Mercury *vapor* in CFLs?

Fluorescent bulbs contain mercury so our county recommends disposing them as toxic waste. They can be dropped at the disposal site here for special handling. I had one in a plastic clamshell package that broke before I ever opened it. I took that and a couple of burned-out ones for disposal, and the attendant told me that the mercury is in vapor form and once the bulb breaks it escapes, and I can just throw it in the trash.

First, how can mercury be a vapor at room temperature, and second, is this even true?

A typical cfl contains about 4 milligrams of mercury. That’s not a lot. In fact it’s about 0.3 microliters of mercury.
While mercury is a liquid at room temperature and one atmosphere pressure, like all liquids it has a vapor pressure, and it doesn’t take a very large volume of vacuum to permit 0.3 microliters to evaporate completely.


Check out this map to find your own state’s regulations regarding CFL disposal.

>First, how can mercury be a vapor at room temperature…

Everything has some tendency to evaporate, even solids like metals and diamond. Liquids generally have a much higher tendency to evaporate. Mercury absolutely does evaporate at room temperature. There will be a little cloud or wisp of mercury vapor drifting away from a blob of mercury until it is all gone.

Don’t think that ALL the mercury will necessarily be a vapor at room temperature. It depends on how much vapor there is. Like all substances mercury has a saturation vapor pressure such that at a given temperature an otherwise empty container with mercury ewuilibrated in it will have an atmosphere of mercury vapor having some certain absolute pressure. If there are other things in the container, the fraction of the total pressure representing the mercury will still be that pressure. If the mercury is out in the open so that air keeps washing the vapor away, the mercury will eventually completely evaporate.

You can see Mercury evaporating here:

Hmm. I know that liquids evaporate but I had the impression that the guy was trying to tell me that the mercury was 100% vapor. I wasn’t quite ready to take a chemistry lesson from a guy in a greasy jumpsuit… :wink:

If I can ask a question, so what’s to stop people from just breaking their tubes and just tossing them in the trash saying they’re safe? California wants to phase out the incandenscent, I already seen people just toss the fluorescents in the trash right now and I see more hotdog wrappers thasn tubes in the recycle bin at the Home Depot.

Nothing, except their conscience. What stops people from pouring motor oil down the sewer?

Whats so unconscionable about throwing out a bulb that has mercury in it until it breaks in a landfill (whereupon it would become vapor and quickly not be a problem) or breaking it yourself either by accident or on purpose and just tossing it as opposed to wasting time, effort, fossil fuels (both your own and the truck that picks them up from the deposit location), and the effort of all the bureaucracy required to organize the lightbulb recycling? Eventually that mercury will make it into the atmosphere one way or another. Its a negligibly small amount of gas in a glass bulb.

I just answered the question.
I personally think the amount of mercury in Fluorescent lamps is negligible, but if it’s illegal to throw them in the trash, than doing so should weigh on one’s conscience, regardless of whether one considers the the law reasonable or not.

Practically not much, but in most places, pouring motor oil down the sewer is illegal. Hard to catch someone doing it once, but if a business was doing it regularly, they’d likely get fined.

Ohh… Ok. Thought you were talking about potential damage to the environment being on one’s conscience, not the breaking of a law.

This point is harder to know for sure. Historically, fluorescent tubes generally had a large enough amount of mercury that there would always be some in the liquid state. IIRC they relied on the mercury condensing in the filament to provide a way of vaporizing it quickly to start the lamp (because the lamps needed a higher partial pressure of mercury to light than mercury at room temperature would provide).

But, the environmental ugliness of elemental mercury in household products has driven manufacturers to reduce the amount they use. I don’t know - there may be lamps that have less than saturated partial pressure, so all the mercury is in the vapor state. Or, at least when the lamp is operating, this might be true.

By the way, mercury can exist as little droplets of the element itself in rocks. The droplets are typically in little cavities, and in breaking open rocks sometimes you can see them. I thought this was pretty surprising because of the great length of time this volatile substance would have to stay trapped, but I just read it in a seemingly authoritative book on mineral and rock identification.

I don’t know how aware of these issues that those of you in the US are, but the CFL bulbs are causing some other unwanted side effects in people according to this Canadian TV show…