School Science Lessons
2018-10-13
Please send comments to: J.Elfick@uq.edu.au

Mercury
Table of contents
See: Mercury Elements, Compounds, (Commercial)
Mercury in barometers and thermometers: 1.9
Mercury - Biology: 3.2.0
Mercury - Chemistry, Geology, Safety: 3.0.0
Mercury - Physics, Astronomy, Weather: 3.3.0

3.2.0 Mercury - Biology
Mercury and dental amalgam: 3.0.0
Experiments
Body temperature, (clinical thermometer): 5.17
Measure osmosis: 9.12.0
Respiration of flower heads over mercury: 6.6.2
Respiration of soaked peas over mercury: 6.6.5
Root pressure, Fuchsia, busy Lizzie: 9.3.15
Tests for proteins, Millon's test: 16.6.7
Transpiration by leaves exerts suction: 6.2.13

3.3.0 Mercury - Physics, Astronomy, Weather
Atmospheric pressure, barometer, Torricelli: 13.1.0
Calomel half cell: 15.6.16
Capillarity, capillary action, capillary rise in wicks: 19.3.0, (See 4.)
Capillarity: Mercury
Thermometers: 22.7.01
Diffraction grating, spectroscope: 27.35, (See 2. mercury lamp)
Distance and diameter of planets: Table 36.25, (See: planet Mercury)
Drops and films, wetting: 19.0.1
Dry cell torch battery, (flashlight battery): 33.4.2
Electric light bulb, incandescent filament lamp, light globe: 4.65, (See 3.
mercury lamp)
Electrical conductivity of a substance: 15.59.0
Fluid expansion: 23.3.02
Fluorescent lamp: 4.117, (mercury vapour)
Force pump: 12.4.4, (column of mercury)
Immersion oil: 1.14 (Mercury e line)
Lift pump: 12.4.2, (column of mercury)
Mercury, 1 mm mercury, Pressure definitions: 12.1.01
Mercury barometer: 4.229
Mercury battery, mercury cell, mercuric oxide battery: 3.3.7
Oscillating mercury: 4.222
Pressure definitions: 12.1.01
Resistance: 32.3.02, (See 10. superconducting Hg)
Solar system model, astronomical unit, (AU): 36.25, (Planet mercury)
Standard temperature and pressure, density of gases: 20.0.6
Superconductors: 31.4.6
Thermometers and temperature: 22.7.0
torr, Pressure definitions: 12.1.01
Weston Standard Cell, Weston cell: 33.3.01

Experiments
Attraction and repulsion of parallel electric currents: 30.3.11
Barlow's wheel: 29.2.6.9
Barometer in a bell jar: 13.1.02
Birefringent mica: 27.188, (mercury light)
Coefficient of expansion of liquid in flask and U-tube: 23.2.9
Crookes' radiometer: 20.4.2
Dancing spring, electric current in parallel coils: 30.3.10
Density of liquids with U-tube, balancing columns: 11.1.1
Electromagnetic conical pendulum: 29.2.6.12
Float an iron ball in mercury: 4.212
Interacting solenoids: 29.2.7.4
Maxwell's rule: 29.2.6.8
Mercury barometer, barometric pressure: 4.229
Mercury shaker: 31.1.21
Oscillating mercury, "chemical battery": 4.222
Parallel conductors: 29.2.6.1
Pinching mercury: 29.2.5.7
Pressure affects the boiling point: 2.8
Reaction time of equipment: 3.3.3.2, (mercury thermometer)
Simple barometer: 13.1.01
Thermometer test, calibrate a thermometer: 22.7.3
Ultraviolet light source: 4.136, (See 3.)

