1.
Pickling
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Pickling is the process of preserving or expanding the lifespan of food by either anaerobic fermentation in brine or immersion in vinegar. The resulting food is called a pickle, or, to prevent ambiguity, the pickling procedure will typically affect the foods texture and flavor. In East Asia, vinaigrette is used as a pickling medium. Foods that are pickled include meats, fruits, eggs, another distinguishing characteristic is a pH of 4.6 or lower, which is sufficient to kill most bacteria. Pickling can preserve perishable foods for months, antimicrobial herbs and spices, such as mustard seed, garlic, cinnamon or cloves, are often added. If the food contains sufficient moisture, a pickling brine may be produced simply by adding dry salt, for example, German sauerkraut and Korean kimchi are produced by salting the vegetables to draw out excess water. Natural fermentation at room temperature, by lactic acid bacteria, produces the required acidity, other pickles are made by placing vegetables in vinegar. Unlike the canning process, pickling does not require that the food be completely sterile before it is sealed, the acidity or salinity of the solution, the temperature of fermentation, and the exclusion of oxygen determine which microorganisms dominate, and determine the flavor of the end product. When both salt concentration and temperature are low, Leuconostoc mesenteroides dominates, producing a mix of acids, alcohol, at higher temperatures Lactobacillus plantarum dominates, which produces primarily lactic acid. Many pickles start with Leuconostoc, and change to Lactobacillus with higher acidity, pickling began 4000 years ago using cucumbers native to India. This was used as a way to food for out-of-season use and for long journeys. Salt pork and salt beef were common staples for sailors before the days of steam engines, although the process was invented to preserve foods, pickles are also made and eaten because people enjoy the resulting flavors. Pickling may also improve the value of food by introducing B vitamins produced by bacteria. The term pickle is derived from the Dutch word pekel, meaning brine, in the U. S. and Canada, and sometimes Australia and New Zealand, the word pickle alone almost always refers to a pickled cucumber, except when it is used figuratively. It may also refer to types of pickles such as pickled onion, pickled cauliflower. In the UK, pickle, as in a cheese and pickle sandwich, may refer to Ploughmans pickle. South Asia has a variety of pickles, which are mainly made from varieties of mango, lemon, lime, goongura, tamarind and Indian gooseberry. Vegetables such as brinjal, carrots, cauliflower, tomato, bitter gourd, green tamarind, ginger, garlic, onion and these fruits and vegetables are generally mixed with ingredients like salt, spices, and vegetable oils and are set to mature in a moistureless medium
2.
Vinegar
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Vinegar is a liquid consisting of about 5–20% acetic acid, water, and other trace chemicals, which may include flavorings. The acetic acid is produced by the fermentation of ethanol by acetic acid bacteria, Vinegar is now mainly used as a cooking ingredient, or in pickling. As the most easily manufactured mild acid, it has historically had a variety of industrial, medical. Commercial vinegar is produced either by a fast or a slow fermentation processes, in general, slow methods are used in traditional vinegars where fermentation proceeds slowly over the course of a few months or up to a year. The longer fermentation period allows for the accumulation of a non-toxic slime composed of acetic acid bacteria, fast methods add mother of vinegar to the source liquid before adding air to oxygenate and promote the fastest fermentation. In fast production processes, vinegar may be produced between 20 hours to three days, the conversion of ethanol and oxygen to acetic acid takes place by the following reaction, CH3CH2OH + O2 → CH3COOH + H2O Vinegar has been made and used by people for thousands of years. Traces of it have been found in Egyptian urns from around 3000 BC, apple cider vinegar is made from cider or apple must, and has a brownish-gold color. It is sometimes sold unfiltered and unpasteurized with the mother of vinegar present and it can be diluted with fruit juice or water or sweetened for consumption. Balsamic vinegar is an aged vinegar produced in the Modena. The original product—Traditional Balsamic Vinegar—is made from the juice, or must. It is very dark brown, rich, sweet, and complex, with the finest grades being aged in casks made variously of oak, mulberry, chestnut, cherry, juniper. Regardless of how it is produced, balsamic vinegar must be made from a grape product, a high acidity level is somewhat hidden by the sweetness of the other ingredients, making it very mellow. It ranges from yellow to golden brown in color, and has a mellow flavor, similar in some respects to rice vinegar. Because it contains no sugar, it is no sweeter than any other vinegar. In the Philippines, it often is labeled as sukang maasim, cane vinegars from Ilocos are made in two different ways. One way is to simply place sugar cane juice in large jars, the other way is through fermentation to produce a local wine known as basi. Low-quality basi is then allowed to undergo acetic acid fermentation that converts alcohol into acetic acid, a white variation has become quite popular in Brazil in recent years, where it is the cheapest type of vinegar sold. It is now common for other types of vinegar to be mixed with cane vinegar to lower the cost
3.
