In economics, inflation is a sustained increase in the general price level of goods and services in an economy over a period of time. When the general price level rises, each unit of currency buys services; the measure of inflation is the inflation rate, the annualized percentage change in a general price index the consumer price index, over time. The opposite of inflation is deflation. Inflation affects economies in various negative ways; the negative effects of inflation include an increase in the opportunity cost of holding money, uncertainty over future inflation which may discourage investment and savings, if inflation were rapid enough, shortages of goods as consumers begin hoarding out of concern that prices will increase in the future. Positive effects include reducing unemployment due to nominal wage rigidity, allowing the central bank more leeway in carrying out monetary policy, encouraging loans and investment instead of money hoarding, avoiding the inefficiencies associated with deflation.
Economists believe that the high rates of inflation and hyperinflation are caused by an excessive growth of the money supply. Views on which factors determine low to moderate rates of inflation are more varied. Low or moderate inflation may be attributed to fluctuations in real demand for goods and services, or changes in available supplies such as during scarcities. However, the consensus view is that a long sustained period of inflation is caused by money supply growing faster than the rate of economic growth. Today, most economists favor a steady rate of inflation. Low inflation reduces the severity of economic recessions by enabling the labor market to adjust more in a downturn, reduces the risk that a liquidity trap prevents monetary policy from stabilizing the economy; the task of keeping the rate of inflation low and stable is given to monetary authorities. These monetary authorities are the central banks that control monetary policy through the setting of interest rates, through open market operations, through the setting of banking reserve requirements.
Rapid increases in the quantity of money or in the overall money supply have occurred in many different societies throughout history, changing with different forms of money used. For instance, when gold was used as currency, the government could collect gold coins, melt them down, mix them with other metals such as silver, copper, or lead, reissue them at the same nominal value. By diluting the gold with other metals, the government could issue more coins without increasing the amount of gold used to make them; when the cost of each coin is lowered in this way, the government profits from an increase in seigniorage. This practice would increase the money supply but at the same time the relative value of each coin would be lowered; as the relative value of the coins becomes lower, consumers would need to give more coins in exchange for the same goods and services as before. These goods and services would experience a price increase. Song Dynasty China introduced the practice of printing paper money to create fiat currency.
During the Mongol Yuan Dynasty, the government spent a great deal of money fighting costly wars, reacted by printing more money, leading to inflation. Fearing the inflation that plagued the Yuan dynasty, the Ming Dynasty rejected the use of paper money, reverted to using copper coins. Large infusions of gold or silver into an economy led to inflation. From the second half of the 15th century to the first half of the 17th, Western Europe experienced a major inflationary cycle referred to as the "price revolution", with prices on average rising sixfold over 150 years; this was caused by the sudden influx of gold and silver from the New World into Habsburg Spain. The silver spread throughout a cash-starved Europe and caused widespread inflation. Demographic factors contributed to upward pressure on prices, with European population growth after depopulation caused by the Black Death pandemic. By the nineteenth century, economists categorized three separate factors that cause a rise or fall in the price of goods: a change in the value or production costs of the good, a change in the price of money, a fluctuation in the commodity price of the metallic content in the currency, currency depreciation resulting from an increased supply of currency relative to the quantity of redeemable metal backing the currency.
Following the proliferation of private banknote currency printed during the American Civil War, the term "inflation" started to appear as a direct reference to the currency depreciation that occurred as the quantity of redeemable banknotes outstripped the quantity of metal available for their redemption. At that time, the term inflation referred to the devaluation of the currency, not to a rise in the price of goods; this relationship between the over-supply of banknotes and a resulting depreciation in their value was noted by earlier classical economists such as David Hume and David Ricardo, who would go on to examine and debate what effect a currency devaluation has on the price of goods. The adoption of fiat currency by many countries, from the 18th century onwards, made much larger variations in the supply of money possible. Rapid increases in the money supply have taken place a number of times in countries experiencing political crises, produ
The kip is the currency of Laos since 1952. One kip was divided into 100 att. In 1945–1946, the Free Lao government in Vientiane issued a series of paper money in denominations of 10, 20 and 50 att and 10 kip before the French authorities took control of the region; the kip was reintroduced in 1952. The kip was sub-divided into cents. Coins were issued in denominations of 10, 20 and 50 att or cents with Lao inscriptions. All had a hole in the centre, like the Chinese cash coins; the only year of issue was 1952. In 1953, the Laos branch of the Institut d'Emission des Etats du Cambodge, du Laos et du Vietnam issued notes dual denominated in piastre and kip. At the same time, the two other branches had the similar arrangement with the riel in Cambodia and the đồng in South Vietnam. There were notes for 5, 100 and 100 kip/piastres. In 1957, the government issued notes denominated in kip; the notes were for 1, 5, 10, 20 and 50 kip printed by the Security Banknote Company, 100 kip printed by the Banque de France and a commemorative 500 kip printed by Thomas De la Rue.