3.0.0 Mercury, Chemistry, Geology, Safety
Mercury, Hg, Table of elements
3.1.0 Mercury compounds
Mercury: 35.20.26, (Geology)
Mercury, Laboratory procedure: 7.2.2.28
Mercury metal
Activity series of metals as reducing agents: 12.14.0
Calomel, mercury (I) chloride: 35.20.10.1
Chemical spill kit, contains 2 kg sulfur, for mercury decontamination: 3.4.12
Chemicals not permitted in schools: 15.10.0
Chlorine dioxide, ClO2: 13.4.5
Cinnabar, HgS: 35.20.10.0, (Geology)
Daguerreotypes: 12.19.4.1
Group analysis, Explanation of group analysis: 17.5.7.0
Group 1 tests for Ag+, Pb2+, Hg+: 12.11.4.1
"Heat turned on medical equipment", (World Health Organization): 3.3.6
Merbromin
Mercury (I) chloride
Mercury (I) nitrate
Mercury (I) perchlorate tetrahydrate
Mercury (II) acetate, C4H6O4Hg, Hg(OAc)2
Mercury (II) chloride
Mercury (II) cyanide, gold mining contaminant
Mercury (II) iodide
Mercury (II) nitrate
Mercury (II) oxide
Mercury (II) sulfide
Mercury in barometers and thermometers: 1.9
Mercury compounds, Not permitted in schools: 3.1.0
Mercury fulminate
Mercury metal, redistilled, quicksilver, (alchemist: azoth): 7.0.6
Mercury properties: 7.2.2.27
Mercury residues: 3.4.12.4
Mercury toxicity: 3.6.10
"Mercury's silent toll on the world's wildlife": 3.3.5, (Biology)
Methyl mercury, CH3Hg+
Millon's reagent, Tests for proteins, Millon's test: 16.6.7
Nessler's reagent, K2HgI4
Odour and taste: 35.15
Old Nassau flag clock reaction: 17.1.7, (mercury (II) iodide)
Organomercury: methyl mercury CH3Hg+, ethyl mercury C2H5Hg+, dimethyl mercury (CH3)2Hg, merbromin C20H8Br2HgNa2O6
Poisons and First Aid: 3.10.0, (Millons's reagent, Mercury and mercury compounds, mercuric chloride)
Primary ore deposits: 35.3.01
Reactions of mercury compounds: 12.8.4
Separate metals by reduction of metal oxides, ores: 10.10.0, (Not mercury)
Sodium amalgam
Sushi warning: 3.3.5.1, (Cooking)
Tests for proteins, Millon's test: 16.6.7
Toxicity, Poisons and First Aid: 3.10.0
Toxicity: 3.6.01
Waste bottles: 7.9.55.1
Zenker's fluid, biology fixative, (mercuric chloride): 4.6

Mercury metal
Mercury is a heavy metal that is widespread and persistent in the environment.
It is a naturally occurring element and can be released into the air and water through weathering of rock containing mercury ore, or
through human activities such as industrial processes, mining, deforestation, waste incineration, and burning of fossil fuels.
Mercury can also be released from a number of mercury-containing products, including dental amalgam, electrical applications (e.g.
switches and fluorescent lamps), laboratory and medical instruments,   (e.g. clinical thermometers and barometers), batteries, seed
dressings, antiseptic and antibacterial creams, and skin-lightening creams.
Mercury exposure can affect foetal neurological development and has been linked to lowered fertility, brain and nerve damage, and
heart disease in adults who have high levels of mercury in their blood.
Since 2001, the UN Environment Programme Governing Council/Global Ministerial Environment Forum (UNEP GC/GMEF) regularly
discussed the need to protect human health and the environment from the releases of mercury and its compounds.
The sixth session of the Intergovernmental Negotiating Committee to Prepare a Global Legally Binding Instrument on Mercury (INC6)
convened from 3-7 November 2014, in Bangkok, Thailand. INC6 carried out work to prepare for the entry into force of the Minamata
Convention on Mercury and for the first meeting of the Conference of Parties (COP1).
Over 300 participants attended the session, representing 122 governments, as well as 29 non-governmental and 13 intergovernmental
organizations.
Following a round of regional group meetings on Sunday, 2 November, delegates began their work.
Issues under consideration included, inter alia: importing mercury, registering exemptions, reporting and monitoring, rules of procedure
and financial rules for the COP, guidance and assistance to countries with artisanal and small-scale gold mining, storage, wastes and
management of contaminated sites, and operation of the financial mechanism.

Merbromin
Merbromin, C20H8Br2HgNa2O6 + dark red fluorescein, 2% solution = Mercurochrome, " monkey blood", household topical
antiseptic when suspended in water or alcohol,  stains the skin red to brown, no longer sold in USA probably because it contains
mercury, despite no evidence that it is not safe for topical use.

Mercury (I) chloride
Calomel, horn quicksilver, Hg2Cl2: 35.20.10.1 (Mineral)
Calomel half cell, Hg2Cl2 : 15.6.16
Calomel, Standard electrode potential, E0: 3.84.6

Mercury (I) chloride, Hg2Cl2, calomel, mercurous chloride horn quicksilver, white crystals, r.d. 7.15, sublimes at 400oC, (reference
electrode in calomel electric cells, mercury electrode in potassium chloride solution + calomel).
Calomel is found with cinnabar mineral, is a former laxative, and has low toxicity
Formerly, calomel was a tasteless, grey, usually powdered, medicine used as a purgative.
Calomel is found with cinnabar mineral.
Formerly used as a laxative.
Solution / mixture < 25%, Not hazardous

Mercury (I) nitrate dihydrate (Millon's reagent)
Tests for proteins, Millon's test: 16.6.7
Millon's reagent contains mercury (I) nitrate, mercurous nitrate, in nitrous acid.
Mercury (I) nitrate dihydrate, Hg2(NO3)2.2H2O, mercurous nitrate dihydrate, forms explosive mixtures with combustible materials
and organic compounds.
Mercury (I) nitrate was formerly used in the manufacture of felt hats, and caused tremors in the workers and leading to the term "mad
as a hatter".
The "mad hatter" is a character in "Alice in Wonderland" by Lewis Carroll.
Low Toxicity if pure chemical ingested, explosive mixture with combustibles or organic compounds
Solution < 0.1%, Not hazardous but use < 5 mL of 0.1 M per activity
The pure chemical has low toxicity if ingested.
Mercury (I) nitrate is used in redox reactions and metal displacement reactions.

