "mercury vapor" coming off of it is made visible by holding the tooth in front of a fluorescent screen and illuminating it with ultraviolet light. The ultraviolet light, strongly absorbed by the "mercury vapor", shows the shadow of a vapor plume rising from the tooth.

Ever since I saw the video, I felt that there was something wrong with it. At first, I realized (as I was watching it) that water vapor ALSO strongly absorbs UV light. However, this does not rule out mercury vapor.

Finally, it hit me (after over two years). Watching the video, it is very clear that the "vapor" is rising. This, you might think, is to be expected - after all, it was warmer than the room temperature.

However, mercury has a very high molecular weight (200 grams per mole) when compared with the nitrogen (28 grams per mole) and oxygen (32 grams per mole) that make up the atmosphere. Water, on the other hand, has a molecular weight of only 18 grams per mole.

Now, bear with me.

When molecules vaporize, the volume they fill depends on the number of molecules and their temperature. At standard temperature and pressure (STP - one atmosphere and 0 degrees C), that volume is 22.414 liters per mole. At room temperature (20 degrees C), the volume expands to 24.055 liters per mole. (at 37 degrees C - body temperature - it is 25.452 liters per mole)

Whether a gas will rise or sink depends on the density difference (if any) between that gas and the surrounding gas. Hot air rises because the same mass of "air molecules" expands to fill a larger volume. Since density is mass divided by volume, the hot air is less dense than the surrounding cooler air and so rises.

Since air is a mixture of 78% nitrogen and 21% oxygen (and a few other gasses), it has an "averaged" molecular weight of 28.8 grams per mole. Therefore, its density at room temperature is:

28.8 grams per mole / 24.055 liters per mole = 1.20 grams per liter

Water vapor at 37 degrees C has a density of:

18 grams per mole / 25.452 liters per mole = 0.71 grams per liter

Water vapor at 37 degrees C will rise in room temperature air, as a result.

Mercury vapor at 37 degrees C has a density of:

200 grams per mole / 25.452 liters per mole = 7.86 grams per liter

So, if what we saw was actually mercury vapor coming off those teeth, and not just water vapor, it should have been SINKING rather than rising - even at 37 degrees C. Therefore, the video DOES NOT show mercury vapor rising off the tooth, only water vapor.


Next slide, please.

Jim Laidler, MD
Portland, Oregon USA