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Application Of Hg in Bio-inorganic Chemistry

Mercury Mercury is a chemical element with the symbol Hg and atomic number 80.Mercury was used for preserving wood, developing daguerreotypes, silvering mirrors, anti-fouling paints (discontinued in 1990), herbicides (discontinued in 1995), handheld maze games, cleaning,and road leveling devices in cars.It was allegedly used by allied spies to sabotage Luftwaffe planes: a mercury paste was applied to bare aluminium, causing the metal to rapidly corrode; this would cause structural failures.As electrodes in some types of electrolysis, batteries (mercury cells), sodium hydroxide and chlorine production, handheld games, catalysts, insecticides.Mercury was once used as a gun barrel bore cleaner.Chloralkali process: The largest industrial use of mercury during the 20th century was in electrolysis for separating chlorine and sodium from brine; mercury being the anode of the Castner-Kellner process.From the mid-18th to the mid-19th centuries, a process called "carroting" was used in the making of felt hats. Animal skins were rinsed in an orange solution (the term "carroting" arose from thiscolor) of the mercury compound mercuric nitrate, Hg(NO3)2o2H2O.The psychological symptoms associated with mercury poisoning inspired the phrase"mad as a hatter". Lewis Carroll's "Mad Hatter" in his book Alice's Adventures in Wonderland was a play on words based on the older phrase, but the character himself does not exhibit symptoms of mercury poisoning.Historically, mercury was used extensively in hydraulic gold mining in order to help the gold to sink through the flowing water-gravel mixture.Gold and silver mining.

Application Of Hg in Bio-inorganic Chemistry

Mercury
Mercury is a chemical element with the symbol Hg and atomic number 80.

It is commonly known as quicksilver and was formerly named hydrargyrum (from Greek "hydr-" water and "argyros" silver .

A heavy, silvery d-block element, mercury is the only metallic element that is liquid at standard conditions for temperature and pressure; the only other element that is liquid under these conditions is bromine, though metals such as caesium, gallium, and rubidiummelt just above room temperature.Mercury occurs in deposits throughout the world mostly as cinnabar (mercuric sulfide).

The red pigment vermilion, a pure form of mercuric sulfide, is mostlyobtained by reaction of mercury (produced by reduction from cinnabar) with sulfur.

Cinnabar is highly toxic by ingestion or inhalation of the dust. Mercurypoisoning can also result from exposure to water-soluble forms of mercury (such as mercuric chloride or methylmercury), inhalation of mercury vapor, or eating seafood contaminated with mercury.

Mercury is used in thermometers,barometers,manometers,sphygmomanometes, float valves, mercury switches, mercury relays, fluorescent lamps andother devices though concerns about the element's toxicity have led to mercury thermometers and sphygmomanometers being largely phased out in clinicalenvironments in favour of alternatives such as alcohol or galinstan-filled glass thermometers, thermistor or infrared-based electronic instruments.

Likewisemechanical pressure gauges and electronic strain gauge sensors have replaced mercury sphygmomanometers.

It remains in use in scientific researchapplications and in amalgam material for dental restoration in some locales. It is used in lighting: electricity passed through mercury vapor in a fluorescentlamp produces short-wave ultraviolet light which then causes the phosphor in the tube to fluoresce, making visible light.

Applications
Mercury is used primarily for the manufacture of industrial chemicals or for electrical and electronic applications.
It is used in some thermometers, especially ones whichare used to measure high temperatures.

A still increasing amount is used as gaseous mercury in fluorescent lamps, while most of the other applications are slowlyphased out due to health and safety regulations and is in some applications replaced with less toxic but considerably more expensive Galinstan alloy.

MedicineSee also: Amalgam (dentistry)

Mercury and its compounds have been used in medicine, although they are much less common today than they once were, now that the toxic effects of mercury and itscompounds are more widely understood.

The first edition of the Merck's Manual featured many mercuric compounds [41]
suchas:MercauroMercuro-iodo-hemol.

