Lead is a heavy, soft, and malleable metal with the lowest melting point of any atomically stable metal. It is a heavy metal that is more dense than most common metals. Lead is a post-transition metal with the atomic number 82 and symbol Pb.
Lead is known to be used by humans for centuries. Metallic lead beads found in Asia Minor date back to 7000-6500 BCE. These beads may represent the earliest examples of smelting. The metal has been mined for over 6000 years, with a known presence throughout history across the world. The Ancient Egyptians utilized lead in the production of items such as cosmetics, glazes, glass, enamels, and as sinking weights for fishing nets. Such applications spread to Ancient Greece, and other civilizations. The Greeks not only knew how to mine the metal, but also knew how to convert it to white lead- a highly valued pigment. Lead was the basis of paints for many centuries.
The Romans implemented lead on a large scale, using it for the production of water pipes, tableware, coffins, and in their coinage and currencies. Lead was also used as coinage, a construction material, and as a writing material across several civilizations. In the Ancient Chinese royal court, lead was used as a contraceptive. It was used in wire drawing by eastern and southern African peoples.
The mining of lead declined in the dark ages, but rose again in medieval times with new applications in printing type, pottery glazes, and use in piping and roofing. Lead was used in the production of stained glass in the 13th century. Although lead was, at the time, more expensive than iron, it became the central material in bullets and firearms.
During the industrial revolution, lead production rates sky-rocketed, which lead to the depletion of Britain's mines in the mid 19th century. Lead was once again in demand for use in plumbing and paints. Increased exposure to lead among the working class led to a rise in lead poisoning cases. This inspired research into the the effects of lead intake and consumption. The United Kingdom implemented the first laws aimed at reducing lead exposure in the 1870s and 1880s.
Further evidence of the harmful nature of lead was discovered in the late 19th and early 20th centuries, which resulted in the phasing out of the material in public use among countries such as the USA and areas in Europe. Legislation to control lead air pollution were introduced in the 1970s in Western Europe and the United States. The main product involving the utilization of lead at the end of the 20th century was the lead-acid battery. The production of lead continues to increase worldwide because of this use in lead-acid batteries.
When freshly exposed, lead is silvery-blue in appearance. After exposure to air, the metal tarnishes to a dull grey color. Lead is a relatively poor conductor, but is very soft and can easily be worked into sheets. Lead and lead oxides tend to form covalent bonds, reacting with both acids and bases. Lead tends to bond with itself, which results in the formation of polyhedral structures and chains.
Whether inhaled or swallowed, lead is a highly poisonous metal that affects almost every organ and system in the human body. Although known for centuries, this toxicity wasn't recognized until the late 19th century. Lead is a neurotoxin that accumulates in bones and soft tissues. It can create an interference with biological enzymes, creating neurological damage. The extend of this damage can result in neurological disorders such as behavioral problems and brain damage. Although this toxicity is known, many countries still allow for the use and sale of lead in products such as paint and bullets.
Lead is usually found combined with sulfur, it does not occur naturally in its pure state. Lead is highly abundant in the earth's crust, ranked as the crust's 38th most abundant element. Often found with sphalerite (ZnS), a zinc ore, the main lead-bearing source is an ore called galena (PbS). Because of their close occurrence, lead and zinc are often mined together. They often contain other valuable metals including gold, silver, and copper. Most lead minerals are related to galena, whether they are an oxidation of galena, a decomposition product, or other.
World lead resources are documented as exceeding two billion tons. Some of the most significant lead deposits are located in Australia, China, Ireland, Mexico, Peru, Portugal, Russia, and the United States. Global reserves, or that which is economically feasible to extract, totaled 88 million tons as of 2016. Of this, Australia accounted for 35 million, China 17 million, and Russia 6.4 million.
The metal's low melting point, ductility, high density, and relative inertness, are useful mechanical characteristics. Although some metals are more superior in these traits, lead is much more common. Lead's low melting point, dense nature, and inexpensive state has rendered it ideal for the production of small arms ammunition. Lead has been used to make bullets since their invention in the middle ages. To this day, the metal remains one of the main materials used in bullets.
Lead is, to this day, widely used in the battery industry, cable sheathing, ammunition, pigments, weights for lifting and scuba diving, radiation protection, lead crystal glass, and radiation protection. It is sometimes used for roofing and stained glass windows, and is often used to store corrosive liquids. Lead is used in sculpture and statues, and is often used as a protective sheath for underwater cables due to its resistance to corrosion.
Lead is added to copper alloys, such as bronze and brass to improve machinability and lubricating qualities. The largest use of lead in the 21st century continues to be its role in the production of lead-acid batteries.
There are two main categories of lead production- the primary source is that from mined ores, with the second being scrap metal. Most lead ores contain a small percentage of lead, usually about 3-8%, that must be concentrated for extraction. During the initial process, ores undergo a process of grinding, crushing, froth floatation, dense-medium separation, and drying. This process results in a concentrate that is composed of 30-80% lead by mass. This concentrate is then turned into an impure lead metal. Molten lead produces base lead bullion that is 95 – 99% pure, a level of quality required for trade. Further refining in drossing kettles removes additional impurities. After the impurities have been removed and the lead has been cooled, it is cast into blocks that may weigh as much as a ton.
There are two main methods used in primary production: the first consists of a two-stage process involving roasting, which is followed by blast furnace extraction. This is carried out in separate vessels. The second is a direct process in which extraction takes place in a single vessel. Smelting, an essential component of primary production, only occurs when metallic lead has undergone significant oxidation. Research towards a cleaner process that requires less energy continues. Recycling accounts or 50% of all lead production in Europe and the United States.
The properties of lead, tied with its role in battery making, places significant value on the metal. Today, the top three producers of lead are China, Australia, and the USA, with the top three deposits/ reserve holders being AUS, China, and Russia. Global lead stock levels are tracked on The London Metals Exchange (LME). Traders and investors follow statistics and lead futures closely.
The London Metal Exchange (LME) is the world center for industrial metals trading and other commodities. The LME offers contracts with daily expiry dates of up to three months. Market participants may also partake in weekly contracts of up to six months, and monthly contracts. It also allows for trade in cash, offers worldwide reference pricing, hedging, and the option of physical delivery for settling contracts. The standard contract has a size of 25 tons.
Five main factors largely shape the price of lead. These factors include global stocks, Chinese demand, demand outlook, health concerns, and competing technologies. China utilizes over 40% of the annual global lead supply. Lead prices largely depend on Chinese demand for things like power storage devices and batteries. 85% of lead demand revolves around the battery industry. China and India have begun trading in smart grid technology, which has led to an expansion in the utilization of lead-acid batteries in hybrid and electric vehicles.
In 2007, the price of lead hit an all time high of more than $1.75 per lb. Prior to that rise, the price was fairly stable around $0.25 per lb. For the past ten years lead prices have tended to fluctuate between $0.75 and $1.25 USD per pound.
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