1 and 5 kip notes printed by Bradbury & Wilkinson, a 10 kip by De la Rue were introduced by 1962. In 1963, 20, 50, 200 and 1000 kip notes were added, all printed by De la Rue; these were followed by 500 and 5000 kip notes in 1974 -- 75, again by De La Rue. A 1975 10 kip by Bradbury & Wilkinson and a 1000 kip by De la Rue were printed but not circulated; the Pathet Lao kip was introduced sometime before 1976 in the areas which were under the control of the Pathet Lao. Banknote denominations of 1, 10, 20, 50, 100, 200 and 500 kip were issued; the notes were printed in China. In 1976, the Pathet Lao kip replaced the Royal kip throughout Laos following the Pathet Lao's take over of the country; the exchange rate between the two kip was 1 Pathet Lao kip = 20 royal kip. On 16 December 1979, the old Pathet Lao “Liberation” kip was replaced by the new Lao kip at a rate of 100 to 1. Coins were again issued in Laos for the first time in 28 years in 1980 with denominations of 10, 20 and 50 att, with each being struck in aluminum and depicting the state emblem on the obverse and agricultural themes on the reverse.
These were followed by commemorative 1, 5, 10, 20 and 50 kip in 1985 for the 10 year anniversary of the Lao People's Democratic Republic. However, due to the economic toll of the Soviet collapse in 1991 and the persistence of chronic inflation, there are no coins in circulation in Laos. In 1979, banknotes were introduced in denominations of 1, 5, 10, 20, 50 and 100 kip. 500 kip notes were added in 1988, followed by 1000 kip in 1992, 2000 and 5000 kip in 1997, 10,000 and 20,000 kip in 2002 and 50,000 kip on January 17, 2006. On November 15, 2010 a 100,000 kip banknote was issued to commemorate the 450th anniversary of the founding of the capital and the 35th anniversary of the establishment of the Lao People's Democratic Republic. Kaysone Phomvihane is pictured on the obverse of the 2,000, 5,000, 10,000, 20,000, 50,000, 100,000 kip banknotes; the Bank of Laos governor announced on January 25, 2012 that the Bank of Laos would issue 100,000 Kip banknotes as a regular issue on February 1, 2012 to encourage Lao people to use the national currency instead of U.
S. dollars and Thai baht
Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. In early days, electricity was considered as being not related to magnetism. On, many experimental results and the development of Maxwell's equations indicated that both electricity and magnetism are from a single phenomenon: electromagnetism. Various common phenomena are related to electricity, including lightning, static electricity, electric heating, electric discharges and many others; the presence of an electric charge, which can be either positive or negative, produces an electric field. The movement of electric charges produces a magnetic field; when a charge is placed in a location with a non-zero electric field, a force will act on it. The magnitude of this force is given by Coulomb's law. Thus, if that charge were to move, the electric field would be doing work on the electric charge, thus we can speak of electric potential at a certain point in space, equal to the work done by an external agent in carrying a unit of positive charge from an arbitrarily chosen reference point to that point without any acceleration and is measured in volts.
Electricity is at the heart of many modern technologies, being used for: electric power where electric current is used to energise equipment. Electrical phenomena have been studied since antiquity, though progress in theoretical understanding remained slow until the seventeenth and eighteenth centuries. Practical applications for electricity were few, it would not be until the late nineteenth century that electrical engineers were able to put it to industrial and residential use; the rapid expansion in electrical technology at this time transformed industry and society, becoming a driving force for the Second Industrial Revolution. Electricity's extraordinary versatility means it can be put to an limitless set of applications which include transport, lighting and computation. Electrical power is now the backbone of modern industrial society. Long before any knowledge of electricity existed, people were aware of shocks from electric fish. Ancient Egyptian texts dating from 2750 BCE referred to these fish as the "Thunderer of the Nile", described them as the "protectors" of all other fish.
