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71-461: The sands formed from the decomposition of volcanic rock ( basalt ) gullies into clay , further transformed into ferralitic soil by total hydrolysis ; the two main elements of the resulting soil, iron and aluminium , are responsible for red/anthracite and blue/purplish colours respectively. The different shades of colour are believed to be a consequence of the molten volcanic rock cooling down at different external temperatures (hence rates), but

142-471: A flame test , sodium and its compounds glow yellow because the excited 3s electrons of sodium emit a photon when they fall from 3p to 3s; the wavelength of this photon corresponds to the D line at about 589.3 nm. Spin-orbit interactions involving the electron in the 3p orbital split the D line into two, at 589.0 and 589.6 nm; hyperfine structures involving both orbitals cause many more lines. Twenty isotopes of sodium are known, but only Na

213-423: A phase-transfer catalyst . Sodium content of samples is determined by atomic absorption spectrophotometry or by potentiometry using ion-selective electrodes. Like the other alkali metals, sodium dissolves in ammonia and some amines to give deeply colored solutions; evaporation of these solutions leaves a shiny film of metallic sodium. The solutions contain the coordination complex [Na(NH 3 ) 6 ] , with

284-503: A raising agent , and sodablasting . Along with potassium, many important medicines have sodium added to improve their bioavailability ; though potassium is the better ion in most cases, sodium is chosen for its lower price and atomic weight. Sodium hydride is used as a base for various reactions (such as the aldol reaction ) in organic chemistry. Metallic sodium is used mainly for the production of sodium borohydride , sodium azide , indigo , and triphenylphosphine . A once-common use

355-457: A vesicular texture caused by voids left by volatiles trapped in the molten lava . Pumice is a highly vesicular rock produced in explosive volcanic eruptions . Most modern petrologists classify igneous rocks, including volcanic rocks, by their chemistry when dealing with their origin. The fact that different mineralogies and textures may be developed from the same initial magmas has led petrologists to rely heavily on chemistry to look at

426-430: A black glassy substance called obsidian . When filled with bubbles of gas, the same lava may form the spongy appearing pumice . Allowed to cool slowly, it forms a light-colored, uniformly solid rock called rhyolite. The lavas, having cooled rapidly in contact with the air or water, are mostly finely crystalline or have at least fine-grained ground-mass representing that part of the viscous semi-crystalline lava flow that

497-410: A close analogy to hot solutions of salts in water, which, when they approach the saturation temperature, first deposit a crop of large, well-formed crystals (labile stage) and subsequently precipitate clouds of smaller less perfect crystalline particles (metastable stage). In igneous rocks the first generation of crystals generally forms before the lava has emerged to the surface, that is to say, during

568-525: A compound of sodium with the Latin name of sodanum was used as a headache remedy. The name sodium is thought to originate from the Arabic suda , meaning headache, as the headache-alleviating properties of sodium carbonate or soda were well known in early times. Although sodium, sometimes called soda , had long been recognized in compounds, the metal itself was not isolated until 1807 by Sir Humphry Davy through

639-524: A corner of our 60 m room farthest away from the apparatus, we exploded 3 mg of sodium chlorate with milk sugar while observing the nonluminous flame before the slit. After a while, it glowed a bright yellow and showed a strong sodium line that disappeared only after 10 minutes. From the weight of the sodium salt and the volume of air in the room, we easily calculate that one part by weight of air could not contain more than 1/20 millionth weight of sodium. The Earth's crust contains 2.27% sodium, making it

710-459: A good supplier will know what sort of volcanic rock they are selling. The sub-family of rocks that form from volcanic lava are called igneous volcanic rocks (to differentiate them from igneous rocks that form from magma below the surface, called igneous plutonic rocks ). The lavas of different volcanoes, when cooled and hardened, differ much in their appearance and composition. If a rhyolite lava-stream cools quickly, it can quickly freeze into

781-405: A handful of sands of different colours and mixes them together, as they'll eventually separate into a layered spectrum. The place has become one of Mauritius' main tourist attractions since the 1960s. Nowadays, the dunes are protected by a wooden fence and visitors are not allowed to climb on them, although they can look at the scenery from observation outposts placed along the fence. Curio shops in

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852-563: A high affinity for the sodium ion; derivatives of the alkalide Na are obtainable by the addition of cryptands to solutions of sodium in ammonia via disproportionation . Many organosodium compounds have been prepared. Because of the high polarity of the C-Na bonds, they behave like sources of carbanions (salts with organic anions ). Some well-known derivatives include sodium cyclopentadienide (NaC 5 H 5 ) and trityl sodium ((C 6 H 5 ) 3 CNa). Sodium naphthalene , Na [C 10 H 8 •] ,