Mercury (II) chloride
Mercury (II) chloride, HgCl2, mercuric chloride, mercury bichloride, mercury sublimate, corrosive sublimate, mercury perchloride
Colourless, white crystalline solid, odourless, rhombic crystals, powder or granules, r.d. 5.4, m.p. 277oC,  solution is poisonous and
very dangerous because the solution looks like water.
Mercury (II) chloride should NOT be in the school laboratory!
It was formerly used to treat syphilis.
Used for manufacture of disinfectants, catalyst. photography, embalming.
Bacteria in the water and the soil primarily produce methyl mercury.
Mercuric chloride is soluble in water and  in most organic solvents, but methyl mercury is not soluble.
Contact with mercuric chloride can cause burns to the skin and permanent damage to the eyes.
Methyl mercury builds up in the tissues of fish and shellfish.
Photographic toners contain mercuric chloride
Mercuric chloride is slightly volatile at ordinary temperatures.
Melting Point: 277oC Boiling Point: 320oC Specific Gravity: 5.4 Vapour Pressure: 1.3 (mm Hg /21oC)
Mercury (II) chloride, HgCl2, Highly toxic if ingested or absorbed through skin
Mercury (II) chloride, vermilion, China red, opaque red pigment, from cinnabar mineral
Mercury (II) chloride, Solution < 0.1% Not hazardous but should not be ingested
Corrosive sublimate, HgCl2, mercury (II) chloride, mercuric chloride,
Highly toxic if ingested or absorbed through skin
Zenker's fluid, biology fixative, (mercuric chloride): 4.6

Mercury (II) fulminate
Mercury (II) fulminate, mercury fulminate, Hg(CNO)2.H2O, Hg(ONC)2, contact explosive, in detonators and percussion caps

Mercury (II) iodide
Mercury (II) iodide, HgI2, mercuric iodide, mercury iodide
Highly toxic if ingested or absorbed through skin
Solution < 0.1%, Not hazardous but should not be ingested
Nessler's reagent / solution (K2HgI4, HgI2 in KI), tests for ammonium radical, NH4+: 11.3.10.2
Old Nassau flag clock reaction, (orange and black) sodium metabisulfite, Mercury (II) iodide: 17.1.7

Mercury (II) nitrate
Mercury (II) nitrate monohydrate, Hg(NO3)2.H2O, mercuric nitrate monohydrate.
Highly toxic if ingested, cumulative poison, Highly toxic if ingested or absorbed through the skin, cumulative poison.
Use eye and skin protection when splashes can occur.
Forms explosive mixtures with combustible materials and organic compounds.
Do NOT heat the solid because mercury vapour and nitrogen dioxide forms.
Do NOT add ethanol to solutions of mercury (II) nitrate in nitric acid because highly explosive mercury fulminate forms.
Do NOT use for redox reactions.
Use < 5 mL of 0.1 M per activity.

Mercury (II) oxide
Mercuric oxide battery: 3.3.7
Mercury (II) oxide, HgO, red mercuric oxide,
Highly toxic if ingested, cumulative poison
Mercury (II) oxide, Solid mixture < 0.1%, Not hazardous
Mercury (II) oxide, HgO, mercuric oxide, "red calyx of mercury", yellow to orange, dense, odourless powder,
 r.d. 11.14, decomposed by light, yellow oxide of mercury or red oxide of mercury, store in dark bottles,
Do not heat to form oxygen gas because highly toxic mercury vapour forms.
Mixture with powdered sulfur is explosive.
Do NOT heat mercury (II) oxide to form oxygen gas, because highly toxic mercury vapour forms.
Mixture with powdered sulfur is explosive.

