Redox
Redox is a chemical reaction in which the oxidation states of atoms are changed. Any such reaction involves both a reduction process and a complementary oxidation process, two key concepts involved with electron transfer processes. Redox reactions include all chemical reactions; the chemical species from which the electron is stripped is said to have been oxidized, while the chemical species to which the electron is added is said to have been reduced. It can be explained in simple terms: Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom, or ion. Reduction is a decrease in oxidation state by a molecule, atom, or ion; as an example, during the combustion of wood, oxygen from the air is reduced, gaining electrons from carbon, oxidized. Although oxidation reactions are associated with the formation of oxides from oxygen molecules, oxygen is not included in such reactions, as other chemical species can serve the same function; the reaction can occur slowly, as with the formation of rust, or more in the case of fire.
There are simple redox processes, such as the oxidation of carbon to yield carbon dioxide or the reduction of carbon by hydrogen to yield methane, more complex processes such as the oxidation of glucose in the human body. "Redox" is a portmanteau of the words "reduction" and "oxidation". The word oxidation implied reaction with oxygen to form an oxide, since dioxygen was the first recognized oxidizing agent; the term was expanded to encompass oxygen-like substances that accomplished parallel chemical reactions. The meaning was generalized to include all processes involving loss of electrons; the word reduction referred to the loss in weight upon heating a metallic ore such as a metal oxide to extract the metal. In other words, ore was "reduced" to metal. Antoine Lavoisier showed. Scientists realized that the metal atom gains electrons in this process; the meaning of reduction became generalized to include all processes involving a gain of electrons. Though "reduction" seems counter-intuitive when speaking of the gain of electrons, it might help to think of reduction as the loss of oxygen, its historical meaning.
Since electrons are negatively charged, it is helpful to think of this as reduction in electrical charge. The electrochemist John Bockris has used the words electronation and deelectronation to describe reduction and oxidation processes when they occur at electrodes; these words are analogous to protonation and deprotonation, but they have not been adopted by chemists worldwide. The term "hydrogenation" could be used instead of reduction, since hydrogen is the reducing agent in a large number of reactions in organic chemistry and biochemistry. But, unlike oxidation, generalized beyond its root element, hydrogenation has maintained its specific connection to reactions that add hydrogen to another substance; the word "redox" was first used in 1928. The processes of oxidation and reduction occur and cannot happen independently of one another, similar to the acid–base reaction; the oxidation alone and the reduction alone are each called a half-reaction, because two half-reactions always occur together to form a whole reaction.
When writing half-reactions, the gained or lost electrons are included explicitly in order that the half-reaction be balanced with respect to electric charge. Though sufficient for many purposes, these general descriptions are not correct. Although oxidation and reduction properly refer to a change in oxidation state — the actual transfer of electrons may never occur; the oxidation state of an atom is the fictitious charge that an atom would have if all bonds between atoms of different elements were 100% ionic. Thus, oxidation is best defined as an increase in oxidation state, reduction as a decrease in oxidation state. In practice, the transfer of electrons will always cause a change in oxidation state, but there are many reactions that are classed as "redox" though no electron transfer occurs. In redox processes, the reductant transfers electrons to the oxidant. Thus, in the reaction, the reductant or reducing agent loses electrons and is oxidized, the oxidant or oxidizing agent gains electrons and is reduced.