Mercury-ammonium chlorideMercury BenzoateMercuricMercury Bichloride (Corrosive Mercuric Chloride, U.S.P.)Mercury ChlorideMild Mercury CyanideMercury SuccinimideMercury IodideRed Mercury BiniodideMercury IodideYellow Mercury Proto-iodideBlack (Hahnemann), Soluble Mercury OxideRed Mercury OxideYellow Mercury OxideMercury SalicylateMercury SuccinimideMercury Imido-succinateMercury SulphateBasic Mercury Subsulphate; Turpeth MineralMercury Tannate Mercury-Ammonium ChlorideThe element mercury is an ingredient in dental amalgams.

Thiomersal (called Thimerosal in the United States) is an organic compound used as a preservative in vaccines, though this use is indecline.

Thiomersal is metabolized to ethyl mercury. Although it was widely speculated that this mercury-based preservative could cause or trigger autism in children, scientific studies showed noevidence supporting any such link.

Nevertheless thiomersal has been removed from or reduced to trace amounts in all U.S. vaccines recommended for children 6 years of age and under, with theexception of inactivated influenza vaccine.

Another mercury compound merbromin (Mercurochrome) is a topical antiseptic used for minor cuts and scrapes is still in use in some countries.
Mercury in the form of one of its common ores, cinnabar, is used in various traditional medicines, especially in traditional Chinese medicine.

Review of its safety has found cinnabar can lead to significantmercury intoxication when heated, consumed in overdose or taken long term, and can have adverse effects at therapeutic doses, though this is typically reversible at therapeutic doses.

Although thisform of mercury appears less toxic than others, its use in traditional Chinese medicine has not yet been justified as the therapeutic basis for the use of cinnabar is not clear.

Today, the use of mercury in medicine has greatly declined in all respects, especially in developed countries. Thermometers and sphygmomanometers containing mercury were invented in the early 18thand late 19th centuries, respectively. In the early 21st century, their use is declining and has been banned in some countries, states and medical institutions. In 2002, the U.S. Senate passed legislationto phase out the sale of non-prescription mercury thermometers.

In 2003, Washington and Maine became the first states to ban mercury blood pressure devices.

Mercury compounds are found insome over-the-counter drugs, including topical antiseptics, stimulant laxatives, diaper-rash ointment, eye drops, and nasal sprays. The FDA has "inadequate data to establish general recognition of the safety and effectiveness", of the mercury ingredients in these products.

Mercury is still used in some diuretics, although substitutes now exist for most therapeutic uses.

Others applications made use of the chemical properties of mercury:The mercury battery is a non-rechargeable electrochemical battery, a primary cell, that was common throughout the middle of the 20th century.
It was used in awide variety of applications and was available in various sizes, particularly button sizes.
Its constant voltage output and long shelf life gave it a niche use for camera light meters and hearing aids. The mercury cell was effectively banned in most countries in the 1990s due to concerns about the mercury contaminatinglandfills.
Mercury was used for preserving wood, developing daguerreotypes, silvering mirrors, anti-fouling paints (discontinued in 1990), herbicides (discontinued in 1995), handheld maze games, cleaning,and road leveling devices in cars. Mercury compounds have been used in antiseptics, laxatives, antidepressants, and in antisyphilitics.
It was allegedly used by allied spies to sabotage Luftwaffe planes: a mercury paste was applied to bare aluminium, causing the metal to rapidly corrode; this would cause structural failures.
Chloralkali process: The largest industrial use of mercury during the 20th century was in electrolysis for separating chlorine and sodium from brine; mercury being the anode of the Castner-Kellner process.
The chlorine was used for bleaching paper (hence the location of many of these plants near paper mills) while the sodium was used to make sodium hydroxide for soaps and other cleaning products. This usage has largely been discontinued, replaced with other technologies that utilize membrane cells.
As electrodes in some types of electrolysis, batteries (mercury cells), sodium hydroxide and chlorine production, handheld games, catalysts, insecticides.Mercury was once used as a gun barrel bore cleaner.
From the mid-18th to the mid-19th centuries, a process called "carroting" was used in the making of felt hats. Animal skins were rinsed in an orange solution (the term "carroting" arose from thiscolor) of the mercury compound mercuric nitrate, Hg(NO3)2•2H2O.
This process separated the fur from the pelt and matted it together. This solution and the vapors it produced were highly toxic.
The United States Public Health Service banned the use of mercury in the felt industry in December 1941.
The psychological symptoms associated with mercury poisoning inspired the phrase"mad as a hatter".
Lewis Carroll's "Mad Hatter" in his book Alice's Adventures in Wonderland
was a play on words based on the older phrase, but the character himself does not exhibit symptoms of mercury poisoning.
Gold and silver mining. Historically, mercury was used extensively in hydraulic gold mining in order to help the gold to sink through the flowing water-gravel mixture.
Thin gold particles may formmercury-gold amalgam and therefore increase the gold recovery rates.
Large-scale use of mercury stopped in the 1960s. However, mercury is still used in small scale, often clandestine, goldprospecting.
It is estimated that 45,000 metric tons of mercury used in California for placer mining have not been recovered.