Mercury (II) sulfide
Mercury (II) sulfide, HgS, cinnabar, metacinnabar, mercury (II) sulfide red: 35.20.10.0
Mercury (II) sulfide pigment, (vermilion, cadmium vermilion red, red 106, Chinese red), highly toxic, cumulative poison

1.9 Mercury in barometers and thermometers
1. Thermometers supplied to schools usually contain alcohol and not mercury.
Avoid leaving thermometers in containers where they are easily knocked over by students.
To monitor the temperature continuously, clamp the thermometer in position.
If recording the temperature at regular intervals, return the thermometer to its container between measurements.
Do not leave thermometers on the desk where they may be moved by the elbows or the back of the hand.
Do not place laboratory thermometers in the mouths of students.
Do not use thermometers to stir liquids because the liquid in the thermometer may separate, making it unusable.
However, you can put the thermometer in a refrigerator freezer until the liquid recombines.
Do not try to recombine the liquid by heating the thermometer because it may explode.
Senior secondary classes may use barometers and thermometers containing mercury, but primary and junior secondary classes should
use alcohol thermometers and they may observe a mercury barometer attached to the wall, if supplied by the education authority.

2. Do not use mercury in school experiments.
However, students may observe some properties of mercury by studying it as enclosed in a barometer or thermometer supplied by the
education authority.
Do not make a barometer or a thermometer using mercury.
Mercury vapour is TOXIC and may damage the nervous system.
Mercury enters the body readily by inhalation by ingestion or through the skin.
If mercury is spilt from a broken thermometer, immediately pick up all the mercury with pieces of stiff cardboard, e.g. a bent playing
card, or with a damp cloth or a water suction pump.
Do not use a vacuum cleaner or a broom.
Do not put spilt mercury down the drain.
Sprinkle sulfur powder or zinc powder over the area of the spillage and collect it with a moist absorbent paper.
Shine a light on the spillage to see the mercury globules.
Report any mercury spill to the school authorities.
Give any spilt mercury or mercury stored in the school laboratory to a government laboratory.

4. The World health Organization, working with the UN agency Health Care Without Harm, has launched a campaign to eliminate
mercury from fever thermometers and blood pressure devices by 2020.

3.0.0 Mercury and dental amalgam
Statement approved by the 107th session of the National Health and Medical Research Council, Sydney, Australia.
"An amalgam is a metal alloy where one component is mercury.
Dental amalgam is prepared by mixing silver-tin powder with liquid mercury.
The resulting mix then hardens to form a stable solid as mercury forms compounds with the silver and tin.
Dental amalgam is an excellent material for repairing decayed teeth, and for many applications it is still preferable to the alternatives.
Amalgam is stronger, and therefore lasts longer than the composite resins (plastics) or synthetic cements.
Amalgam is chemically much less damaging to the local tissues than these materials, and it keeps bacteria out extremely well.
As some forms of mercury are toxic, the safety of dental amalgam for dental patients, and for dental care workers, has been thoroughly
examined.
The vapour of pure mercury does pose a health hazard if it is inhaled either in very high concentrations for a short time or in moderate
concentration for months or years.
Mercury vapour crosses the lungs into the blood quite readily, and then moves from the blood into other tissues.
This is a possible risk to dental health workers if mercury hygiene is not practised and their workplace becomes contaminated, but it is
not a risk to patients receiving amalgam fillings because their exposure to vapour is extremely low.
Also, the occasional inorganic mercury compounds, such as those formed when dental amalgam is mixed, are poorly absorbed and are
readily excreted by the kidneys.
Mercury compounds are present in many foods in low concentrations and cause no harm.
The health and well being of dental patients who have received amalgam fillings has been studied thoroughly, and the following findings
 were arrived at:
1. There is no difference in the incidence of any disease or in the length of life between people who have amalgam fillings and those who
do not.
2. People who have amalgam fillings and then have them removed do not experience an improvement in health.
3. People who have no teeth, and therefore no amalgam fillings, are not healthier than people with amalgam-filled teeth.
4. Rarely, allergy to amalgam occurs as a local rash on the cheek or tongue next to a filling.
For patients with such allergy, material other than amalgam should be used.
Dentists and dental researchers are interested in finding ways to repair teeth without using dental amalgam, because of the industrial risks
that amalgam poses to dental care personnel.
Patients sometimes request fillings made with materials other than amalgam, because of the concerns about safety and appearance.
Some alternative materials can be used, but they are often less satisfactory than amalgam from the point of the patient's long term health
and well being.
Dental amalgam is still the material of choice for the repair for most medium sized areas of tooth decay in premolar and molar teeth.
The objective of the National Health and Medical Research Council is to advise the Australian community on the achievement and
maintenance of the highest practicable standards of the individual and public health and to foster research in the interest of improving
those standards."
[Editorial comment: The research is not very clear and confusing.
Properly and accurately mixed amalgams are probably sufficiently stable to not cause any problems over a lifetime.
Inaccurately mixed amalgams may leak (leach) enough mercury to cause some minor effects after a long time in a small number of
genetically pre-disposed individuals.
Another issue for the dental professions was what else to use?
It has only been in the past few years that useful alternatives have been available.
About half the current dentists use the alternatives.
Previously, students studied the interesting chemistry of mercury salts.
To my knowledge, there has not been one health problem related to mercury in these thousands of students.]

