ব্যবহারকারী:SMA/WORKSHOP

নুন, যা টেবিল লবণের হিসাবেও পরিচিত বা এর রাসায়নিক সূত্র ন্যাকএল দ্বারা ব্যবহৃত হয়, এটি সোডিয়াম এবং ক্লোরাইড আয়ন দ্বারা তৈরি একটি আয়নিক যৌগ। সমস্ত জীবন বেঁচে থাকার জন্য তার রাসায়নিক বৈশিষ্ট্যের উপর নির্ভর করে বিকশিত হয়েছে। এটি খাদ্য সংরক্ষণ থেকে শুরু করে সিজনিং পর্যন্ত হাজার বছর ধরে মানুষ ব্যবহার করে আসছে। খাদ্য সংরক্ষণের জন্য লবণের সক্ষমতা সভ্যতার বিকাশে একটি প্রাথমিক অবদানকারী ছিল। এটি খাবারের মৌসুমী প্রাপ্যতার উপর নির্ভরতা দূরীকরণে সহায়তা করেছিল এবং বড় দূরত্বের মাধ্যমে খাদ্য পরিবহন সম্ভব করেছে। যাইহোক, লবণ পাওয়া প্রায়শই কঠিন ছিল, সুতরাং এটি একটি অত্যন্ত মূল্যবান বাণিজ্য আইটেম ছিল এবং নির্দিষ্ট লোকেরা মুদ্রার এক রূপ হিসাবে বিবেচিত হত। ইতালির সালারিয়া হয়ে অনেকগুলি নুনের রাস্তা ব্রোঞ্জ যুগ দ্বারা প্রতিষ্ঠিত হয়েছিল।

ইতিহাসের সবকালেই, লবণের সহজলভ্যতা সভ্যতার কাছে গুরুত্বপূর্ণ। ব্রিটেনে, স্থানের নামের সাথে "-উইচ" প্রত্যয়টির অর্থ এটি একবার স্যান্ডউইচ এবং নরউইচের মতো লবণের উত্স ছিল। নাট্রন উপত্যকা একটি মূল অঞ্চল ছিল যা এর উত্তরে মিশরীয় সাম্রাজ্যকে সমর্থন করেছিল, কারণ এটি এটিকে এক ধরণের নুন সরবরাহ করেছিল যা এর নাম ন্যাট্রন নামে ডাকা হয়েছিল। আজ, লবণ প্রায় সর্বজনীন অ্যাক্সেসযোগ্য, তুলনামূলকভাবে সস্তা এবং প্রায়শই আয়োডিনযুক্ত।

Collected salt mounds

Naturally formed salt crystals

Ancient method of boiling brine into pure salt in China

Salt, also referred to as table salt or by its chemical formula NaCl, is an ionic compound made of sodium and chloride ions. All life has evolved to depend on its chemical properties to survive. It has been used by humans for thousands of years, from food preservation to seasoning. Salt's ability to preserve food was a founding contributor to the development of civilization. It helped to eliminate dependence on seasonal availability of food, and made it possible to transport food over large distances. However, salt was often difficult to obtain, so it was a highly valued trade item, and was considered a form of currency by certain peoples. Many salt roads, such as the via Salaria in Italy, had been established by the Bronze Age.

All through history, availability of salt has been pivotal to civilization. In Britain, the suffix "-wich" in a placename means it was once a source of salt, as in Sandwich and Norwich. 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. Today, salt is almost universally accessible, relatively cheap, and often iodized.

Sources

Salt comes from two main sources: sea water and the sodium chloride mineral halite (also known as rock salt). Rock salt occurs in vast beds of sedimentary evaporite minerals that result from the drying up of enclosed lakes, playas, and seas. Salt beds may be up to 350 m thick and underlie broad areas. In the United States and Canada extensive underground beds extend from the Appalachian basin of western New York through parts of Ontario and under much of the Michigan basin. Other deposits are in Texas, Ohio, Kansas, New Mexico, Nova Scotia, and Saskatchewan. In the United Kingdom underground beds are found in Cheshire and around Droitwich. Salzburg, Austria, was named "the city of salt" for its mines. High-quality rock salt was cut in medieval Transylvania, Maramureş and Southern Poland (Wieliczka). Tuzla in Bosnia and Herzegovina was named in Hungarian Só (salt) from the twelfth century on and later "place of salt" by Turks.

