Mercury - Hg

Mercury

Symbol	Hg
Atomic Number	80
Atomic Mass	200.59 g.mol -1
Discovered by	The Ancients

Table of Contents

• What is Mercury?
• Density of Mercury
• Symbol of Mercury in Periodic Table
• Mercury Physical Properties
• Mercury Chemical Properties
• Mercury Element Facts
• Uses of Mercury
• Solved Example
• Frequently Asked Questions – FAQs

What is Mercury?

Mercury is a chemical element and the only common metal which is liquid at ordinary temperatures. It is commonly known as quicksilver and is heavy, silvery-white liquid metal. Mercury is a transition metal.

As a chemical element, mercury cannot be created or destroyed. The same amount has existed on the planet since the earth was formed. Mercury, however, can cycle in the environment as part of both natural and human activities. Mercury metal also found many new applications in electrical devices and electrochemistry. Mercury metal is a volatile liquid; it has a measurable vapour pressure at room temperature.

The density of mercury is 13.6 g.cm^-3 at 20°C

Mercury is a liquid metallic element with many useful applications. It is also an element with properties hazardous to the environment and workplace, and corrosive to many materials. Knowledge of the solubility of mercury is useful in addressing problems requiring knowledge of the concentration of the metals in the liquids and the vapours of our surroundings.

Density of Mercury

Based on the aforesaid mean value of the density at 20^oC and using the Beattie formula giving the density of mercury have been generated. Apart from thermometry, mercury is used as a reference standard for determining the volume of small capacity measures and to maintain the primary standard barometer. In either case, the temperature range of interest is 0-41^oC, so the density values have been calculated in steps of 0.1^oC in this range. The value for the density of mercury refers to an ambient pressure of 101325 Pa. 

The density of mercury at 20 degree C is 13545.848 kg/m³.

Mercury element has been known for thousands of years. People learned to make this metal from the most important ore called Cinnabar. The Cinnabar releases mercury as a vapour when heated; later the vapour is cooled and captured as liquid mercury.

Representation of mercury metal

Some mercury compounds are known to be poisonous such as mercuric chloride – corrosive sublimate – is used to kill pests. While, some compounds are used for medicines like mercurous chloride – calomel – is used to cure skin rashes.

Symbol of Mercury in Periodic Table

Mercury element in the periodic table is symbolized as Hg.

Mercury Physical Properties

Mercury metal can be frozen and changed into a solid at a temperature of –38.85°C. It can be transformed into a gas when boiled at 365.6°C. The density of mercury is 13.59 grams per cubic centimetre.

It has two physical properties of special interest.

• Very high surface tension.
• Very good conductor of electricity.

Surface tension is a property of liquids that makes them act like they are covered with skin. While being a good conductor of electricity, this property is used in a mercury switch kind of turns light on and off.

The other liquid metal is mercury. There is in fact only another liquid element, bromine. Bromine is a non-metallic substance. At a temperature of-38.85 °C (– 37.93 °F), mercury can be frozen (changed into a solid). At 365.6 °C (690.1 °F), it can be transformed into a gas (“boiled”). Its density is 13.59 grams per centimetre cube.

Mercury is a very good electricity conductor, too. In a variety of functional products, this property is used. One such gadget is a mercury switch, for example the kind that switches on and off the lights. You should put a small amount of mercury into a tiny glass capsule.

In order to tip back and forth, the capsule may be made. The mercury runs from one end to the other as it tips. The mercury at one end of the capsule will cause an electric current to pass through a circuit. On the other hand, no mercury is present, so no current will pass. Mercury switches are simple and very quick to produce.

Mercury Chemical Properties

Mercury is moderately active. It does not react with oxygen in the air. It reacts with some acids when they are hot, but not with most cold acids.

Mercury Element Facts

• Mercury is also a chemical element. Its common name is “quicksilver”. The element mercury is silver in colour. It can change very quickly.
• Mercury is used in thermometers, mercury changes when the temperature changes. It expands or becomes larger at high temperatures. It contracts or becomes smaller at low temperatures.
• Once mercury gets into the body has a hard time getting rid of. Many rivers and streams are polluted with mercury.
• Mercury is used in making lights and batteries. It is used in electrical switches. It is also in rat poisons and insecticides. It can also be used in medicine.

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.

Solved Example on Density of Mercury

Question: 

A 20ml sample of mercury has a mass of 271g. Calculate the density of mercury.

Solution:

Density = Mass/volume 

Density = 271g/20ml

Density of mercury element = 13.55 g/ml

This question tests the knowledge of a basic equation. Though the equation is simple, one should be able to manipulate this equation so that one can connect this piece of information with other facts and formulas that are given in the passage.