Methyl mercury, CH3Hg+
Methyl mercury is soluble in most organic solvents.
Mercury released into the environment is converted into methyl mercury by bacteria.
The methyl mercury will then build up in the tissues of fish and shellfish.
Humans (and other animals) may also be poisoned by eating these fish or shellfish.

7.2.2.27 Mercury properties
See: Mercury (Commercial)
Warning
Mercury is not permitted in schools except in some school systems where it is allowed only in barometers and thermometers.
Mercury thermometers should only be used by senior students.
Junior students should use alcohol or electronic thermometers.
Avoid the use of mercury by using solid state electronic devices for measuring pressure
or use less dense liquids, even water, in a manometer, to demonstrate changes in pressure.

Mercury, Hg, (Latin Mercurius Roman god), Mercury (RD 13.60), (Latin hydrargyrum, formerly "quicksilver", Hg) is a liquid metal
between 19oC and 27oC, it has the lowest melting point of all substances, mp = -38.9oC, it is slightly volatile at ordinary temperatures.
Atomic number: 80, Relative atomic mass: 200.59, r.d.
13.6, mp: -38.9oC, bp: 357oC, Specific heat capacity: 138 J kg-1 K-1,  type 1 superconductor at 4.2 K, melting point 234.28 K
Density 13.60 g cm-3, Specific Gravity: 13.6 Vapour Pressure: 0.0012 (mm Hg / 21oC)
Anomalies in the properties of an element, e.g. mercury, Hg, is liquid at room temperature.

7.2.2.28 Mercury, Laboratory procedure
Mercury can evaporate even at 0oC.
Mercury vapour absorbed by the body is not detoxified by the body and may accumulate and cause complications with the nervous
system.
When mercury contacts with your skin you must thoroughly wash the area with soap and water immediately.
Mercury should be stored in an impervious container made of glass or china in a cool ventilated place.
While storing mercury under water is useful, it is not sufficient.
Mercury should be stored in a sealed container.
The container should be placed in a sealed cupboard or a sealed larger container or box.
There should be some powdered sulfur or powdered zinc alongside the mercury container to be used in case of emergency with a
mercury spill.
The table used for a mercury experiment should be smooth and no slits.
If there are some slits on the table make them smooth and cover it with paint.
Use mercury in a well-ventilated area that does not have porous surfaces.
Do not heat mercury because more toxic mercury vapour is given off.
Liquid mercury boils violently at atmospheric pressure.
Do not react mercury with chlorine or bromine because highly toxic salts are formed.
Mercury reacts with the gold in gold rings to form an amalgam and spoil the ring.

Spillage and cleanup
Mercury metal gives off a highly toxic vapour that acts as a cumulative poison.
Spilt mercury shatters into many tiny droplets that lodge in cracks in the floor and around skirting boards.
The droplets have a large total surface area and the mercury can evaporate slowly, over months or years causing long-term exposure
to low levels of mercury vapour in the air.
Any person working in the area may regularly inhale the mercury vapour, with adverse effects.
So spilt mercury must be immediately treated with sulfur powder or mercury decontaminant, a mixture of calcium hydroxide and sulfur,
to form low vapour pressure mercury (II) sulfide  that is stable and harmless and can be easily cleaned up from the polluted region.
Then sweep up the mercury and sulfur together.
If mercury is found to be leaking or spilt in a room, the persons in the room must go out of the room,  and open all the system of
ventilation and shut the doors next to that room.
Mercury that has leaked out should be absorbed by water pump or cleaned by wet cleaning agent.
Put the collected mercury into a glass bottle.
The person who cleans the mercury up should check that all the mercury has been cleaned up, and that none remains on the cleaning
cloth.
Always keep available 2 kg of sulfur or 2 kg of mercury decontaminant in the laboratory,  near any equipment containing mercury.
Liquid mercury is extremely dense, so the weight of even a small container may surprise some students who may then drop it.
If the pressure measured with a mercury-in-glass manometer, suddenly changes because of the careless opening of a tap, the moving
column of mercury may break the walls of the manometer and mercury spills out.
Do not place mercury thermometers in a dish washer for cleaning.
Drains in laboratories often contain significant amounts of mercury in the S-bends.
Periodically check the waste water filter of a laboratory dishwasher for liquid mercury.
Store mercury in a sealed container on a plastic tray to catch any spilt mercury.
Before disposal of broken thermometer debris or mercury-contaminated rubbish from S-bends, mix them with an equal volume of sulfur
powder.
Fit a tray containing a centimetre of sulfur powder beneath the apparatus, because mercury spilled on sulfur powder will not shatter into
fine droplets and the sulfur will inactivate the mercury.
Pour mercury over a plastic tray containing water so that any spilled mercury will not shatter into droplets, but form a lower layer that
can be recovered easily.
Uses for dentistry amalgams, mercury cathode in mercury cell, mercury solvent of metals to form amalgams, mercury vapour lamps,
electrical switches, interferometer lights, batteries, thermometers, barometers, thermostats and detonators, e.g. mercury fulminate.
Mercury is used in its pure form in thermometers and barometers and as a catalyst in the chemical industry.
It is also used in the mining industry to extract gold and silver ores.
Fluorescent lamps containing mercury vapour or neon gas are much more energy-efficient than incandescent lamps.