The pair of an oxidizing and reducing agent that are involved in a particular reaction is called a redox pair. A redox couple is a reducing species and its corresponding oxidizing form, e.g. Fe2+/Fe3+ Substances that have the ability to oxidize other substances are said to be oxidative or oxidizing and are known as oxidizing agents, oxidants, or oxidizers; that is, the oxidant removes electrons from another substance, is thus itself reduced. And, because it "accepts" electrons, the oxidizing agent is called an electron acceptor. Oxygen is the quintessential oxidizer. Oxidants are chemical substances with elements in high oxidation states, or else electronegative elements that can gain extra electrons by oxidizing another substance. Substances that have the ability to reduce other substances are said to be reductive or reducing and are known as
Finery forge
A finery forge is a forge used to produce wrought iron, from pig iron by decarburization. The process involved liquifying cast iron in a fining hearth and removing carbon from the molten cast iron through oxidation. Finery forges were used as early as 3rd century BC, based on archaeological evidence found at a site in Tieshengguo, China; the finery forge process was replaced by the puddling process and the roller mill, both developed by Henry Cort in 1783-4, but not becoming widespread until after 1800. A finery forge was used to refine wrought iron at least by the 3rd century BC in ancient China, based on the earliest archaeological specimens of cast and pig iron fined into wrought iron and steel found at the early Han Dynasty site at Tieshengguo. Pigott speculates that the finery forge existed in the previous Warring States period, because of the wrought iron items from China dating to that period and there was no documented evidence of the bloomery being used in China. Wagner writes that in addition to the Han Dynasty hearths believed to be fining hearths, there is pictoral evidence of the fining hearth from a Shandong tomb mural dated 1st to 2nd century AD, as well as a hint of written evidence in the 4th century AD Daoist text Taiping Jing.
In Europe, the concept of the finery forge may have been evident as early as the 13th century. However, it was not capable of being used to fashion plate armor until the 15th century, as described in conjunction with the waterwheel-powered blast furnace by the Florentine Italian engineer Antonio Averlino; the finery forge process began to be replaced in Europe from the late 18th century by others, of which puddling was the most successful, though some continued in use through the mid-19th century. The new methods used mineral fuel, freed the iron industry from its dependence on wood to make charcoal. There were several types of finery forges; the dominant type in Sweden was the German forge, which had a single hearth, used for all processes. In Swedish Uppland north of Stockholm and certain adjacent provinces, another kind known as the Walloon forge was used for the production of a pure kind of iron known as oregrounds iron, exported to England to make blister steel, its purity depended on the use of ore from the Dannemora mine.
The Walloon forge was the only kind used in Great Britain. The forge had two kinds of hearths, the finery to finish the product and the chafery to reheat the bloom, the raw material of the process. In the finery, a workman known as the "finer" remelted pig iron so as to oxidise the carbon; this produced a lump of iron known as a bloom. This was returned to the finery; the next stages were undertaken by the "hammerman", who in some iron-making areas such as South Yorkshire was known as the "stringsmith", who heated his iron in a string-furnace. Because the bloom is porous, its open spaces are full of slag, the hammerman's or stringsmith's tasks were to beat the heated bloom with a hammer to drive the molten slag out of it, to draw the product out into a bar to produce what was known as anconies or bar iron. In order to do this, he had to reheat the iron; the fuel used in the finery had to be charcoal, as impurities in any mineral fuel would affect the quality of the iron. The waste product was allowed to cool in the hearth and removed as a "mosser".
In the Furness district they were left as the capstone of a wall near Spark Bridge and Nibthwaite forges. H. Schubert, History of British Iron and Steel Industry c.450 BC to AD 1775, 272–291. A. den Ouden, "The Production of Wrought Iron in Finery Hearths", Historical Metallurgy 15, 63–87 and 16, 29–33. K-G. Hildebrand, Swedish Iron in the Seventeenth and Eighteenth Centuries: Export Industry Before Industrialization. P. King,'The Cartel in Oregrounds Iron: Trading in the Raw Material for Steel During the 18th century", Journal of Industrial History 6, 25–48
Carbon
Carbon is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds, it belongs to group 14 of the periodic table. Three isotopes occur 12C and 13C being stable, while 14C is a radionuclide, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity. Carbon is the 15th most abundant element in the Earth's crust, the fourth most abundant element in the universe by mass after hydrogen and oxygen. Carbon's abundance, its unique diversity of organic compounds, its unusual ability to form polymers at the temperatures encountered on Earth enables this element to serve as a common element of all known life, it is the second most abundant element in the human body by mass after oxygen. The atoms of carbon can bond together in different ways, termed allotropes of carbon; the best known are graphite and amorphous carbon. The physical properties of carbon vary with the allotropic form.