Salt
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Salt is present in vast quantities in seawater, where it is the main mineral constituent. The open ocean has about 35 grams of solids per litre, Salt is essential for life in general, and saltiness is one of the basic human tastes. The tissues of animals contain larger quantities of salt than do plant tissues, Salt is one of the oldest and most ubiquitous food seasonings, and salting is an important method of food preservation. Salt was also prized by the ancient Hebrews, the Greeks, the Romans, the Byzantines, the Hittites, Egyptians, and the Indians. Salt became an important article of trade and was transported by boat across the Mediterranean Sea, along specially built salt roads, the scarcity and universal need for salt has led nations to go to war over it and use it to raise tax revenues. Salt is used in ceremonies and has other cultural significance. Salt is processed from salt mines, or by the evaporation of seawater or mineral-rich spring water in shallow pools. Its major industrial products are caustic soda and chlorine, and is used in industrial processes including the manufacture of polyvinyl chloride, plastics, paper pulp. Of the annual production of around two hundred million tonnes of salt, only about 6% is used for human consumption. Other uses include water conditioning processes, de-icing highways, and agricultural use, edible salt is sold in forms such as sea salt and table salt which usually contains an anti-caking agent and may be iodised to prevent iodine deficiency. As well as its use in cooking and at the table, sodium is an essential nutrient for human health via its role as an electrolyte and osmotic solute. Excessive salt consumption can increase the risk of diseases, such as hypertension, in children. Such health effects of salt have long been studied, accordingly, numerous world health associations and experts in developed countries recommend reducing consumption of popular salty foods. The World Health Organization recommends that adults should consume less than 2,000 mg of sodium, humans have always tended to build communities either around sources of salt, or where they can trade for it. All through history the availability of salt has been pivotal to civilization, the word salary comes from the Latin word for salt because the Roman Legions were sometimes paid in salt. The Natron Valley was a key region that supported the Egyptian Empire to its north, because it supplied it with a kind of salt that came to be called by its name, natron. Even before this, what is now thought to have been the first city in Europe is Solnitsata, in Bulgaria, even the name Solnisata means salt works. A very ancient salt-works operation has been discovered at the Poiana Slatinei archaeological site next to a spring in Lunca, Neamț County
4.
Candy
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Candy, also called sweets or lollies, is a confection that features sugar as a principal ingredient. The category, called sugar confectionery, encompasses any sweet confection, including chocolate, chewing gum, vegetables, fruit, or nuts which have been glazed and coated with sugar are said to be candied. Physically, candy is characterized by the use of a significant amount of sugar or sugar substitutes, unlike a cake or loaf of bread that would be shared among many people, candies are usually made in smaller pieces. However, the definition of candy also depends upon how people treat the food, unlike sweet pastries served for a dessert course at the end of a meal, candies are normally eaten casually, often with the fingers, as a snack between meals. Each culture has its own ideas of what constitutes candy rather than dessert, the same food may be a candy in one culture and a dessert in another. Candy is a food product. Sugar candies include hard candies, soft candies, caramels, marshmallows, taffy, commercially, sugar candies are often divided into groups according to the amount of sugar they contain and their chemical structure. Comparison of sugar candies Chocolate is sometimes treated as a branch of confectionery. In this model, chocolate candies like chocolate candy bars and chocolate truffles are included, hot chocolate or other cocoa-based drinks are excluded, as is candy made from white chocolate. Comparison of chocolate types Candies can be classified into noncrystalline and crystalline types, noncrystalline candies are homogeneous and may be chewy or hard, they include hard candies, caramels, toffees, and nougats. Crystalline candies incorporate small crystals in their structure, are creamy that melt in the mouth or are easily chewed, they include fondant and fudge. Between the 6th and 4th centuries BCE, the Persians, followed by the Greeks, discovered the people in India and they adopted and then spread sugar and sugarcane agriculture. Sugarcane is indigenous to tropical South and Southeast Asia, while the sugar is derived from the Sanskrit word Sharkara. Pieces of sugar were produced by boiling sugarcane juice in ancient India and consumed as Khanda, before sugar was readily available, candy was based on honey. Honey was used in Ancient China, Middle East, Egypt, Greece, Candy is still served in this form today, though now it is more typically seen as a type of garnish. Before the Industrial Revolution, candy was often considered a form of medicine, in the Middle Ages candy appeared on the tables of only the most wealthy at first. At that time, it began as a combination of spices, digestive problems were very common during this time due to the constant consumption of food that was neither fresh nor well balanced. Banquet hosts would typically serve these types of candies at banquets for their guests, one of these candies, sometimes called chamber spice, was made with cloves, ginger, aniseed, juniper berries, almonds and pine kernels dipped in melted sugar
5.