3.3.5 Mercury's silent toll on the world's wildlife
By Rebecca Kessler, Monday, 25 February 2013
This article was first published on Yale Environment 360.
Rebecca Kessler is a freelance science and environmental journalist based in Providence, Rhode Island.
This work is licensed under a Creative Commons License.
ON LINE opinion, Australia's e-journal of social and political debate

This month, delegates from over 140 countries gathered in Geneva and finalized the first international treaty to reduce emissions of
mercury.
The treaty - four years in the works and scheduled for signing in October - aims to protect human health from this very serious
neurotoxin.
But barely considered during the long deliberations, according to those involved in the treaty process, was the harm that mercury
inflicts on wildlife.
While mercury doesn't kill many animals outright, it can put a deep dent in reproduction, says David Evers, chief scientist at the
Biodiversity Research Institute (BRI), who serves on a scientific committee informing the process.
"It is a bit of a silent threat, where you have to kind of add up what was lost through studies and demographic models."
Harmful levels of mercury have turned up in all sorts of animals, from fish and birds living around the world to pythons invading the
Florida Everglades and polar bears roaming far from any sources of pollution.
In recent years, biologists have been tracking mercury's footprints in unexpected habitats and species.
Their research is illuminating the subtle effects of chronic exposure and is showing that ever lower levels cause harm.
Coal burning, gold mining, and other human activities release mercury into water bodies or the atmosphere, where it can travel great
distances before settling back to Earth.
Mercury contamination is ubiquitous and hot spots are common around the world, with fish and human hair collected in 14 countries
regularly exceeding U.S.
Environmental Protection Agency (EPA) standards, according to a BRI report released just before the Geneva negotiations.
And while mercury emissions are declining in North America and Europe, they are rising quickly in the developing world, according to
the United Nations Environment Programme, the treaty co-ordinator.
The new global treaty bans the production, import, and export of certain mercury-containing products, requires governments to create
plans to reduce mercury in small gold mining operations, and puts some controls on industrial facilities - but some environmental groups
warn that it is too weak.
The U.S. is going further.
On January 1, an export ban on elemental mercury took effect, and the EPA is finalizing new limits on coal plant emissions.
"In the end the treaty will reduce mercury that's being released into the environment.
And I think the question will be, as we move along,
"Is it enough?" - especially for areas that are sensitive to mercury input.
And then "Is it enough for wildlife conservation purposes?", which really wasn't addressed all that well, " Evers says.
Exposed animals have trouble ridding their bodies of mercury, and it accumulates in tissue with every link in the food chain.
Long-lived predators tend to carry the heaviest loads.
Research and public attention have largely focused on contaminated fish, the main route of human exposure.
In water, mercury converts quickly to methyl mercury, its most toxic and form, so for many years wildlife biologists
trained their sights on aquatic, fish-eating birds and mammals, says Bill Hopkins, a Virginia Tech physiological ecologist.
Lately, though, Hopkins and others have uncovered mercury in reptiles, amphibians, insects, spiders, terrestrial songbirds, and a wider
variety of mammals than expected.
"All these different groups can be exposed to mercury and pass it on to their babies, " says Hopkins.
Mercury is also turning up in strange places, he says.
Invertebrate-eating songbirds living in the flood plain bordering a contaminated Virginia river had as much mercury in their blood as the
river's fish-eating birds, and sometimes more, showing that mercury pollution doesn't stay put in aquatic habitats.
Scientists have found mercury-laden food chains in mountainous forests, and shown that methyl mercury forms in the woods, as well as
in water.
BRI scientists and collaborators discovered high levels in many invertebrate-eating songbird and bat species living in varied habitats
across the U.S. Northeast and Mid Atlantic states, including remote uplands.
The pollutant has also emerged as a serious problem in the Arctic.
Mercury plays havoc on vertebrates' development and their neurological and hormonal systems, and doses too low to kill can cause
problems that aren't always obvious in the wild, experts say.
"Methyl mercury is one of most toxic environmental pollutants we've ever come upon, " says Gary Heinz, a recently retired federal
wildlife biologist who studied it over four decades.
In the earliest studies of these sub lethal effects in the 1970s, Heinz reported that captive mallards fed mercury-laced food laid fewer
eggs than control ducks and laid them outside the nest.
Also, their ducklings didn't respond well to their calls.
Numerous examples have accumulated since.
Fish form loose, sloppy schools and are slow to respond to a simulated predator.
Several bird species sing different songs.
Loons lay smaller eggs, and they incubate their nests, forage, and feed their chicks less.
Salamanders are sluggish and less responsive to prey, Hopkins and colleagues found.
Egret chicks are similarly lethargic and unmotivated to hunt.
Changes like these could be grave for wild animals, says Peter Frederick, a University of Florida ecologist who was part of the egret
study.