For example, graphite is opaque and black while diamond is transparent. Graphite is soft enough to form a streak on paper, while diamond is the hardest occurring material known. Graphite is a good electrical conductor. Under normal conditions, carbon nanotubes, graphene have the highest thermal conductivities of all known materials. All carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form at standard temperature and pressure, they are chemically resistant and require high temperature to react with oxygen. The most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and transition metal carbonyl complexes; the largest sources of inorganic carbon are limestones and carbon dioxide, but significant quantities occur in organic deposits of coal, peat and methane clathrates. Carbon forms a vast number of compounds, more than any other element, with ten million compounds described to date, yet that number is but a fraction of the number of theoretically possible compounds under standard conditions.
For this reason, carbon has been referred to as the "king of the elements". The allotropes of carbon include graphite, one of the softest known substances, diamond, the hardest occurring substance, it bonds with other small atoms, including other carbon atoms, is capable of forming multiple stable covalent bonds with suitable multivalent atoms. Carbon is known to form ten million different compounds, a large majority of all chemical compounds. Carbon has the highest sublimation point of all elements. At atmospheric pressure it has no melting point, as its triple point is at 10.8±0.2 MPa and 4,600 ± 300 K, so it sublimes at about 3,900 K. Graphite is much more reactive than diamond at standard conditions, despite being more thermodynamically stable, as its delocalised pi system is much more vulnerable to attack. For example, graphite can be oxidised by hot concentrated nitric acid at standard conditions to mellitic acid, C66, which preserves the hexagonal units of graphite while breaking up the larger structure.
Carbon sublimes in a carbon arc, which has a temperature of about 5800 K. Thus, irrespective of its allotropic form, carbon remains solid at higher temperatures than the highest-melting-point metals such as tungsten or rhenium. Although thermodynamically prone to oxidation, carbon resists oxidation more than elements such as iron and copper, which are weaker reducing agents at room temperature. Carbon is the sixth element, with a ground-state electron configuration of 1s22s22p2, of which the four outer electrons are valence electrons, its first four ionisation energies, 1086.5, 2352.6, 4620.5 and 6222.7 kJ/mol, are much higher than those of the heavier group-14 elements. The electronegativity of carbon is 2.5 higher than the heavier group-14 elements, but close to most of the nearby nonmetals, as well as some of the second- and third-row transition metals. Carbon's covalent radii are taken as 77.2 pm, 66.7 pm and 60.3 pm, although these may vary depending on coordination number and what the carbon is bonded to.
In general, covalent radius decreases with higher bond order. Carbon compounds form the basis of all known life on Earth, the carbon–nitrogen cycle provides some of the energy produced by the Sun and other stars. Although it forms an extraordinary variety of compounds, most forms of carbon are comparatively unreactive under normal conditions. At standard temperature and pressure, it resists all but the strongest oxidizers, it does not react with hydrochloric acid, chlorine or any alkalis. At elevated temperatures, carbon reacts with oxygen to form carbon oxides and will rob oxygen from metal oxides to leave the elemental metal; this exothermic reaction is used in the iron and steel industry to smelt iron and to control the carbon content of steel: Fe3O4 + 4 C → 3 Fe + 4 COCarbon monoxide can be recycled to smelt more iron: Fe3O4 + 4 CO → 3 Fe + 4 CO2with sulfur to form carbon disulfide and with steam in the coal-gas reaction: C + H2O → CO + H2. Carbon combines with some metals at high temperatures to form metallic carbides, such as the iron carbide cementite in steel and tungsten carbide used as an abrasive and for making hard tips for cutting tools.