Electric fish were again reported millennia by ancient Greek and Arabic naturalists and physicians. Several ancient writers, such as Pliny the Elder and Scribonius Largus, attested to the numbing effect of electric shocks delivered by catfish and electric rays, knew that such shocks could travel along conducting objects. Patients suffering from ailments such as gout or headache were directed to touch electric fish in the hope that the powerful jolt might cure them; the earliest and nearest approach to the discovery of the identity of lightning, electricity from any other source, is to be attributed to the Arabs, who before the 15th century had the Arabic word for lightning ra‘ad applied to the electric ray. Ancient cultures around the Mediterranean knew that certain objects, such as rods of amber, could be rubbed with cat's fur to attract light objects like feathers. Thales of Miletus made a series of observations on static electricity around 600 BCE, from which he believed that friction rendered amber magnetic, in contrast to minerals such as magnetite, which needed no rubbing.
Thales was incorrect in believing the attraction was due to a magnetic effect, but science would prove a link between magnetism and electricity. According to a controversial theory, the Parthians may have had knowledge of electroplating, based on the 1936 discovery of the Baghdad Battery, which resembles a galvanic cell, though it is uncertain whether the artifact was electrical in nature. Electricity would remain little more than an intellectual curiosity for millennia until 1600, when the English scientist William Gilbert wrote De Magnete, in which he made a careful study of electricity and magnetism, distinguishing the lodestone effect from static electricity produced by rubbing amber, he coined the New Latin word electricus to refer to the property of attracting small objects after being rubbed. This association gave rise to the English words "electric" and "electricity", which made their first appearance in print in Thomas Browne's Pseudodoxia Epidemica of 1646. Further work was conducted in the 17th and early 18th centuries by Otto von Guericke, Robert Boyle, Stephen Gray and C. F. du Fay.
In the 18th century, Benjamin Franklin conducted extensive research in electricity, selling his possessions to fund his work. In June 1752 he is reputed to have attached a metal key to the bottom of a dampened kite string and flown the kite in a storm-threatened sky. A succession of sparks jumping from the key to the back of his hand showed that lightning was indeed electrical in nature, he explained the paradoxical behavior of the Leyden jar as a device for storing large amounts of electrical charge in terms of electricity consisting of both positive and negative charges. In 1791, Luigi Galvani published his discovery of bioelectromagnetics, demonstrating that electricity was the medium by which neurons passed signals to the muscles. Alessandro Volta's battery, or voltaic pile, of 1800, made from alternating layers of zinc and copper, provided scientists with a more reliable source of electrical energy than the electrostatic machines used; the recognition of electromagnetism, the unity of electric
The Kunming–Singapore railway called the Pan-Asia railway Network is a network of railways, being planned or under construction, that would connect China and all the countries of mainland Southeast Asia. The concept originated with British and French imperialists, who sought to link the railways they had built in southwest China and Malaya, but international conflicts in the 20th century kept regional railways fragmented; the idea was formally revived in October 2006 when 18 Asian and Eurasian countries signed the Trans-Asian railway Network Agreement, which designates the Kunming–Singapore railway as one of several planned trans-Asian railways. The proposed network consists of three main routes from Kunming, China to Bangkok, Thailand: the Eastern route via Vietnam and Cambodia; the southern half of the network from Bangkok to Singapore has long been operational, though a high-speed line has been proposed. As of January 2014, construction of sections connecting China with Vietnam, China with Myanmar and Laos with Vietnam are under way.
Work on sections in Laos began in December 2017 and is expected to be completed in 2021 with Chinese assistance. Those sections are expected to be completed in 2020; the railway network is expected to increase regional economic integration and increase China's economic ties with Southeast Asia. A high-speed rail project in Vietnam with Japanese support was canceled in 2010 due to high cost; however it will be re-considered during 2019 communist party session, as Vietnam’s economy is growing at much faster pace than anticipated. The British and French Empires first proposed building a railway from Kunming to Singapore in 1900 as Russia was completing the Trans-Siberian railway. From 1904 to 1910, the French built the Yunnan–Vietnam railway, to connect Kunming with Hanoi and Haiphong in French Tonkin, now northern Vietnam. In 1918, the southern line of the Thailand railway system was connected with British Malaya's west coast line, completing a metre gauge rail link from Bangkok to Singapore. In the late-1930s, the British began to build the Yunnan–Burma railway but abandoned the effort in 1941 with the outbreak of World War II.