Bio-inorganic Chemistry
Bioinorganic Chemistry is devoted to all aspects of “inorganic elements” (such as
Transition metals) as being vital for the growth and metabolism of living systems.
Bioinorganic Chemistry is a multidisciplinary field which draws on expertise in
Biochemistry, chemistry, crystallography, genetics, medicine, microbiology together with
The effective application of advanced physical methods.
Organic chemistry at one time was thought to be the chemistry involved in living systems
Because compounds of carbon were found to be playing the key role in all biological
Processes. However slowly it was realized that metal ions play a vital role in a vast number
Of widely differing biological processes. Some of these processes are quite specific in their
Metal ion requirements in that only certain metal ions, in specified oxidation states can
Fulfill the necessary catalytic or structural requirements. A large number of metal ions are
Involved in biological processes. This can be verified by just going through the protein data
Banks e.g. in Brookhaven Protein Data Bank 52% proteins contain metals (excluding
Weakly bound metals such as sodium). This count includes proteins and enzymes with heme
And coring groups and mutated forms of certain metallobiomolecules and structures of the
Same enzyme with different substrates and inhibitors. Metal ions play essential roles in
About one third of enzymes. These metal ions can modify electron flow in a substrate or
Enzyme, thus effectively controlling an enzyme-catalyzed reaction. They can serve to bind
And orient substrate with respect to functional groups in the active site, and they can provide
A site for redox activity if the metal has several valence states. Without the appropriate
Metal ion, a biochemical reaction catalyzed by a particular metalloenzyme would proceed
Very slowly, if at all. So bio-inorganic chemistry comes in to the play. Bioinorganic
Chemistry encompasses a variety of disciplines, ranging from inorganic chemistry and
Biochemistry to spectroscopy, molecular biology, and medicine etc. The field is undergoing
A phase of explosive growth, partly because of exposure and insights obtained by large
Number of x-ray structures of several metalloenzymes.