Wine
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Wine is an alcoholic beverage made from fermented grapes. These grapes are generally Vitis vinifera, or a hybrid with Vitis labrusca or Vitis rupestris, grapes are fermented without the addition of sugars, acids, enzymes, water, or other nutrients. Yeast consumes the sugar in the grapes and converts it to ethanol, different varieties of grapes and strains of yeasts produce different styles of wine. These variations result from the interactions between the biochemical development of the grape, the reactions involved in fermentation, the terroir. Many countries enact legal appellations intended to define styles and qualities of wine and these typically restrict the geographical origin and permitted varieties of grapes, as well as other aspects of wine production. There are also made from fermenting other fruits or cereals. Wines made from other than grapes include rice wine and various fruit wines such as those made from plums or cherries. Some well known examples are hard cider from apples, perry from pears, pomegranate wine, Wine has been produced for thousands of years. The earliest known traces of wine from Georgia in Eurasia where 8000-year-old wine jars were found and in Iran with 7, the earliest known winery is the 6, 100-year-old Areni-1 winery Armenia. Wine reached the Balkans by 4500 BC and was consumed and celebrated in ancient Greece, Thrace, throughout history, wine has been consumed for its intoxicating effects, which are evident after the normal serving size of five ounces. Wine has long played an important role in religion, the earliest chemically attested grape wine was discovered at Hajji Firuz in the northwestern Zagros Mountains dating back to 5400 BC. The earliest evidence of a fermented drink was found in Georgia, where wine residue inside ceramic jars dates from 6000 BC. The earliest evidence of a production facility is the Areni-1 winery in Armenia and is at least 6100 years old, presumably. A2003 report by archaeologists indicates a possibility that grapes were mixed with rice to produce mixed fermented beverages in China in the years of the seventh millennium BC. Pottery jars from the Neolithic site of Jiahu, Henan, contained traces of tartaric acid, however, other fruits indigenous to the region, such as hawthorn, cannot be ruled out. The spread of wine culture westwards was most probably due to the Phoenicians who spread outward from a base of city-states along the Lebanese, Syrian, the wines of Byblos were exported to Egypt during the Old Kingdom and then throughout the Mediterranean. Evidence includes two Phoenician shipwrecks from 750 BC discovered by Robert Ballard, whose cargo of wine was still intact. As the first great traders in wine, the Phoenicians seem to have protected it from oxidation with a layer of oil, followed by a seal of pinewood and resin
6.