In 1936, the Vietnam's main railway, from Hanoi to Saigon was completed. This French-built system was metre-gauge. In 1942, the railways of Thailand and Cambodia were connected linking Bangkok and Phnom Penh, but this trans-border connection has long since fallen into disuse; the Japanese Empire built the infamous Thailand–Burma railway using prisoners of war to connect Bangkok and Yangon, but the entire line never entered commercial operation and is now submerged by the reservoir behind the Vajiralongkorn Dam. A continuous metre-gauge rail line from Kunming to Singapore via Hanoi, Phnom Penh and Kuala Lumpur was not realized as the French never built the "missing link" between Phnom Penh and Saigon, choosing to build a highway instead. In 2000, ASEAN proposed completing the Kunming to Singapore railway, via Hanoi, Ho Chi Minh City, Phnom Penh, Bangkok; this 5,500 km route is now known as the eastern route. In 2004, ASEAN and China proposed the shorter western route, which instead of running east through Vietnam and Cambodia, would go west from Kunming to Myanmar and to Bangkok.
In 2007 ASEAN and China proposed building three routes, the Eastern, Western and a central route via Laos. In China Kunming–Hai Phong railway, 465 km metre gauge railway from Kunming to the Hekou Yao Autonomous County on the border with Vietnam. Kunming–Yuxi railway, 55.5 km standard gauge railway from Kunming to Yuxi. Yuxi–Mengzi railway, 141 km standard gauge railway from Yuxi to Mengzi. Mengzi–Hekou railway, 140 km standard gauge railway from Mengzi to Hekou. In Vietnam Kunming–Hai Phong railway, metre gauge railway from Lao Cai, on the border with China, to Haiphong via Hanoi. North–South railway of Vietnam, metre gauge railway from Hanoi to Ho Chi Minh City. North–South express railway of Vietnam, 1,570 km standard gauge, high-speed rail, from Hanoi to Ho Chi Minh City; this line was jointly planned by Vietnam and Japan using Shinkansen bullet train technology and financed in part by Japanese official development assistance. The project was scheduled to be built in stages from 2011 to 2020.
In June 2010, Vietnam's National Assembly rejected the plan due to high construction cost equal to about 50 percent of the country's GDP. However, the project will be re-considered during 2019 Vietnam's National Assembly Session as Vietnam’s economy is growing much faster, thus decreasing the project’s cost / GDP ratio. In Laos Savannakhet–Lao Bao railway, a 220 km, electrified double track, high-speed railway from Savannakhet in Savannakhet Province, on the Thai border, to Lao Bảo in Vietnam's Quảng Trị Province; the project is being built by the Giant Consolidated of Malaysia. A ground breaking ceremony was held in Ban Naxai on December 18, 2013; this line will be extended to the port city of Danang in Vietnam, give landlocked Laos an outlet to the South China Sea. In Cambodia The disconnected rail link from Phnom Penh to Ho Chi Minh City is being reconsidered; the cost for construction is estimated around US$600 million and the Chinese government will fund most proportion of construction. The Cambodian government will deal with the relocation of people who will be affected by the proposed new railway construction.
The section from Phnom Penh to the Thai border was completed on July 5, 201
Coffee is a brewed drink prepared from roasted coffee beans, the seeds of berries from certain Coffea species. The genus Coffea is native to tropical Africa and Madagascar, the Comoros, Réunion in the Indian Ocean. Coffee plants are now cultivated in over 70 countries in the equatorial regions of the Americas, Southeast Asia, Indian subcontinent, Africa; the two most grown are C. arabica and C. robusta. Once ripe, coffee berries are picked and dried. Dried coffee seeds are roasted to varying degrees, depending on the desired flavor. Roasted beans are ground and brewed with near-boiling water to produce the beverage known as coffee. Coffee is darkly colored, bitter acidic and has a stimulating effect in humans due to its caffeine content, it is one of the most popular drinks in the world, it can be prepared and presented in a variety of ways. It is served hot, although iced coffee is a popular alternative. Clinical studies indicate that moderate coffee consumption is benign or mildly beneficial in healthy adults, with continuing research on whether long-term consumption lowers the risk of some diseases, although those long-term studies are of poor quality.