The system of carbon allotropes spans a range of extremes: Atomic carbon is a ver
Smelting
Smelting is a process of applying heat to ore in order to extract out a base metal. It is a form of extractive metallurgy, it is used to extract many metals from their ores, including silver, iron and other base metals. Smelting uses heat and a chemical reducing agent to decompose the ore, driving off other elements as gases or slag and leaving the metal base behind; the reducing agent is a source of carbon, such as coke—or, in earlier times, charcoal. The carbon removes oxygen from the ore; the carbon thus oxidizes in two stages, producing first carbon monoxide and carbon dioxide. As most ores are impure, it is necessary to use flux, such as limestone, to remove the accompanying rock gangue as slag. Plants for the electrolytic reduction of aluminium are generally referred to as aluminium smelters. Labourers working in the smelting industry have reported respiratory illnesses inhibiting their ability to perform the physical tasks demanded by their jobs. Smelting involves more than just melting the metal out of its ore.
Most ores are the chemical compound of the metal and other elements, such as oxygen, sulfur, or carbon and oxygen together. To extract the metal, workers must make these compounds undergo a chemical reaction. Smelting therefore consists of using suitable reducing substances that combine with those oxidizing elements to free the metal. In the case of carbonates and sulfides, a process called "roasting" drives out the unwanted carbon or sulfur, leaving an oxide, which can be directly reduced. Roasting is carried out in an oxidizing environment. A few practical examples: Malachite, a common ore of copper, is copper carbonate hydroxide Cu22; this mineral undergoes thermal decomposition to 2CuO, CO2, H2O in several stages between 250 °C and 350 °C. The carbon dioxide and water are expelled into the atmosphere, leaving copper oxide, which can be directly reduced to copper as described in the following section titled Reduction. Galena, the most common mineral of lead, is lead sulfide; the sulfide is oxidized to a sulfite, which thermally decomposes into lead oxide and sulfur dioxide gas.
The sulfur dioxide is expelled, the lead oxide is reduced as below. Reduction is the final, high-temperature step in smelting, in which the oxide becomes the elemental metal. A reducing environment pulls the final oxygen atoms from the raw metal; the required temperature varies over a large range, both in absolute terms and in terms of the melting point of the base metal. Examples: Iron oxide becomes metallic iron at 1250 °C 300 degrees below iron's melting point of 1538 °C. Mercuric oxide becomes vaporous mercury near 550 °C 600 degrees above mercury's melting point of -38 °C. Flux and slag can provide a secondary service after the reduction step is complete: they provide a molten cover on the purified metal, preventing contact with oxygen while still hot enough to oxidize; this prevents impurities from forming in the metal. Metal workers use fluxes in smelting for several purposes, chief among them catalyzing the desired reactions and chemically binding to unwanted impurities or reaction products.
Calcium oxide, in the form of lime, was used for this purpose, since it could react with the carbon dioxide and sulfur dioxide produced during roasting and smelting to keep them out of the working environment. Of the seven metals known in antiquity, only gold occurred in native form in the natural environment; the others – copper, silver, tin and mercury – occur as minerals, though copper is found in its native state in commercially significant quantities. These minerals are carbonates, sulfides, or oxides of the metal, mixed with other components such as silica and alumina. Roasting the carbonate and sulfide minerals in air converts them to oxides; the oxides, in turn, are smelted into the metal. Carbon monoxide was the reducing agent of choice for smelting, it is produced during the heating process, as a gas comes into intimate contact with the ore. In the Old World, humans learned to smelt metals in prehistoric times, more than 8000 years ago; the discovery and use of the "useful" metals — copper and bronze at first iron a few millennia — had an enormous impact on human society.
The impact was so pervasive that scholars traditionally divide ancient history into Stone Age, Bronze Age, Iron Age. In the Americas, pre-Inca civilizations of the central Andes in Peru had mastered the smelting of copper and silver at least six centuries before the first Europeans arrived in the 16th century, while never mastering the smelting of metals such as iron for use with weapon-craft. In the Old World, the first metals smelted were lead; the earliest known cast lead beads were found in the Çatal Höyük site in Anatolia, dated from about 6500 BC, but the metal may have been known earlier. Since the discovery happened several millennia before the invention of writing, there is no written record about how it was made; however and lead can be smelted by placing the ores in a wood fire, leaving the possibility that the discovery may have occurred by accident. Lead is a common metal, but its discovery had little impact in the ancient world, it is too soft to use for structural elements or weapons, though its high density relative to other metals makes it ideal for sling projectiles.