Food packaging
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Food packaging is packaging for food. A package provides protection, tampering resistance, and special physical, chemical and it may bear a nutrition facts label and other information about food being offered for sale. Barrier protection - A barrier from oxygen, water vapor, dust, permeation is a critical factor in design. Some packages contain desiccants or oxygen absorbers to help extend shelf life, modified atmospheres or controlled atmospheres are also maintained in some food packages. Keeping the contents clean, fresh, and safe for the shelf life is a primary function. Containment or agglomeration - Small items are grouped together in one package to allow efficient handling. Liquids, powders, and granular materials need containment, information transmission - Packages and labels communicate how to use, transport, recycle, or dispose of the package or product. Some types of information are required by governments, marketing - The packaging and labels can be used by marketers to encourage potential buyers to purchase the product. Package design has been an important and constantly evolving phenomenon for several decades, marketing communications and graphic design are applied to the surface of the package and the point of sale display. Security - Packaging can play an important role in reducing the security risks of shipment, Packages can be made with improved tamper resistance to deter tampering and also can have tamper-evident features to help indicate tampering. Packages can be engineered to reduce the risks of package pilferage, some package constructions are more resistant to pilferage. Packages may include authentication seals to indicate that the package. Using packaging in this way is a means of retail loss prevention, convenience - Packages can have features which add convenience in distribution, handling, stacking, display, sale, opening, reclosing, use, and reuse. Portion control - Single-serving packaging has an amount of contents to control usage. Bulk commodities can be divided into packages that are a suitable size for individual households. It also aids the control of inventory, selling sealed one-liter bottles of milk, the above materials are fashioned into different types of food packages and containers such as, Primary packaging is the main package that holds the food that is being processed. Secondary packaging combines the primary packages into one box being made, tertiary packaging combines all of the secondary packages into one pallet. Packaging machines may be of the general types, Reduced packaging
7.
Europe
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Europe is a continent that comprises the westernmost part of Eurasia. Europe is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, yet the non-oceanic borders of Europe—a concept dating back to classical antiquity—are arbitrary. Europe covers about 10,180,000 square kilometres, or 2% of the Earths surface, politically, Europe is divided into about fifty sovereign states of which the Russian Federation is the largest and most populous, spanning 39% of the continent and comprising 15% of its population. Europe had a population of about 740 million as of 2015. Further from the sea, seasonal differences are more noticeable than close to the coast, Europe, in particular ancient Greece, was the birthplace of Western civilization. The fall of the Western Roman Empire, during the period, marked the end of ancient history. Renaissance humanism, exploration, art, and science led to the modern era, from the Age of Discovery onwards, Europe played a predominant role in global affairs. Between the 16th and 20th centuries, European powers controlled at times the Americas, most of Africa, Oceania. The Industrial Revolution, which began in Great Britain at the end of the 18th century, gave rise to economic, cultural, and social change in Western Europe. During the Cold War, Europe was divided along the Iron Curtain between NATO in the west and the Warsaw Pact in the east, until the revolutions of 1989 and fall of the Berlin Wall. In 1955, the Council of Europe was formed following a speech by Sir Winston Churchill and it includes all states except for Belarus, Kazakhstan and Vatican City. Further European integration by some states led to the formation of the European Union, the EU originated in Western Europe but has been expanding eastward since the fall of the Soviet Union in 1991. The European Anthem is Ode to Joy and states celebrate peace, in classical Greek mythology, Europa is the name of either a Phoenician princess or of a queen of Crete. The name contains the elements εὐρύς, wide, broad and ὤψ eye, broad has been an epithet of Earth herself in the reconstructed Proto-Indo-European religion and the poetry devoted to it. For the second part also the divine attributes of grey-eyed Athena or ox-eyed Hera. The same naming motive according to cartographic convention appears in Greek Ανατολή, Martin Litchfield West stated that phonologically, the match between Europas name and any form of the Semitic word is very poor. Next to these there is also a Proto-Indo-European root *h1regʷos, meaning darkness. Most major world languages use words derived from Eurṓpē or Europa to refer to the continent, in some Turkic languages the originally Persian name Frangistan is used casually in referring to much of Europe, besides official names such as Avrupa or Evropa
8.