The earliest credible evidence of coffee-drinking appears in modern-day Yemen in southern Arabia in the middle of the 15th century in Sufi shrines. It was here in Arabia that coffee seeds were first roasted and brewed in a similar way to how it is now prepared, but the coffee seeds had to be first exported from East Africa to Yemen, as the Coffea arabica plant is thought to have been indigenous to the former. The Yemenis began to cultivate the seed. By the 16th century, the drink had reached Persia and North Africa. From there, it spread to the rest of the world; as of 2016, Brazil was the leading grower of producing one-third of the world total. Coffee is a major export commodity, it is one of the most valuable commodities exported by developing countries. Green, unroasted coffee is one of the most traded agricultural commodities in the world; some controversy has been associated with coffee cultivation and the way developed countries trade with developing nations, as well as the impact on the environment with regards to the clearing of land for coffee-growing and water use.
The markets for fair trade and organic coffee are expanding, notably in the USA. The word coffee appears to have derived from the name of the region where coffee beans were first used by a herder in the 6th or 9th century: kaffa derived from Kaffa Province, the name of the region in ancient Abyssinia; the word "coffee" entered the English language in 1582 via the Dutch koffie, borrowed from the Ottoman Turkish kahve, borrowed in turn from the Arabic qahwah. The Arabic word qahwah was traditionally held to refer to a type of wine whose etymology is given by Arab lexicographers as deriving from the verb qahiya, "to lack hunger", in reference to the drink's reputation as an appetite suppressant, it has been proposed that the source may be the Proto-Central Semitic root q-h-h meaning "dark". The term "coffee pot" dates from 1705; the expression "coffee break" was first attested in 1952. According to legend, ancestors of today's Oromo people in a region of Kaffa in Ethiopia were believed to have been the first to recognize the energizing effect of the coffee plant.
However, there is no direct evidence, found earlier than the 15th century indicating where in Africa coffee first grew or who among the native populations might have used it as a stimulant. The story of Kaldi, the 9th-century Ethiopian goatherd who discovered coffee when he noticed how excited his goats became after eating the beans from a coffee plant, did not appear in writing until 1671 and is apocryphal. Other accounts attribute the discovery of coffee to Sheikh Omar. According to an ancient chronicle, known for his ability to cure the sick through prayer, was once exiled from Mocha in Yemen to a desert cave near Ousab. Starving, Omar found them to be bitter, he tried roasting the seeds to improve the flavor. He tried boiling them to soften the seed, which resulted in a fragrant brown liquid. Upon drinking the liquid Omar was sustained for days; as stories of this "miracle drug" reached Mocha, Omar was made a saint. The earliest credible evidence of coffee-drinking or knowledge of the coffee tree appears in the middle of the 15th century in the accounts of Ahmed al-Ghaffar in Yemen.
It was here in Arabia that coffee seeds were first roasted and brewed, in a similar way to how it is prepared now. Coffee was used by Sufi circles to stay awake for their religious rituals. Accounts differ on the origin of the coffee plant prior to its appearance in Yemen. From Ethiopia, coffee could have been introduced to Yemen via trade across the Red Sea. One account credits Muhammad Ibn Sa'd for bringing the beverage to Aden from the African coast. Other early accounts say Ali ben Omar of the Shadhili Sufi order was the first to introduce coffee to Arabia. According to al Shardi, Ali ben Omar may have encountered coffee during his stay with the Adal king Sadadin's companions in 1401. Famous 16th-century Islamic scholar Ibn Hajar al-Haytami notes in his
Gold is a chemical element with symbol Au and atomic number 79, making it one of the higher atomic number elements that occur naturally. In its purest form, it is a bright reddish yellow, soft and ductile metal. Chemically, gold is a group 11 element, it is solid under standard conditions. Gold occurs in free elemental form, as nuggets or grains, in rocks, in veins, in alluvial deposits, it occurs in a solid solution series with the native element silver and naturally alloyed with copper and palladium. Less it occurs in minerals as gold compounds with tellurium. Gold is resistant to most acids, though it does dissolve in aqua regia, a mixture of nitric acid and hydrochloric acid, which forms a soluble tetrachloroaurate anion. Gold is insoluble in nitric acid, which dissolves silver and base metals, a property that has long been used to refine gold and to confirm the presence of gold in metallic objects, giving rise to the term acid test. Gold dissolves in alkaline solutions of cyanide, which are used in mining and electroplating.