Salt is extracted from underground beds either by mining or by solution mining using water to dissolve the salt. In solution mining the salt reaches the surface as brine, from which the water is evaporated leaving salt crystals.

History

The Sečovlje Saltworks on the Northern Adriatic Sea were probably started in Antiquity and were first mentioned in 804 in the document on Placitum of Riziano.

Ancient world

Solnitsata, the earliest known town in Europe, was built around a salt production facility. Located in present-day Bulgaria, the town is thought by archaeologists to have accumulated wealth by supplying salt throughout the Balkans.

Salt was of high value to the Jews, Greeks, Tamils, Chinese, Hittites and other peoples of antiquity. Aside from being a contributing factor in the development of civilization, salt was also used in the military practice of salting the earth by various peoples, beginning with the Assyrians. In the early years of the Roman Republic, with the growth of the city of Rome, roads were built to make transportation of salt to the capital city easier. An example was the Via Salaria (originally a Sabine trail), leading from Rome to the Adriatic Sea. The Adriatic, having a higher salinity due to its shallow depth, had more productive solar ponds compared with those of the Tyrrhenian Sea, much closer to Rome. The word "salary" comes from the Latin word for salt. A persistent modern claim that the Roman Legions were sometimes paid in salt is baseless; the word salary ultimately derives from an allowance—salārium—paid to Roman soldiers for the purchase of salt.

Vertical derricks and drilling rig from Qing dynasty Zigong, China extracting brine from deep underground wells.

During the late Roman Empire and throughout the Middle Ages salt was a precious commodity carried along the salt roads into the heartland of the Germanic tribes. Caravans consisting of as many as forty thousand camels traversed four hundred miles of the Sahara bearing salt to inland markets in the Sahel, sometimes trading salt for slaves: Timbuktu was a noted salt and slave market.

Salt in Chinese history was both a driver of technological development and a stable source of revenue for the imperial government.

Cities and wars

Salt production on Læsø, Denmark (reconstruction)

Salt has played a prominent role in determining the power and location of the world's great cities. Liverpool rose from just a small English port to become the prime exporting port for the salt dug in the great Cheshire salt mines and thus became the entrepôt for much of the world's salt in the 19th century.

Salt created and destroyed empires. The salt mines of Poland led to a vast kingdom in the 16th century, only to be demolished when Germans brought in sea salt (which most of the world considered superior to rock salt). Venice fought and won a war with Genoa over spices. However, Genoese Christopher Columbus and Giovanni Caboto would later destroy the Mediterranean trade by introducing the New World to the market.

Cities, states and duchies along the salt roads exacted heavy duties and taxes for the salt passing through their territories. This practice even caused the formation of cities, such as the city of Munich in 1158, when the then Duke of Bavaria, Henry the Lion, decided that the bishops of Freising no longer needed their salt revenue.

The gabelle—a hated French salt tax—was enacted in 1286 and maintained until 1790. Because of the gabelles, common salt was of such a high value that it caused mass population shifts and exodus, attracted invaders and caused wars.

In American history, salt has been a major factor in outcomes of wars. In the Revolutionary War, the British used Loyalists to intercept Revolutionaries' salt shipments and interfere with their ability to preserve food. During the War of 1812, salt brine was used to pay soldiers in the field, as the government was too poor to pay them with money. Before Lewis and Clark set out for the Louisiana Territory, President Jefferson in his address to Congress mentioned a mountain of salt, 180 miles long and 45 wide, supposed to lie near the Missouri River, which would have been of inconceivable value, as a reason for their expedition.

During India's independence movement, Mohandas Gandhi organized the Salt Satyagraha protest to demonstrate against the British salt tax.

Salt production in England

Salt was produced from both mines and sea in Medieval England. The open-pan salt making method was used along the Lincolnshire coast and in the saltmarshes of Bitterne Manor on the banks of the River Itchen in Hampshire where salt production was a notable industry.