Australia
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Australia, officially the Commonwealth of Australia, is a country comprising the mainland of the Australian continent, the island of Tasmania and numerous smaller islands. It is the worlds sixth-largest country by total area, the neighbouring countries are Papua New Guinea, Indonesia and East Timor to the north, the Solomon Islands and Vanuatu to the north-east, and New Zealand to the south-east. Australias capital is Canberra, and its largest urban area is Sydney, for about 50,000 years before the first British settlement in the late 18th century, Australia was inhabited by indigenous Australians, who spoke languages classifiable into roughly 250 groups. The population grew steadily in subsequent decades, and by the 1850s most of the continent had been explored, on 1 January 1901, the six colonies federated, forming the Commonwealth of Australia. Australia has since maintained a liberal democratic political system that functions as a federal parliamentary constitutional monarchy comprising six states. The population of 24 million is highly urbanised and heavily concentrated on the eastern seaboard, Australia has the worlds 13th-largest economy and ninth-highest per capita income. With the second-highest human development index globally, the country highly in quality of life, health, education, economic freedom. The name Australia is derived from the Latin Terra Australis a name used for putative lands in the southern hemisphere since ancient times, the Dutch adjectival form Australische was used in a Dutch book in Batavia in 1638, to refer to the newly discovered lands to the south. On 12 December 1817, Macquarie recommended to the Colonial Office that it be formally adopted, in 1824, the Admiralty agreed that the continent should be known officially as Australia. The first official published use of the term Australia came with the 1830 publication of The Australia Directory and these first inhabitants may have been ancestors of modern Indigenous Australians. The Torres Strait Islanders, ethnically Melanesian, were originally horticulturists, the northern coasts and waters of Australia were visited sporadically by fishermen from Maritime Southeast Asia. The first recorded European sighting of the Australian mainland, and the first recorded European landfall on the Australian continent, are attributed to the Dutch. The first ship and crew to chart the Australian coast and meet with Aboriginal people was the Duyfken captained by Dutch navigator, Willem Janszoon. He sighted the coast of Cape York Peninsula in early 1606, the Dutch charted the whole of the western and northern coastlines and named the island continent New Holland during the 17th century, but made no attempt at settlement. William Dampier, an English explorer and privateer, landed on the north-west coast of New Holland in 1688, in 1770, James Cook sailed along and mapped the east coast, which he named New South Wales and claimed for Great Britain. The first settlement led to the foundation of Sydney, and the exploration, a British settlement was established in Van Diemens Land, now known as Tasmania, in 1803, and it became a separate colony in 1825. The United Kingdom formally claimed the part of Western Australia in 1828. Separate colonies were carved from parts of New South Wales, South Australia in 1836, Victoria in 1851, the Northern Territory was founded in 1911 when it was excised from South Australia
9.
New Zealand
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New Zealand /njuːˈziːlənd/ is an island nation in the southwestern Pacific Ocean. The country geographically comprises two main landmasses—the North Island, or Te Ika-a-Māui, and the South Island, or Te Waipounamu—and around 600 smaller islands. New Zealand is situated some 1,500 kilometres east of Australia across the Tasman Sea and roughly 1,000 kilometres south of the Pacific island areas of New Caledonia, Fiji, because of its remoteness, it was one of the last lands to be settled by humans. During its long period of isolation, New Zealand developed a distinct biodiversity of animal, fungal, the countrys varied topography and its sharp mountain peaks, such as the Southern Alps, owe much to the tectonic uplift of land and volcanic eruptions. New Zealands capital city is Wellington, while its most populous city is Auckland, sometime between 1250 and 1300 CE, Polynesians settled in the islands that later were named New Zealand and developed a distinctive Māori culture. In 1642, Dutch explorer Abel Tasman became the first European to sight New Zealand, in 1840, representatives of Britain and Māori chiefs signed the Treaty of Waitangi, which declared British sovereignty over the islands. In 1841, New Zealand became a colony within the British Empire, today, the majority of New Zealands population of 4.7 million is of European descent, the indigenous Māori are the largest minority, followed by Asians and Pacific Islanders. Reflecting this, New Zealands culture is derived from Māori and early British settlers. The official languages are English, Māori and New Zealand Sign Language, New Zealand is a developed country and ranks highly in international comparisons of national performance, such as health, education, economic freedom and quality of life. Since the 1980s, New Zealand has transformed from an agrarian, Queen Elizabeth II is the countrys head of state and is represented by a governor-general. In addition, New Zealand is organised into 11 regional councils and 67 territorial authorities for local government purposes, the Realm of New Zealand also includes Tokelau, the Cook Islands and Niue, and the Ross Dependency, which is New Zealands territorial claim in Antarctica. New Zealand is a member of the United Nations, Commonwealth of Nations, ANZUS, Organisation for Economic Co-operation and Development, Pacific Islands Forum, and Asia-Pacific Economic Cooperation. Dutch explorer Abel Tasman sighted New Zealand in 1642 and called it Staten Landt, in 1645, Dutch cartographers renamed the land Nova Zeelandia after the Dutch province of Zeeland. British explorer James Cook subsequently anglicised the name to New Zealand, Aotearoa is the current Māori name for New Zealand. It is unknown whether Māori had a name for the country before the arrival of Europeans. Māori had several names for the two main islands, including Te Ika-a-Māui for the North Island and Te Waipounamu or Te Waka o Aoraki for the South Island. Early European maps labelled the islands North, Middle and South, in 1830, maps began to use North and South to distinguish the two largest islands and by 1907, this was the accepted norm. The New Zealand Geographic Board discovered in 2009 that the names of the North Island and South Island had never been formalised and this set the names as North Island or Te Ika-a-Māui, and South Island or Te Waipounamu
10.