"Getting lunch or a mate depends on milliseconds and millimetres.
They have to do that courtship dance just right.
You have to make the calls just right.
You have to stab your prey to within a millimetre.
If you're off by a microsecond, it's gone, " he says.
Frederick discovered a remarkable example in white ibises from the Everglades.
There, mercury levels are low but constant, and ibises seem to nest less and abandon their nests more often than elsewhere.
To see if chronic mercury exposure was responsible, Frederick captured 160 ibis nestlings and fed them food with mercury levels
similar to their wild fish prey.
He and his team observed the birds for three years to see if it affected their breeding behaviour.
As expected, the dosed birds produced far fewer offspring than undosed controls.
There were the usual reasons: eggs didn't hatch and chicks died under lousy parenting.
But Frederick was wholly surprised to see widespread homosexual pairing among the dosed males and to find this caused much of the
reproductive deficit.
"Avian homosexuality usually occurs with stark sex imbalances, which wasn't the case here", Frederick says.
"No one had ever reported homosexuality as an effect of mercury, or any other contaminant for that matter", Frederick says.
Moreover, the effects appeared in ibises he'd fed as little as 0.05 ppm of mercury in their food, one tenth of what Heinz fed his mallards.
Further work indicated that hormonal changes wrought by mercury's effects on the ibises' endocrine systems were at work.
In a 2011 paper, Frederick and a colleague estimated that out in the Everglades, mercury could cut the number of ibis fledglings by half
- easily enough to curtail the population.
"No one has checked wild ibises for poor parental behaviour or homosexuality, which might lay the blame more squarely on mercury",
he says.
(Different species react to mercury differently, and Frederick stresses that for many reasons his results in no way suggest that mercury
might play a role in human homosexuality.)
Nevertheless, the broader implications for chronically exposed wildlife are chilling.
"We can be essentially neutering populations by cutting off reproduction through the endocrine system, " he says.
"This could easily be going on in the wild with many kinds of contaminants.
Mercury is not the only endocrine disrupter."
Like Frederick's study, much of the research on mercury's sub lethal effects has been conducted on captive animals.
In nature, it's very difficult to get the large sample sizes and control groups needed to identify subtle differences statistically, says Erick
Greene, a conservation biologist at the University of Montana.
Studying ospreys living near Montana's polluted Clark Fork River, Greene and two colleagues found that about half the eggs laid by
high mercury birds fail to hatch.
But they've been puzzled as to whether the surviving chicks are affected.
"In humans, blood levels around .005 ppm can cause cognitive deficits", Greene says.
But his osprey chicks commonly have levels 100 - and even 1, 000 - times higher.
The chicks seem to do fine in the nest, he says.
"They may look all right, but I don't know if I would recognize a mentally impaired osprey chick."
Once they're fledged they soon migrate south, out of sight.
Greene suspects they may have trouble making the demanding migration to Central or South America  (where mercury flows freely in
small gold mining operations), or just figuring out how to survive on their own.
His team has begun outfitting fledglings with satellite transmitters to determine how far mercury-loaded birds get compared to their
normal peers, and how long they live.
It's one thing to show that wild animals are exposed to harmful levels of mercury, but solid evidence that whole populations are harmed
is harder to come by, experts say.
A notable exception is loons.
Evers and more than a dozen colleagues amassed an impressive 18-year data set of nearly 5, 500 mercury measurements from loons
on 700 lakes across 17 U.S. states and Canadian provinces.
They showed that when mercury in loon blood hits 3 ppm, the number of young fledged drops by 41 percent, and that enough loons
are affected to set back some New Hampshire and Maine populations.
In a forthcoming paper, Hopkins and another researcher go a step further with a population model they developed based on four years
of field data on American toads.
Toads readily move between small populations scattered throughout the landscape.
Mercury exposure can kill eggs and tadpoles, and survivors are often small and slow to mature.
The model revealed that not only can mercury kill enough tadpoles to wipe out small populations, but that nearby uncontaminated
populations can also drop or go extinct, because there are too few toads around to replenish them if their numbers happen to dip fo
 other reasons.
Hopkins says he thinks the paper will change biologists' understanding of contaminants.
"Contaminant effects in one population can actually affect adjacent populations that aren't being exposed to that contaminant, " he says.
Whatever its weaknesses, the new treaty represents a "great step forward, " says Evers, and the good news is that once local sources
are controlled, mercury in nearby wildlife can drop quickly.
The bad news is that mercury from coal burning can travel great distances, for instance, from China to North America - before settling.
Overall, Evers says the forecast for wildlife is cloudy.
When it comes to mercury, "the more we look the more we find, and the more we find the lower that toxicity level is going, " he says.
"Right now at a global level, mercury is just being released more and more in the system.
Those trend lines are going in the wrong directions."