Uses of Mercury
Mercury metal have many applications. Because of its high-density, mercury is used in thermometers, barometers, manometers, sphygmomanometers, float valves, mercury switches, mercury relays, fluorescent lamps and other devices.
The mercury compounds have many uses:
• The Calomel – mercurous chloride ( Hg2Cl2) is used as a standard in electrochemical measurements and in medicine as a purgative.
• The mercuric chloride – corrosive sublimate ( HgCl2 ) is used as an insecticide such as rat poison and disinfectant.
• Mercuric oxide is used in skin ointments.
• Mercuric sulphate is used as a catalyst in organic chemistry.
Mercury is used in barometers, manometers, thermometers, sphygmomanometers, mercury switches, float valves, mercury relays, fluorescent lamps and other instruments. At the same time, concerns about the toxicity of the element have led to mercury thermometers and sphygmomanometers being increasingly phased out in clinical settings in favour of alternatives such as glass thermometers and thermometers filled with alcohol or galinstan Similarly, mercury sphygmomanometers have replaced mechanical pressure gauges and electronic strain gauge sensors.
Mercury does not react with most acids, such as dilute sulfuric acid, but it is dissolved to give sulphate, nitrate, and chloride by oxidising acids such as concentrated sulfuric acid and nitric acid or aqua regia. Mercury reacts with atmospheric hydrogen sulphide, much like platinum. Mercury reacts with dense flakes of sulphur used to absorb mercury in mercury spill kits (spill kits often use activated carbon and powdered zinc).
Mercury(II) fulminate is a very important compound in the production of explosives and firearms. This compound is commonly used in weapons as a primer of the cartridge. Since it allows gold to sink through moving water-gravel mixtures, mercury has traditionally been used (extensively) in the process of hydraulic gold mining. Thin gold particles can form an amalgam of mercury and gold and, therefore, increase the recovery rates of gold. In the 1960s, large-scale mercury use ceased (due to its toxicity). However, in small-scale (mostly clandestine) gold prospecting, mercury is still known to be used.
In some places, amalgam is still used for dental repair, and there are still some food manufacturing processes that use mercury and its derivatives. In the production of food, mercuric chloride is used to suppress enzymes that break down starch during the starch extraction process in the refining of rice, maize and wheat. Additionally, fluorescent lighting uses it. Short-wave ultraviolet light is created when electricity is delivered through mercury vapour in a fluorescent lamp. This light then causes the phosphor in the tube to glow, producing visible light.

APPLICATIONS OF MERCURY
Mainly, mercury as an element is popularly known to be in thermometers. It is also used in other types of scientific apparatuses, such as vacuum pumps, barometers, and electric rectifiers and switches. Mercury-vapor lamps are used as a source of ultraviolet light and for sterilizing water.
Because of the extremely toxic effects of mercury, the use of the metal and its compounds has been reduced in several industries, including pharmaceuticals, dentistry, and agriculture.
Even though some don't use mercury, mercury still is present because of its properties that make it fit to its applications. So, here are some applications mercury may be applied... and why does mercury used in this application. I have choose three applications of mercury to be discussed in this paper: the thermometer, the barometer and the.
II. Mercury in Thermometers
Mercury is used as the temperature medium material in a thermometer.
Mercury tends to make a temperature reading when there is a temperature change and because of this, readings of the new temperature can be read.
So, why mercury can be used as a material in thermometers? It is because it expands while heated. Remember that it is a liquid and it has the capability to expand.
And its coefficient of expansion is nearly constant-that is, the change in volume for each degree of rise or fall in temperature is the same.
To understand the concept behind expansion, in physics, solids, liquids and gases expand when heated. Since mercury is a metallic liquid, it expands when heated.
And since the mercury will expand when it is heated, therefore, the volume will increase.
Therefore, the volume of a liquid is slightly dependent on temperature.
Let the volume V. be the volume of the liquid when the temperature is T.. When the temperature rises the volume will change (for most liquids the volume will increase)
Providing the temperature increase is not too great the volume of the liquid will change by an amount -
AV = V. B (T-T.)
Where the constant ẞ is the thermal expansion coefficient, which accounts for the different liquids that could possibly be used.
Let us prove that mercury can be used as a temperature medium material through considering the appropriate design of a thermometer.
In designing an expansion thermometer the most important fact to bear in mind is the size of the expansion coefficient; it is always very small.
That means that for any reasonable size thermometer the increase in the volume is very small.
The liquid is contained in a spherical bulb at the bottom of the thermometer.
In order to measure the small change in volume the liquid is made to expand up a thin tube (known as a capillary tube).
The height of the column of liquid which is produced is then given by

h = Volume / Area = BV (T-T)/A
In order to make h as large as possible (so that it can be easily measured) we would like the following