Food and Drug Administration
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The Food and Drug Administration is a federal agency of the United States Department of Health and Human Services, one of the United States federal executive departments. As of 2017, 3/4th of the FDA budget is funded by the pharmaceutical companies due to the Prescription drug user fee act and these include regulating lasers, cellular phones, condoms and control of disease on products ranging from certain household pets to sperm donation for assisted reproduction. The FDA is led by the Commissioner of Food and Drugs, appointed by the President with the advice, the Commissioner reports to the Secretary of Health and Human Services. Dr. Robert M. Califf, MD is the current commissioner, who took over in February 2016 for Dr. Stephen Ostroff, the FDA has its headquarters in unincorporated White Oak, Maryland. The agency also has 223 field offices and 13 laboratories located throughout the 50 states, the United States Virgin Islands, in 2008, the FDA began to post employees to foreign countries, including China, India, Costa Rica, Chile, Belgium, and the United Kingdom. The site was renamed from the White Oak Naval Surface Warfare Center to the Federal Research Center at White Oak, the first building, the Life Sciences Laboratory, was dedicated and opened with 104 employees on the campus in December 2003. Only one original building from the facility was kept. All other buildings are new construction, the project is slated to be completed by 2017, assuming future Congressional funding While most of the Centers are located in the Washington, D. C. The Office of Regulatory Affairs is considered the eyes and ears of the agency, the Office of Regulatory Affairs is divided into five regions, which are further divided into 20 districts. Districts are based roughly on the divisions of the federal court system. Each district comprises a main office and a number of Resident Posts. ORA also includes the Agencys network of laboratories, which analyze any physical samples taken. Though samples are usually food-related, some laboratories are equipped to analyze drugs, cosmetics, the Office of Criminal Investigations was established in 1991 to investigate criminal cases. Unlike ORA Investigators, OCI Special Agents are armed, and dont focus on aspects of the regulated industries. In many cases, OCI pursues cases involving Title 18 violations, OCI Special Agents often come from other criminal investigations backgrounds, and work closely with the Federal Bureau of Investigation, Assistant Attorney General, and even Interpol. OCI receives cases from a variety of sources—including ORA, local agencies, OCI is a smaller branch, comprising about 200 agents nationwide. The FDA frequently works with federal agencies, including the Department of Agriculture, Drug Enforcement Administration, Customs and Border Protection. Often local and state government agencies also work with the FDA to provide regulatory inspections, the FDA regulates more than US$1 trillion worth of consumer goods, about 25% of consumer expenditures in the United States
11.