আরও দেখুন: -wich town

আরও দেখুন: History of salt in Middlewich

Wich and wych are names associated (but not exclusively) with brine springs or wells in England. Originally derived from the Latin vicus, meaning "place", by the 11th century use of the 'wich' suffix in placenames was associated with places with a specialised function including that of salt production. Several English places carry the suffix and are historically related to salt, including the four Cheshire 'wiches' of Middlewich, Nantwich, Northwich and Leftwich (a small village south of Northwich), and Droitwich in Worcestershire. Middlewich, Nantwich, Northwich and Droitwich are known as the "Domesday Wiches" due to their mention in the Domesday Book, "an indication of the significance of the salt-working towns in the economy of the region, and indeed of the country". Salt was very important to Europe because it was hard to trade with Africa and they needed to produce it themselves.

Salt trade

Monopolies over salt production and trade were essential aspects of government revenue in imperial China and retained its significance until 20th century.

During modern times, it became more profitable to sell salted food than pure salt. Thus sources of food to salt went hand in hand with salt making. The British controlled saltworks in the Bahamas as well as North American cod fisheries. The search for oil in the late 19th and early 20th centuries used the technology and methods pioneered by salt miners, even to the degree that they looked for oil where salt domes were located.

Salt production

A 'zouthuisje', i.e. little salt-house, used for salt making today. Many of these structures can be found near Twekkelo in Twente, the Netherlands.

On an industrial scale, salt is produced in one of two principal ways: the evaporation of salt water (brine) or by mining. Evaporation can either be solar evaporation or using some heating device.

Solar evaporation of seawater

In the correct climate (one for which the ratio of evaporation to rainfall is suitably high) it is possible to use solar evaporation of sea water to produce salt. Brine is evaporated in a linked set of ponds until the solution is sufficiently concentrated by the final pond so that the salt crystallizes on the pond's floor.

Open pan production from brine

মূল নিবন্ধ: Open pan salt making

One of the traditional methods of salt production in more temperate climates is using open pans. In open-pan production, salt brine is heated in large, shallow open pans. The earliest examples of this date back to prehistoric times and the pans were made of either a type of ceramic called briquetage, or lead. Later examples were made from iron. This change coincided with a change from wood to coal for the purpose of heating the brine. Brine would be pumped into the pans and concentrated by the heat of the fire burning underneath. As crystals of salt formed, these would be raked out and more brine added.

Closed pan production under vacuum

The open pan salt works has effectively been replaced with a closed pan system where the brine solution is evaporated under a partial vacuum.

Salt mines

In the second half of the 19th century, industrial mining and new drilling techniques made the discovery of more and deeper deposits possible, increasing mine salt's share of the market. Although mining salt was generally more expensive than extracting it from brine via solar evaporation of seawater, the introduction of this new source reduced the price of salt due to a reduction of monopolization. Extraction of salt from brine is still heavily used; for example, vacuum salt produced by British Salt in Middlewich has 57% of the UK market for salt used in cooking.

Other salt uses

মূল নিবন্ধ: Bath salts

The earliest systematic exposition of the different kinds of salts, its uses, and the methods of its extraction was published in China around 2700 BCE. Hippocrates encouraged his fellow healers to use salt water to heal various ailments by immersing their patients in sea water. The ancient Greeks continued this, and in 1753, English author and physician Richard Russell published The Uses of Sea Water in which he declared that salt was a "common defence against the corruption of…bodies" and "contribut[es] greatly to all cures".

See also

• Alberger process
• Bath salts
• Cerro de la Sal (Salt Mountain), Peru
• Fish sauce
• Garum
• Illinois Salines
• International Salt Co. v. United States
• Iodised salt
• James Ford (pirate)
• Joy Morton
• John Crenshaw
• Lüneburg Saltworks
• Mineral lick (salt lick)
• Morton Salt
• Red hill (salt making)
• Saltern
• Salt evaporation pond
• Salt in Cheshire
• Salt industry in Ghana
• Salt in the American Civil War
• Salt March (India)
• Salt Riot (Moscow uprising of 1648)
• Seawater greenhouse
• Anikey Stroganov (Solvychegodsk and Perm salterns)
• Sülze Saltworks

Further reading

• ওয়েব্যাক মেশিনে Salt Institute History of Salt (মার্চ ৩, ২০০৯ তারিখে আর্কাইভকৃত)
• The Role of Salt in Eastern North American Prehistory

Description

Cyathia of Euphorbia baylissii

Croton cultivar 'Petra'.