Gold dissolves in mercury, forming amalgam alloys. A rare element, gold is a precious metal, used for coinage and other arts throughout recorded history. In the past, a gold standard was implemented as a monetary policy, but gold coins ceased to be minted as a circulating currency in the 1930s, the world gold standard was abandoned for a fiat currency system after 1971. A total of 186,700 tonnes of gold exists above ground, as of 2015; the world consumption of new gold produced is about 50% in jewelry, 40% in investments, 10% in industry. Gold's high malleability, resistance to corrosion and most other chemical reactions, conductivity of electricity have led to its continued use in corrosion resistant electrical connectors in all types of computerized devices. Gold is used in infrared shielding, colored-glass production, gold leafing, tooth restoration. Certain gold salts are still used as anti-inflammatories in medicine; as of 2017, the world's largest gold producer by far was China with 440 tonnes per year.
Gold is the most malleable of all metals. It can be drawn into a monoatomic wire, stretched about twice before it breaks; such nanowires distort via formation and migration of dislocations and crystal twins without noticeable hardening. A single gram of gold can be beaten into a sheet of 1 square meter, an avoirdupois ounce into 300 square feet. Gold leaf can be beaten thin enough to become semi-transparent; the transmitted light appears greenish blue, because gold reflects yellow and red. Such semi-transparent sheets strongly reflect infrared light, making them useful as infrared shields in visors of heat-resistant suits, in sun-visors for spacesuits. Gold is a good conductor of electricity. Gold has a density of 19.3 g/cm3 identical to that of tungsten at 19.25 g/cm3. By comparison, the density of lead is 11.34 g/cm3, that of the densest element, osmium, is 22.588±0.015 g/cm3. Whereas most metals are gray or silvery white, gold is reddish-yellow; this color is determined by the frequency of plasma oscillations among the metal's valence electrons, in the ultraviolet range for most metals but in the visible range for gold due to relativistic effects affecting the orbitals around gold atoms.
Similar effects impart a golden hue to metallic caesium. Common colored gold alloys include the distinctive eighteen-karat rose gold created by the addition of copper. Alloys containing palladium or nickel are important in commercial jewelry as these produce white gold alloys. Fourteen-karat gold-copper alloy is nearly identical in color to certain bronze alloys, both may be used to produce police and other badges. White gold alloys can be made with nickel. Fourteen- and eighteen-karat gold alloys with silver alone appear greenish-yellow and are referred to as green gold. Blue gold can be made by alloying with iron, purple gold can be made by alloying with aluminium. Less addition of manganese, aluminium and other elements can produce more unusual colors of gold for various applications. Colloidal gold, used by electron-microscopists, is red. Gold has only one stable isotope, 197Au, its only occurring isotope, so gold is both a mononuclidic and monoisotopic element. Thirty-six radioisotopes have been synthesized, ranging in atomic mass from 169 to 205.
The most stable of these is 195Au with a half-life of 186.1 days. The least stable is 171Au. Most of gold's radioisotopes with atomic masses below 197 decay by some combination of proton emission, α decay, β+ decay; the exceptions are 195Au, which decays by electron capture, 196Au, which decays most by electron capture with a minor β− decay path. All of gold's radioisotopes with atomic masses above 197 decay by β− decay. At least 32 nuclear isomers have been characterized, ranging in atomic mass from 170 to 200. Within that range, only 178Au, 180Au, 181Au, 182Au, 188Au do not have isomers. Gold's most stable isomer is 198m2Au with a half-life of 2.27 days. Gold's least stable isomer is 177m2Au with a half-life of only 7 ns. 184m1Au has three decay paths: β+ decay, isomeric
Natural rubber called India rubber or caoutchouc, as produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds, plus water. Thailand and Indonesia are two of the leading rubber producers. Forms of polyisoprene that are used as natural rubbers are classified as elastomers. Rubber is harvested in the form of the latex from the rubber tree or others; the latex is a sticky, milky colloid drawn off by making incisions in the bark and collecting the fluid in vessels in a process called "tapping". The latex is refined into rubber ready for commercial processing. In major areas, latex is allowed to coagulate in the collection cup; the coagulated lumps are processed into dry forms for marketing. Natural rubber is used extensively in many applications and products, either alone or in combination with other materials. In most of its useful forms, it has a large stretch ratio and high resilience, is waterproof; the major commercial source of natural rubber latex is the Pará rubber tree, a member of the spurge family, Euphorbiaceae.