However, since it was
Iron oxide
Iron oxides are chemical compounds composed of iron and oxygen. All together, there are sixteen known iron oxyhydroxides. Iron oxides and oxide-hydroxides are widespread in nature, play an important role in many geological and biological processes, are used by humans, e.g. as iron ores, catalysts, in thermite and hemoglobin. Common rust is a form of iron oxide. Iron oxides are used as inexpensive, durable pigments in paints and colored concretes. Colors available are in the "earthy" end of the yellow/orange/red/brown/black range; when used as a food coloring, it has E number E172. Oxide of FeIIFeO: iron oxide, wüstite FeO2: iron dioxide Mixed oxides of FeII and FeIIIFe3O4: Iron oxide, magnetite Fe4O5 Fe5O6 Fe5O7 Fe25O32 Fe13O19 Oxide of FeIIIFe2O3: iron oxide α-Fe2O3: alpha phase, hematite β-Fe2O3: beta phase γ-Fe2O3: gamma phase, maghemite ε-Fe2O3: epsilon phase iron hydroxide iron hydroxide, akaganéite, feroxyhyte, ferrihydrite, or 5 Fe 2 O 3 ⋅ 9 H 2 O, better recast as FeOOH ⋅ 0.4 H 2 O high-pressure FeOOH schwertmannite green rust Several species of bacteria, including Shewanella oneidensis, Geobacter sulfurreducens and Geobacter metallireducens, metabolically utilize solid iron oxides as a terminal electron acceptor, reducing Fe oxides to Fe containing oxides.
Under conditions favoring iron reduction, the process of iron oxide reduction can replace at least 80% of methane production occurring by methanogenesis. This phenomenon occurs in a nitrogen-containing environment with low sulfate concentrations. Methanogenesis, an Archaean driven process, is the predominate form of carbon mineralization in sediments at the bottom of the ocean. Methanogenesis completes the decomposition of organic matter to methane; the specific electron donor for iron oxide reduction in this situation is still under debate, but the two potential candidates include either Titanium or compounds present in yeast. The predicted reactions with Titanium serving as the electron donor and phenazine-1-carboxylate serving as an electron shuttle is as follows: Ti-cit + CO2 + 8H+ → CH4 + 2H2O + Ti + cit ΔE = –240 + 300 mV Ti-cit + PCA → PCA + Ti + cit ΔE = –116 + 300 mV PCA + Fe3 → Fe2+ + PCA ΔE = –50 + 116 mV Note: cit = citrate. Titanium is oxidized to Titanium; the reduced form of PCA can reduce the iron hydroxide.
On the other hand when airborne, iron oxides have been shown to harm the lung tissues of living organisms by the formation of hydroxyl radicals, leading to the creation of alkyl radicals. The following reactions occur when Fe2O3 and FeO, hereafter represented as Fe3+ and Fe2+ iron oxide particulates accumulate in the lungs. O2 + e− → O2• –The formation of the superoxide anion is catalyzed by a transmembrane enzyme called NADPH oxidase; the enzyme facilitates the transport of an electron across the plasma membrane from cytosolic NADPH to extracellular oxygen to produce O2• –. NADPH and FAD are bound to cytoplasmic binding sites on the enzyme. Two electrons from NADPH are transported to FAD which reduces it to FADH2. One electron moves to one of two heme groups in the enzyme within the plane of the membrane; the second electron pushes the first electron to the second heme group so that it can associate with the first heme group. For the transfer to occur, the second heme must be bound to extracellular oxygen, the acceptor of the electron.