The leaves are alternate, seldom opposite, with stipules. They are mainly simple, but where compound, are always palmate, never pinnate. Stipules may be reduced to hairs, glands, or spines, or in succulent species are sometimes absent.

The plants can be monoecious or dioecious. The radially symmetrical flowers are unisexual, with the male and female flowers usually on the same plant. As can be expected from such a large family, a wide variety exists in the structure of the flowers. The stamens (the male organs) number from one to 10 (or even more). The female flowers are hypogynous, that is, with superior ovaries.

The genera in tribe Euphorbieae, subtribe Euphorbiinae (Euphorbia and close relatives) show a highly specialized form of pseudanthium ("false flower" made up of several true flowers) called a cyathium. This is usually a small, cup-like involucre consisting of fused-together bracts and peripheral nectary glands, surrounding a ring of male flowers, each a single stamen. In the middle of the cyathium stands a female flower: a single pistil with branched stigmas. This whole arrangement resembles a single flower.

The fruit is usually a schizocarp, but sometimes a drupe. A typical schizocarp is the regma, a capsular fruit with three or more cells, each of which splits open explosively at maturity, scattering the small seeds.

The family contains a large variety of phytotoxins (toxic substances produced by plants), including diterpene esters, alkaloids and cyanogenic glycosides (e.g. root tubers of cassava). The seeds of the castor oil plant Ricinus communis contain the highly toxic carbohydrate-binding protein ricin.

A milky latex is a characteristic of the subfamilies Euphorbioideae and Crotonoideae, and the latex of the rubber tree Hevea brasiliensis is the primary source of natural rubber. The latex is poisonous in the Euphorbioideae, but innocuous in the Crotonoideae. White mangrove, also known as blind-your-eye mangrove latex (Excoecaria agallocha), causes blistering on contact and temporary blindness if it contacts the eyes. Other common names are milky mangrove, buta buta (Malay), and gewa (Bangladesh). The latex of spurge was used as a laxative.

Recent molecular studies have shown that the enigmatic family Rafflesiaceae, which was only recently recognized to belong to order Malpighiales, is derived from within the Euphorbiaceae.

Taxonomy

মূল নিবন্ধ: List of Euphorbiaceae genera

The Euphorbiaceae family is the fifth largest flowering plant family and has about 7,500 species organised into 300 genera, 37 tribes, and three subfamilies.

Uses

Some spurge plants have economic significance, such as cassava (Manihot esculenta), castor oil plant (Ricinus communis), Barbados nut (Jatropha curcas), and the Para rubber tree (Hevea brasiliensis). Many are grown as ornamental plants, such as poinsettia (Euphorbia pulcherrima). Leafy spurge (Euphorbia esula) and Chinese tallow (Triadica sebifera) are invasive weeds in North America.

Although some species of Euphorbiaceae have been used in traditional medicine, as of 2019, there is no rigorous clinical evidence that euphorbia extracts are effective for treating any disease. Numerous Euphorbiaceae species are listed on the poisonous plant database of the US Food and Drug Administration.

Phytochemistry

Phytochemicals found in Euphorbiaceae species include diterpenoids, terpenoids, flavonoids, alkaloids, tannins, neriifolins, cycloartenol, lectin, and taraxerol, among others.

Vulnerability

Some species, despite their medicinal benefits, are facing the risk of becoming extinct. These include the Euphorbia species E. appariciana, E. attastoma, E. crossadenia, and E. gymnoclada.

External links

• Marc Altenloh collection (photos).
• International Euphorbia Society
• Cactus and Succulent Society of America
• Data from GRIN Taxonomy
• Euphorbiaceae in L. Watson and M.J. Dallwitz (1992 onwards). The families of flowering plants: descriptions, illustrations, identification, information retrieval. https://web.archive.org/web/20070103200438/http://delta-intkey.com/