PH
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In chemistry, pH is a numeric scale used to specify the acidity or basicity of an aqueous solution. It is approximately the negative of the base 10 logarithm of the concentration, measured in units of moles per liter. More precisely it is the negative of the logarithm to base 10 of the activity of the hydrogen ion, solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic. Pure water is neutral, at pH7, being neither an acid nor a base, contrary to popular belief, the pH value can be less than 0 or greater than 14 for very strong acids and bases respectively. The pH scale is traceable to a set of standard solutions whose pH is established by international agreement, the pH of aqueous solutions can be measured with a glass electrode and a pH meter, or an indicator. In the first papers, the notation had the H as a subscript to the p, as so. The exact meaning of the p in pH is disputed, but according to the Carlsberg Foundation and it has also been suggested that the p stands for the German Potenz, others refer to French puissance. Another suggestion is that the p stands for the Latin terms pondus hydrogenii, potentia hydrogenii and it is also suggested that Sørensen used the letters p and q simply to label the test solution and the reference solution. Currently in chemistry, the p stands for decimal cologarithm of, PH is defined as the decimal logarithm of the reciprocal of the hydrogen ion activity, aH+, in a solution. P H = − log 10 = log 10 For example and this definition was adopted because ion-selective electrodes, which are used to measure pH, respond to activity. For H+ number of electrons transferred is one and it follows that electrode potential is proportional to pH when pH is defined in terms of activity. The reference electrode may be a silver chloride electrode or a calomel electrode, the hydrogen-ion selective electrode is a standard hydrogen electrode. Reference electrode | concentrated solution of KCl || test solution | H2 | Pt Firstly, the cell is filled with a solution of hydrogen ion activity. Then the emf, EX, of the cell containing the solution of unknown pH is measured. PH = pH + E S − E X z The difference between the two measured emf values is proportional to pH and this method of calibration avoids the need to know the standard electrode potential. The proportionality constant, 1/z is ideally equal to 12.303 R T / F the Nernstian slope, to apply this process in practice, a glass electrode is used rather than the cumbersome hydrogen electrode. A combined glass electrode has a reference electrode. It is calibrated against buffer solutions of hydrogen ion activity
12.
Oxygen
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Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the group on the periodic table and is a highly reactive nonmetal. By mass, oxygen is the third-most abundant element in the universe, after hydrogen, at standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula O2. This is an important part of the atmosphere and diatomic oxygen gas constitutes 20. 8% of the Earths atmosphere, additionally, as oxides the element makes up almost half of the Earths crust. Most of the mass of living organisms is oxygen as a component of water, conversely, oxygen is continuously replenished by photosynthesis, which uses the energy of sunlight to produce oxygen from water and carbon dioxide. Oxygen is too reactive to remain a free element in air without being continuously replenished by the photosynthetic action of living organisms. Another form of oxygen, ozone, strongly absorbs ultraviolet UVB radiation, but ozone is a pollutant near the surface where it is a by-product of smog. At low earth orbit altitudes, sufficient atomic oxygen is present to cause corrosion of spacecraft, the name oxygen was coined in 1777 by Antoine Lavoisier, whose experiments with oxygen helped to discredit the then-popular phlogiston theory of combustion and corrosion. One of the first known experiments on the relationship between combustion and air was conducted by the 2nd century BCE Greek writer on mechanics, Philo of Byzantium. In his work Pneumatica, Philo observed that inverting a vessel over a burning candle, Philo incorrectly surmised that parts of the air in the vessel were converted into the classical element fire and thus were able to escape through pores in the glass. Many centuries later Leonardo da Vinci built on Philos work by observing that a portion of air is consumed during combustion and respiration, Oxygen was discovered by the Polish alchemist Sendivogius, who considered it the philosophers stone. In the late 17th century, Robert Boyle proved that air is necessary for combustion, English chemist John Mayow refined this work by showing that fire requires only a part of air that he called spiritus nitroaereus. From this he surmised that nitroaereus is consumed in both respiration and combustion, Mayow observed that antimony increased in weight when heated, and inferred that the nitroaereus must have combined with it. Accounts of these and other experiments and ideas were published in 1668 in his work Tractatus duo in the tract De respiratione. Robert Hooke, Ole Borch, Mikhail Lomonosov, and Pierre Bayen all produced oxygen in experiments in the 17th and the 18th century but none of them recognized it as a chemical element. This may have been in part due to the prevalence of the philosophy of combustion and corrosion called the phlogiston theory, which was then the favored explanation of those processes. Established in 1667 by the German alchemist J. J. Becher, one part, called phlogiston, was given off when the substance containing it was burned, while the dephlogisticated part was thought to be its true form, or calx. The fact that a substance like wood gains overall weight in burning was hidden by the buoyancy of the combustion products