923-415: A high neutron flux in the reactor. The high boiling point of sodium allows the reactor to operate at ambient (normal) pressure, but drawbacks include its opacity, which hinders visual maintenance, and its strongly reducing properties. Sodium will explode in contact with water, although it will only burn gently in air. Radioactive sodium-24 may be produced by neutron bombardment during operation, posing

994-463: A nutrient for animals including humans. Sodium is an essential element for all animals and some plants. Sodium ions are the major cation in the extracellular fluid (ECF) and as such are the major contributor to the ECF osmotic pressure . Animal cells actively pump sodium ions out of the cells by means of the sodium–potassium pump , an enzyme complex embedded in the cell membrane , in order to maintain

1065-462: A paramorph of augite and magnetite, which may partially or completely substitute for the original crystal but still retains its characteristic outlines. The mechanical behaviour of volcanic rocks is complicated by their complex microstructure. For example, attributes such as the partitioning of the void space (pores and microcracks), pore and crystal size and shape, and hydrothermal alteration can all vary widely in volcanic rocks and can all influence

1136-885: A result, sodium usually forms ionic compounds involving the Na cation. Metallic sodium is generally less reactive than potassium and more reactive than lithium . Sodium metal is highly reducing, with the standard reduction potential for the Na /Na couple being −2.71 volts, though potassium and lithium have even more negative potentials. Sodium compounds are of immense commercial importance, being particularly central to industries producing glass , paper , soap , and textiles . The most important sodium compounds are table salt (Na Cl ), soda ash (Na 2 CO 3 ), baking soda (Na HCO 3 ), caustic soda (NaOH), sodium nitrate (Na NO 3 ), di- and tri- sodium phosphates , sodium thiosulfate (Na 2 S 2 O 3 ·5H 2 O), and borax (Na 2 B 4 O 7 ·10H 2 O). In compounds, sodium

1207-495: A result, the committee has established Adequate Intake (AI) levels instead, as follows. The sodium AI for infants of 0–6 months is established at 110 mg/day, 7–12 months: 370 mg/day; for children 1–3 years: 800 mg/day, 4–8 years: 1,000 mg/day; for adolescents: 9–13 years – 1,200 mg/day, 14–18 years 1,500 mg/day; for adults regardless of their age or sex: 1,500 mg/day. Sodium chloride ( NaCl ) contains approximately 39.34% of elemental sodium ( Na )

1278-421: A roughly ten-times higher concentration of sodium ions outside the cell than inside. In nerve cells , the sudden flow of sodium ions into the cell through voltage-gated sodium channels enables transmission of a nerve impulse in a process called the action potential . Sodium at standard temperature and pressure is a soft silvery metal that combines with oxygen in the air, forming sodium oxides . Bulk sodium

1349-461: A slight radiation hazard; the radioactivity stops within a few days after removal from the reactor. If a reactor needs to be shut down frequently, NaK is used. Because NaK is a liquid at room temperature, the coolant does not solidify in the pipes. In this case, the pyrophoricity of potassium requires extra precautions to prevent and detect leaks. Another heat transfer application is poppet valves in high-performance internal combustion engines;

1420-408: A strong reducing agent, forms upon mixing Na and naphthalene in ethereal solutions. Sodium forms alloys with many metals, such as potassium, calcium , lead , and the group 11 and 12 elements. Sodium and potassium form KNa 2 and NaK . NaK is 40–90% potassium and it is liquid at ambient temperature . It is an excellent thermal and electrical conductor. Sodium-calcium alloys are by-products of

1491-499: A volcanic rock's origin. The chemical classification of igneous rocks is based first on the total content of silicon and alkali metals ( sodium and potassium ) expressed as weight fraction of silica and alkali oxides ( K 2 O plus Na 2 O ). These place the rock in one of the fields of the TAS diagram . Ultramafic rock and carbonatites have their own specialized classification, but these rarely occur as volcanic rocks. Some fields of

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1562-630: Is a chemical element ; it has symbol   Na (from Neo-Latin natrium ) and atomic number  11. It is a soft, silvery-white, highly reactive metal . Sodium is an alkali metal , being in group 1 of the periodic table. Its only stable isotope is Na. The free metal does not occur in nature and must be prepared from compounds. Sodium is the sixth most abundant element in the Earth's crust and exists in numerous minerals such as feldspars , sodalite , and halite (NaCl). Many salts of sodium are highly water-soluble: sodium ions have been leached by