This species is preferred. A properly managed tree responds to wounding by producing more latex for several years. Congo rubber a major source of rubber, came from vines in the genus Landolphia. Dandelion milk contains latex; the latex exhibits the same quality as the natural rubber from rubber trees. In the wild types of dandelion, latex content varies greatly. In Nazi Germany, research projects tried to use dandelions as a base for rubber production, but failed. In 2013, by inhibiting one key enzyme and using modern cultivation methods and optimization techniques, scientists in the Fraunhofer Institute for Molecular Biology and Applied Ecology in Germany developed a cultivar, suitable for commercial production of natural rubber. In collaboration with Continental Tires, IME began a pilot facility. Many other plants produce forms of latex rich in isoprene polymers, though not all produce usable forms of polymer as as the Pará; some of them require more elaborate processing to produce anything like usable rubber, most are more difficult to tap.
Some produce other desirable materials, for example chicle from Manilkara species. Others that have been commercially exploited, or at least showed promise as rubber sources, include the rubber fig, Panama rubber tree, various spurges, the related Scorzonera tau-saghyz, various Taraxacum species, including common dandelion and Russian dandelion, most for its hypoallergenic properties, guayule; the term gum rubber is sometimes applied to the tree-obtained version of natural rubber in order to distinguish it from the synthetic version. The first use of rubber was by the indigenous cultures of Mesoamerica; the earliest archeological evidence of the use of natural latex from the Hevea tree comes from the Olmec culture, in which rubber was first used for making balls for the Mesoamerican ballgame. Rubber was used by the Maya and Aztec cultures – in addition to making balls Aztecs used rubber for other purposes such as making containers and to make textiles waterproof by impregnating them with the latex sap.
The Pará rubber tree is indigenous to South America. Charles Marie de La Condamine is credited with introducing samples of rubber to the Académie Royale des Sciences of France in 1736. In 1751, he presented a paper by François Fresneau to the Académie that described many of rubber's properties; this has been referred to as the first scientific paper on rubber. In England, Joseph Priestley, in 1770, observed that a piece of the material was good for rubbing off pencil marks on paper, hence the name "rubber", it made its way around England. In 1764 François Fresnau discovered. Giovanni Fabbroni is credited with the discovery of naphtha as a rubber solvent in 1779. South America remained the main source of latex rubber used during much of the 19th century; the rubber trade was controlled by business interests but no laws expressly prohibited the export of seeds or plants. In 1876, Henry Wickham smuggled 70,000 Pará rubber tree seeds from Brazil and delivered them to Kew Gardens, England. Only 2,400 of these germinated.
Seedlings were sent to India, British Ceylon, Dutch East Indies and British Malaya. Malaya was to become the biggest producer of rubber. In the early 1900s, the Congo Free State in Africa was a significant source of natural rubber latex gathered by forced labor. King Leopold II's colonial state brutally enforced production quotas. Tactics to enforce the rubber quotas included removing the hands of victims to prove they had been killed. Soldiers came back from raids with baskets full of chopped-off hands. Villages that resisted were razed to encourage better compliance locally. See Atrocities in the Congo Free State for more information on the rubber trade in the Congo Free State in the late 1800s and early 1900s. Liberia and Nigeria started production. In India, commercial cultivation was introduced by British planters, although the experimental efforts to grow rubber on a commercial scale were initiated as early as 1873 at the Calcutta Botanical Gardens; the first commercial Hevea plantations were established at Thattekadu in Kerala in 1902.
In years the plantation expanded to Karnataka, Tamil Nadu and the Andaman and Nicobar Islands of India. India today is the