3.3.5.1 Warning on sushi
Bigger fish eat smaller fish, so the larger the fish, the greater the possible concentration of methyl mercury.
Researchers from Rutgers University, near new York, found that eating a lot of sushi increases the risk of exposure to dangerous levels
of mercury.
The researchers say the fish contains methyl mercury which can cause heart disease, problems with brain and nervous system
development and decreased cognitive performance.
Large tuna, e.g. atlantic blue fin, had the highest level of methyl mercury, but also eel, crab, salmon and kelp contain it.

3.3.6 "Heat turned on medical equipment", (World Health Organization)
Courier Mail (Brisbane) October 12, 2013
The World Health Organization and anti-mercury campaigners have launched a drive to wipe out the heavy metal in medical
thermometers.
The move came a day after representatives of 140 nations signed an UN treaty to control the use of mercury.
"Mercury is one of the top l0 chemicals of major public health concern and is a substance that disperses into and remains in ecosystems
for generations, causing severe ill health and intellectual impairment to exposed populations, " WHO director-general Margaret Chan said.
Working with the campaign group Health Care Without Harm, the UN agency said it aimed by 2020 to eliminate mercury from fever
thermometers, and blood pressure devices that use it.
The goal would be achieved if the manufacture, import and export of such devices were halted and accurate,  affordable, and safer
non-mercury alternatives were deployed.
In Japan, delegates from more than 140 countries and territories signed an UN treaty on mercury, in the city of Minamata.
The location was highly symbolic, as Minamata was the scene of a mercury scandal exposed in the 195Os.

3.3.7 Mercuric oxide battery
Mercuric oxide button-cell batteries, similar to silver oxide batteries, were banned in 1996 in accordance with the "Mercury Containing
and Rechargeable Battery Management Act", and are no longer sold in the U.S.A.
Larger mercuric oxide batteries may still be used in industrial equipment.
Before this batteries were banned, the sludge contents of a run down battery could be distilled to retrieve the mercury.
Cathode: (mercuric oxide or mercuric oxide + manganese dioxide) + graphite to prevent large droplets of mercury pooling.
Anode: zinc
Separation: paper or porous material soaked with electrolyte.
Discharge reaction: zinc oxidizes to zinc oxide, mercuric oxide reduced to elemental mercury.
Extra mercuric oxide prevents formation of hydrogen gas when battery run down.
mercuric oxide --> mercury metal
HgO + H2O + 2e- --> Hg + 2OH-
zinc --> zinc oxide
Zn + 2OH- --> ZnO + H2O + 2e-
potassium hydroxide electrolyte
KOH <--> K+ + OH-
Cell reaction
Zn + HgO --> ZnO + Hg

12.8.4 Reactions of mercury compounds
Mercury metal and mercury compounds are not used in school science experiments.
Mercury forms mercury (I) and mercury (II) salts.
Mercury is very low in the electrochemical series and so nearly all metals precipitate it from solution.
Mercury hydroxide, carbonate and oxide are unstable and produce mercury when heated.
Mercury (I) salts in solution form the unusual ion Hg22+.
However, mercury (II) salts ionize only slightly.
Mercury, a naturally occurring element that rarely occurs free in rock cavities, is an odourless, very heavy, silver white, liquid metal.
Pure mercury is stable and does not tarnish at ordinary temperatures.
It will form alloys with most metals.
It is not soluble in water or most other liquids, but will dissolve in lipids (fats and oils).
It is an excellent conductor of electricity.
Mercury dissolves in most metals to produce amalgams.
It reacts with concentrated oxidizing acids, HNO3 or H2SO4 to produce high oxidation number ions, and sulfur dioxide SO2 or nitrogen
dioxide, NO2.
No reaction with dilute HCl or H2SO4 or with water.
Heated powder forms oxide.
It is extracted from cinnabar (mercury (II) sulfide).
Sodium amalgam, NaHg2, is formed by electrolysis of sodium chloride solution with a mercury cathode.
Mercury and mercury salts react with aluminium in a violently exothermic reaction.