The evaporative rates of two drops of mercury at room temperature are determined experimentally and theoretically. The resulting mercury vapor levels are estimated and measured, compared with the OSHA permissible exposure limit, and found to be small by comparison.

1.
CRC Handbook of Chemistry and Physics, edited by D. R. Lide (CRC Press, Boca Raton, FL, 2001), 82nd ed., p. 4-19.
2.
The same words are to be found in the 1965/66 edition, CRC Handbook of Chemistry and Physics, edited by R. C. Weast (Chemical Rubber Co., Cleveland, 1965), 46th ed., p. B-121.
3.
29 CFR [Code of Federal Regulations] 1910.1000, revised 1 July 1999. The corresponding NIOSH ceiling is a factor of 2 lower, according to the NIOSH Pocket Guide to Chemical Hazards [Publication No. 97-140] (US GPO, Washington, 1997), p. 192.
4.
Each drop was in an open plastic container of height 1.3 cm, length 4.5 cm, and width 3.3 cm.
5.
To assess the accuracy of the weighing procedure, controls, such as an empty container, were also weighed each time. We used the observed, assumedly spurious variation of control masses of a few tenths of a milligram to correct the measured masses of the drops and obtained only slightly modified rates of mass loss, 1.6 and 6.0 μg/h, respectively.
6.
R. B. Bird, W. E. Stewart, and E. N. Lightfoot, Transport Phenomena (Wiley, New York, 1960), p. 502.
7.
Reference 6, p. 528.
8.
J. O. Hirschfelder, C. E. Curtiss, and R. B. Bird, Molecular Theory of Gases and Liquids (Wiley, New York, 1964), p. 539.
9.
Reference 6, p. 511.
10.
R. C. Reid, J. M. Prausnitz, and B. E. Poling, The Properties of Gases and Liquids (McGraw–Hill, New York, 1987), 4th ed., p. 582.
11.
Reference 10, pp. 583, 733–734.
12.
The air pressure Pa was not monitored during the experiment. The average value of Pa should be reduced from the sea-level value by an estimated 4.6% and D should be increased by the same amount considering the elevation of 1300 ft where the experiment was performed. However, because this correction does not affect the mass loss rate of the smaller drop to the reported two digits and affects that of the larger drop to only one unit in the second digit, it is neglected.
13.
Reference 8, pp. 1111–1112, 1126.
14.
Reference 10, p. 583.
15.
The Hg pressure was obtained from the formula log P=−3212.5/T+7.150, where P is in units of kPa. See Encyclopedia of Chemical Technology, edited by J. I. Kroschwitz and M. Howe-Grant (Wiley, New York, 1995), Vol. 16, 4th ed., p. 213. A nearly equivalent formula, when corrected, is given by H. E. Stokinger, “The metals,” in Patty’s Industrial Hygiene and Toxicology, edited by G. D. Clayton and F. E. Clayton (Wiley, New York, 1981), Vol. 2A, 3rd ed., p. 1771.
16.
This formula appears in a different notation in the Encyclopedia of Analytical Science, edited by A. Townshend (Academic, London, 1995), Vol. 6, p. 3753.
17.
We ignored the space occupied by the furniture.
18.
Handbook of Heating, Ventilation, and Air Conditioning, edited by J. F. Kreider (CRC Press, Boca Raton, FL, 2001), p. 6-3.
19.
An early study of a mercury spill in a carpeted room showed a great reduction in mercury vapor levels with “open ventilation.” See
W. B.
Eames
,
J. D.
Gaspar
, and
H. C.
Mohler
, “
The Mercury enigma in dentistry
,”
J. Am. Dent. Assoc.
92
,
1199
1203
(
1976
).
20.
Mercury in the Environment: Geological Survey Professional Paper 713 (US GPO, Washington, DC, 1970), pp. 37, 59.
21.
Handbook on the Toxicology of Metals, edited by L. Friberg, G. F. Nordberg, and V. B. Vouk (Elsevier/North-Holland, Amsterdam, 1979), p. 509.
22.
W. F.
Fitzgerald
, “
Is Mercury increasing in the atmosphere? The need for an atmospheric Mercury network (AMNET)
,”
Water, Air, Soil Pollut.
80
(
1/4
),
245
254
(
1995
).
23.
Reference 15, Encyclopedia of Chemical Technology, p. 220.
24.
Environmental Health Criteria 118: Inorganic Mercury (World Health Organization, Geneva, 1991), p. 109.
25.
“A 5-lb bottle of elemental mercury was dropped by an employee of the University of Virginia’s Hospital Supply Storeroom … The Office of Environmental Health and Safety was called to pick up the waste and survey the damage … The airborne concentration of mercury vapor was measured [by the State Department of Emergency Services] …, and found to be above 0.3 mg/m3 … The following day, the Department of Emergency Services helped clean up the remaining mercury … Testing showed that levels were then below 0.1 mg/m3” [
D. N.
Easton
, “
Management and Control of Hg Exposure
,”
Am. Lab. (Shelton, Conn.)
20
(
7
),
66
70
(
1988
)].
26.
Jerome 431-X Mercury Vapor Analyzer: Operation Manual (Arizona Instrument LLC, Tempe, AZ, 2000). At the low levels of 25 and 10 μg/m3Hg, the Certificate of Instrument Calibration (10/25/02) indicates a precision of 5 μg/m3.
27.
Reference 2, p. B-121. This statement was made at a time when “the maximum allowable concentration of mercury vapor in the air [was] set at 0.1 mg/m3” (p. B-121), the same as the present OSHA limit.
28.
K. Lumley-Sapanski (private communication, 24 October 2002).
29.
“Mercury in the environment,” U.S. Geological Survey Fact Sheet 146-00 (U. S. Dept. of the Interior, U. S. Geological Survey, Reston, VA, October, 2000).
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