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 Subject: mercury evaporation Category: Science Asked by: max22-ga List Price: \$20.00 Posted: 11 Jul 2004 15:50 PDT Expires: 10 Aug 2004 15:50 PDT Question ID: 372824
 ```How long will it take 1/2 a gram of liquid mercury to evaporate completely at 68 degrees Fahrenheit? How long will it take at 70 degrees Fahrenheit?```
 Subject: Re: mercury evaporation Answered By: sublime1-ga on 11 Jul 2004 18:07 PDT Rated:
 ```max... It would take 8928.5714285714285714285714285714 hours for .5 grams of mercury to evaporate completely at 68F degrees, assuming an evaporative surface area of 1 square centimeter. This is based on the volatility of mercury, which is the measure of how quickly it evaporates, and is 0.056 mg/h.cm², or .056 milligrams per hour per square cm, at 68F or 20C: "Given that the volatility of mercury at a temperature of 20°C is 0.056 mg/h.cm²" From a document titled 'Code of Practice Mercury Housekeeping', page 13, on the United Nations Environment Programme - Chemicals: http://www.chem.unep.ch/mercury/2003-ngo-sub/Eurochlor/Code%20of%20practice%20Hg%20housekeeping%20(Env%20Prot%2011).doc The chart just below this statement, in the link above, indicates how mercury evaporates more quickly in proportion to the increase in surface area exposed, so .5 grams in a single globule won't evaporate nearly as fast as the same amount dropped onto the floor and scattered into multiple tiny globules. It illustrates how 1000 tiny droplets, vs one droplet of equal volume, will increase both the evaporative surface area and the rate of evaporation by a factor of 10. Now 68F = 20C, and 70F = 21.1111111C, which is a very small increase in terms of the volatility of mercury, so this increase in temperature would take only slightly less time. I am unable to determine the exact difference since I was unable to find a formula for the volatility of mercury at the temperature of 21C. Such formulae are typically given a standard format based on normal room temperature. Out of 8928 hours, I would guess it would take just a few hours less to evaporate at 70F. The change in the volatility of mercury is nicely illustrated in the charts shown on page 3 of this PDF file, titled 'Release of Mercury From Broken Fluorescent Bulbs' from the website of the State of New Jersey: http://www.state.nj.us/dep/dsr/research/mercury-bulbs.pdf As you can see, there is no significant difference in the volatility of mercury between 40F and 60F. At 85F, however, you can see that the evaporation occurs almost twice as quickly as it does from 40-60F. I hope this satisfies your needs in asking the question, as I sincerely doubt that a more accurate answer can be provided. Please do not rate this answer until you are satisfied that the answer cannot be improved upon by way of a dialog established through the "Request for Clarification" process. A user's guide on this topic is on skermit-ga's site, here: http://www.christopherwu.net/google_answers/answer_guide.html#how_clarify sublime1-ga Additional information may be found from an exploration of the links resulting from the Google searches outlined below. Searches done, via Google: mercury evaporation ://www.google.com/search?q=mercury+evaporation "mercury evaporates" ://www.google.com/search?q=%22mercury+evaporates%22 mercury "rate of evaporation" ://www.google.com/search?q=mercury+%22rate+of+evaporation%22 "volatility of mercury" temperature ://www.google.com/search?q=%22volatility+of+mercury%22+temperature```
 max22-ga rated this answer: `very helpful`

 Subject: Re: mercury evaporation From: purkinje-ga on 12 Jul 2004 10:29 PDT
 ```The mercury at 70 degrees would evaporate in 20/21.1 of the time of the evaporation at 68 degrees, i.e., 8459 hours. Just for your interest, perhaps, the danger of breaking neon lights is that the little drop of mercury in the tube (which emits uv light when a charge is run through the light, and that uv light is absorbed by the phospholuminescent interior of the glass) is totally evaporated, and mercury causes neurological damage when ingested/inhaled.```
 Subject: Re: mercury evaporation From: keningersoll-ga on 13 Jul 2004 16:22 PDT
 ```One minor point. The surface area is assumed to be constant whereas the evaporation will cause it to deminish over time. This means that rather than being a linear function, the evaporation will be an exponential. Even so taking the 8kHrs as the half life of the oringal sample, the danger is still obvious. Ingestion via fish contaminated with methyl mercury presents more of a danger than inhalation and should be avoided especially in young children.```
 Subject: Re: mercury evaporation From: taiga-ga on 14 Jul 2004 08:57 PDT
 ```I don't think the 20/21.1 ratio is accurate. If this were true, there would be an error at 0 degrees C.```
 Subject: Re: mercury evaporation From: purkinje-ga on 14 Jul 2004 11:17 PDT
 ```Good point taiga. It would all have to be converted to kelvin. Also, good point kiningersoll-- as the drop gets smaller, it evaporates faster relative to its mass (because of surface area/volume ratio). So even my temp ratio is only an approximation.```