1. The expansion coefficient to be as large as possible. Alcohol is therefore better than mercury.


2. The original volume to be as large as possible, without the thermometer becoming unwieldy


3. The area of the capillary tube (and so also its diameter) to be as small as possible.
   Let us now design a mercury thermometer and let us see if mercury is convenient to use or not. Suppose we design a mercury thermometer with a bulb of volume 1 cm3. We would like to make the capillary narrow, so set the diameter to be 0.3 mm.
   What would be the height of the column of mercury produced if the temperature is raised from 10 °C to 80 °C?
   Change in volume = 1.8 x 10 °C 1 cm3 (80 °C -10 °C) = 0.0126 cm3

• Radius of capillary tube = 1⁄2 diameter = 0.15 mm = 0.015cm • Area of capillary tuber (0.015 cm)2= 0.0007069 cm2 height=0.0126 cm3/0.0007069 cm2 = 17.8 cm
It is very convenient to use mercury in thermometer based on this example because this height of the column is large enough to be measured easily.
Actually Gabriel Fahrenheit invented the mercury-in-glass thermometer in 1714.
And now, this is one of the main reasons why mercury is used. Also, other reasons considered why mercury is used because mercury solidifies or freezes at minus 38.83°C and does not expand upon solidification and therefore will not break the glass tube of the thermometer.
But when a thermometer has nitrogen, this gas may flow down the column and will be trapped there when the temperature increases and thus making the thermometer unusable.
To avoid this thermometer problem, all mercury thermometers must be brought indoors when the temperature falls to minus 37°C. For places where the maximum temperature does not exceed minus 38.83 C, you can use a mercury-thallium alloy thermometer which has a solidification point (freezing point) of minus 61.1°C.
When do you use mercury thermometers? Where do you use mercury-in-glass thermometers? Mercury thermometers are now often used in meteorology only as many countries have banned the use of mercury-in-glass thermometers for medical purposes.
Some thermometers use galinstan, a liquid alloy of gallium, indium and tin in place of mercury.
III. Mercury in Barometers
Barometer is an instrument used for measuring atmospheric pressure, that is, the force exerted on a surface of unit area by the weight of the atmosphere.
Because this force is transmitted equally in all directions through any fluid, it is most easily measured by observing the height of a column of liquid that, by its weight, exactly balances the weight of the atmosphere.
A water barometer is far too large to be used conveniently. Liquid mercury, however, is 13.6 times as heavy as water, and the column of mercury sustained by normal atmospheric pressure is only about 760 mm (about 30 in) high.

Normal, or standard, atmospheric pressure is usually defined at 1013.25 millibars, which is equivalent to 760 mm (29.9213 in) of mercury or 1.03323 kg/sq cm (14.6960 lb/sq in).
An ordinary mercury barometer consists of a glass tube about 840 mm (about 33 in) high, closed at the upper end and open at the lower.
When the tube is filled with mercury and the open end placed in a cup full of the same liquid, the level in the tube falls to a height of about 760 mm (about 30 in) above the level in the cup, leaving an almost perfect vacuum at the top of the tube.
Variations in atmospheric pressure cause the liquid in the tube to rise or fall by small amounts, rarely below 737 mm (29 in) or above 775 mm (30.5 in) at sea level.
When the mercury level is read with a form of gradated scale, known as a vemier attachment, and suitable corrections are made for altitude and latitude (because of the change of gravity), for temperature (because of the expansion or contraction of the mercury), and for the diameter of the tube (because of capillarity), the reading of a mercury barometer is reliable to within 0.1 mm (0.004 in).
Actually, this concept was discovered by Evangelista Toriccelli Italian mathematician and physicist in 1643. A unit of measurement, the torr, which is used by physicists working in near- vacuum conditions to indicate atmospheric density and barometric pressure, is named after Torricelli.
V. Other Uses of Mercury
The use of mercury in fluorescent lamps and mercury batteries has also been significantly reduced as alternatives have been developed.
Perhaps most significant is the substitution of diaphragm cells for traditional mercury cells in chlorine-alkali production, which once accounted for a large percentage of total mercury consumption.