This enzyme can be located within the membranes of intracellular organelles allowing the formation of O2• – to occur within organelles. 2O2• – + 2 H+ → H2O2 + O2 The formation of hydrogen peroxide can occur spontaneously when the environment has a lower pH at pH 7.4. The enzyme superoxide dismutase can catalyze this reaction. Once H2O2 has been synthesized, it can diffuse thro
Bronze
Bronze is an alloy consisting of copper with about 12–12.5% tin and with the addition of other metals and sometimes non-metals or metalloids such as arsenic, phosphorus or silicon. These additions produce a range of alloys that may be harder than copper alone, or have other useful properties, such as stiffness, ductility, or machinability; the archeological period in which bronze was the hardest metal in widespread use is known as the Bronze Age. The beginning of the Bronze Age in India and western Eurasia is conventionally dated to the mid-4th millennium BC, to the early 2nd millennium BC in China; the Bronze Age was followed by the Iron Age starting from about 1300 BC and reaching most of Eurasia by about 500 BC, although bronze continued to be much more used than it is in modern times. Because historical pieces were made of brasses and bronzes with different compositions, modern museum and scholarly descriptions of older objects use the more inclusive term "copper alloy" instead. There are two basic theories as to the origin of the word.
Romance theoryThe Romance theory holds that the word bronze was borrowed from French bronze, itself borrowed from Italian bronzo "bell metal, brass" from either, bróntion, back-formation from Byzantine Greek brontēsíon from Brentḗsion ‘Brindisi’, reputed for its bronze. Proto-Slavic theoryThe Proto-Slavic theory reflects the philological issue that in the most of Slavonic languages word "bronza" corresponds to "war metal" while at the early stages of the Bronze working it was used exclusively for military purposes; the discovery of bronze enabled people to create metal objects which were harder and more durable than possible. Bronze tools, weapons and building materials such as decorative tiles were harder and more durable than their stone and copper predecessors. Bronze was made out of copper and arsenic, forming arsenic bronze, or from or artificially mixed ores of copper and arsenic, with the earliest artifacts so far known coming from the Iranian plateau in the 5th millennium BC, it was only that tin was used, becoming the major non-copper ingredient of bronze in the late 3rd millennium BC.
Tin bronze was superior to arsenic bronze in that the alloying process could be more controlled, the resulting alloy was stronger and easier to cast. Unlike arsenic, metallic tin and fumes from tin refining are not toxic; the earliest tin-alloy bronze dates to 4500 BC in a Vinča culture site in Pločnik. Other early examples date to the late 4th millennium BC in Egypt and some ancient sites in China and Mesopotamia. Ores of copper and the far rarer tin are not found together, so serious bronze work has always involved trade. Tin sources and trade in ancient times had a major influence on the development of cultures. In Europe, a major source of tin was the British deposits of ore in Cornwall, which were traded as far as Phoenicia in the eastern Mediterranean. In many parts of the world, large hoards of bronze artifacts are found, suggesting that bronze represented a store of value and an indicator of social status. In Europe, large hoards of bronze tools socketed axes, are found, which show no signs of wear.
With Chinese ritual bronzes, which are documented in the inscriptions they carry and from other sources, the case is clear. These were made in enormous quantities for elite burials, used by the living for ritual offerings. Though bronze is harder than wrought iron, with Vickers hardness of 60–258 vs. 30–80, the Bronze Age gave way to the Iron Age after a serious disruption of the tin trade: the population migrations of around 1200–1100 BC reduced the shipping of tin around the Mediterranean and from Britain, limiting supplies and raising prices. As the art of working in iron improved, iron improved in quality; as cultures advanced from hand-wrought iron to machine-forged iron, blacksmiths learned how to make steel. Steel holds a sharper edge longer. Bronze was still used during the Iron Age, has continued in use for many purposes to the modern day. There are many different bronze alloys, but modern bronze is 88% copper and 12% tin. Alpha bronze consists of the alpha solid solution of tin in copper.
