The tooth is warmed to 37C in a water bath. Ultraviolet light is used with a fluorescent screen to show the "mercury vapour". The vapour absorbs the ultrviolet light, which then shows on the flourescent screen. For those who have seen the video it looks pretty conclusive. That is until you start to look at some of the science behind the claim.
Mercury vapour is not the only gas that absorbs ultraviolet light. Water vapour just happens to be another gas that absorbs UV light strongly.
The gas from the tooth rises, whereas mercury is very heavy. Jim Laidler provided the following calculations:
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 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:
200 grams per mole / 25.452 liters per mole = 7.86 grams per liter
In layman's terms, what Mr. Laidler is showing is that mercury vapour is much heavier than the normal air, where water vapour is lighter. If this was mercury, the gas would sink, not rise. If we have a rising vapour coming from a tooth in heated water, then what we are seeing is water vapour, NOT mercury vapour.
If the anti-amalgam proponents are peddling false information about what gas is rising from the tooth in their video, what else are they saying that is untrue?
"There is only one truth. How we interpret that truth is called belief."
"The presence of belief, does not indicate the existence of truth."