Alpha bronze alloys of 4–5% tin are used to make coins, springs and blades. Historical "bronzes" are variable in composition, as most metalworkers used whatever scrap was on hand; the proportions of this mixture suggests. The Benin Bronzes are in fact brass, the Romanesque Baptismal font at St Bartholomew's Church, Liège is described as both bronze and brass. In the Bronze Age, two forms of bronze were used: "classic bronze", about 10% tin, was used in
Recycling
Recycling is the process of converting waste materials into new materials and objects. It is an alternative to "conventional" waste disposal that can save material and help lower greenhouse gas emissions. Recycling can prevent the waste of useful materials and reduce the consumption of fresh raw materials, thereby reducing: energy usage, air pollution, water pollution. Recycling is a key component of modern waste reduction and is the third component of the "Reduce and Recycle" waste hierarchy. Thus, recycling aims at environmental sustainability by substituting raw material inputs into and redirecting waste outputs out of the economic system. There are some ISO standards related to recycling such as ISO 15270:2008 for plastics waste and ISO 14001:2015 for environmental management control of recycling practice. Recyclable materials include many kinds of glass, cardboard, plastic, textiles and electronics; the composting or other reuse of biodegradable waste—such as food or garden waste—is a form of recycling.
Materials to be recycled are either delivered to a household recycling center or picked up from curbside bins sorted and reprocessed into new materials destined for manufacturing new products. In the strictest sense, recycling of a material would produce a fresh supply of the same material—for example, used office paper would be converted into new office paper or used polystyrene foam into new polystyrene. However, this is difficult or too expensive, so "recycling" of many products or materials involves their reuse in producing different materials instead. Another form of recycling is the salvage of certain materials from complex products, either due to their intrinsic value, or due to their hazardous nature. Recycling has been a common practice for most of human history, with recorded advocates as far back as Plato in the fourth century BC. During periods when resources were scarce and hard to come by, archaeological studies of ancient waste dumps show less household waste —implying more waste was being recycled in the absence of new material.
In pre-industrial times, there is evidence of scrap bronze and other metals being collected in Europe and melted down for perpetual reuse. Paper recycling was first recorded in 1031. In Britain dust and ash from wood and coal fires was collected by "dustmen" and downcycled as a base material used in brick making; the main driver for these types of recycling was the economic advantage of obtaining recycled feedstock instead of acquiring virgin material, as well as a lack of public waste removal in more densely populated areas. In 1813, Benjamin Law developed the process of turning rags into "shoddy" and "mungo" wool in Batley, Yorkshire; this material combined recycled fibers with virgin wool. The West Yorkshire shoddy industry in towns such as Batley and Dewsbury lasted from the early 19th century to at least 1914. Industrialization spurred demand for affordable materials. Railroads both purchased and sold scrap metal in the 19th century, the growing steel and automobile industries purchased scrap in the early 20th century.
Many secondary goods were collected and sold by peddlers who scoured dumps and city streets for discarded machinery, pots and other sources of metal. By World War I, thousands of such peddlers roamed the streets of American cities, taking advantage of market forces to recycle post-consumer materials back into industrial production. Beverage bottles were recycled with a refundable deposit at some drink manufacturers in Great Britain and Ireland around 1800, notably Schweppes. An official recycling system with refundable deposits was established in Sweden for bottles in 1884 and aluminum beverage cans in 1982. New chemical industries created in the late 19th century both invented new materials and promised to transform valueless into valuable materials. Proverbially, you could not make a silk purse of a sow's ear—until the US firm Arthur D. Little published in 1921 "On the Making of Silk Purses from Sows' Ears", its research proving that when "chemistry puts on overalls and gets down to business... new values appear.
New and better paths are opened to reach the goals desired."Recycling was a major issue for governments throughout World War II. Financial constraints and significant material shortages due to war efforts made it necessary for countries to reuse goods and recycle materials; these resource shortages caused by the world wars, other such world-changing occurrences encouraged recycling. The struggles of war claimed much of the material resources available, leaving little for the civilian population, it became necessary for most homes to recycle their waste, as recycling offered an extra source of materials allowing people to make the most of what was available to them. Recycling household materials meant a better chance of victory. Massive government promotion campaigns, such as the National Salvage Campaign in Britain and the Salvage for Victory campaign in the United States, were carried out on the home front in every combative nation, urging citizens to donate metal, rags, r