1633-401: Is a molten liquid and rock is solid). "Lava stone" may describe anything from a friable silicic pumice to solid mafic flow basalt, and is sometimes used to describe rocks that were never lava , but look as if they were (such as sedimentary limestone with dissolution pitting ). To convey anything about the physical or chemical properties of the rock, a more specific term should be used;

1704-411: Is dependent on two things: the initial composition of the primary magma and the subsequent differentiation. Differentiation of most magmas tends to increase the silica ( SiO 2 ) content, mainly by crystal fractionation . The initial composition of most magmas is basaltic , albeit small differences in initial compositions may result in multiple differentiation series. The most common of these series are

1775-457: Is dissolved in ammonia solution, it can be used to reduce alkynes to trans- alkenes . Lasers emitting light at the sodium D line are used to create artificial laser guide stars that assist in the adaptive optics for land-based visible-light telescopes. Liquid sodium is used as a heat transfer fluid in sodium-cooled fast reactors because it has the high thermal conductivity and low neutron absorption cross section required to achieve

1846-456: Is less electropositive than sodium, no calcium will be deposited at the cathode. This method is less expensive than the previous Castner process (the electrolysis of sodium hydroxide ). If sodium of high purity is required, it can be distilled once or several times. The market for sodium is volatile due to the difficulty in its storage and shipping; it must be stored under a dry inert gas atmosphere or anhydrous mineral oil to prevent

1917-531: Is seen in any whose surfaces are cool enough for sodium to exist in atomic form (rather than ionised). This corresponds to stars of roughly F-type and cooler. Many other stars appear to have a sodium absorption line, but this is actually caused by gas in the foreground interstellar medium . The two can be distinguished via high-resolution spectroscopy, because interstellar lines are much narrower than those broadened by stellar rotation . Sodium has also been detected in numerous Solar System environments, including

1988-462: Is stable. Na is created in the carbon-burning process in stars by fusing two carbon atoms together; this requires temperatures above 600 megakelvins and a star of at least three solar masses. Two radioactive , cosmogenic isotopes are the byproduct of cosmic ray spallation : Na has a half-life of 2.6 years and Na, a half-life of 15 hours; all other isotopes have a half-life of less than one minute. Two nuclear isomers have been discovered,

2059-549: Is the principal source of sodium ( Na ) in the diet, and is used as seasoning and preservative in such commodities as pickled preserves and jerky ; for Americans, most sodium chloride comes from processed foods . Other sources of sodium are its natural occurrence in food and such food additives as monosodium glutamate (MSG), sodium nitrite , sodium saccharin, baking soda (sodium bicarbonate), and sodium benzoate . The U.S. Institute of Medicine set its tolerable upper intake level for sodium at 2.3 grams per day, but

2130-622: Is to melt them together and another is to deposit sodium electrolytically on molten lead cathodes. NaPb 3 , NaPb, Na 9 Pb 4 , Na 5 Pb 2 , and Na 15 Pb 4 are some of the known sodium-lead alloys. Sodium also forms alloys with gold (NaAu 2 ) and silver (NaAg 2 ). Group 12 metals ( zinc , cadmium and mercury ) are known to make alloys with sodium. NaZn 13 and NaCd 2 are alloys of zinc and cadmium. Sodium and mercury form NaHg, NaHg 4 , NaHg 2 , Na 3 Hg 2 , and Na 3 Hg. Because of its importance in human health, salt has long been an important commodity. In medieval Europe,

2201-628: Is usually ionically bonded to water and anions and is viewed as a hard Lewis acid . Most soaps are sodium salts of fatty acids . Sodium soaps have a higher melting temperature (and seem "harder") than potassium soaps. Like all the alkali metals , sodium reacts exothermically with water. The reaction produces caustic soda ( sodium hydroxide ) and flammable hydrogen gas. When burned in air, it forms primarily sodium peroxide with some sodium oxide . Sodium tends to form water-soluble compounds, such as halides , sulfates , nitrates , carboxylates and carbonates . The main aqueous species are

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2272-469: Is usually stored in oil or an inert gas. Sodium metal can be easily cut with a knife. It is a good conductor of electricity and heat. Due to having low atomic mass and large atomic radius, sodium is third-least dense of all elemental metals and is one of only three metals that can float on water, the other two being lithium and potassium. The melting (98 °C) and boiling (883 °C) points of sodium are lower than those of lithium but higher than those of

2343-582: The Sun . The line was first studied in 1814 by Joseph von Fraunhofer during his investigation of the lines in the solar spectrum, now known as the Fraunhofer lines . Fraunhofer named it the "D" line, although it is now known to actually be a group of closely spaced lines split by a fine and hyperfine structure . The strength of the D ;line allows its detection in many other astronomical environments. In stars, it

2414-468: The electrolysis of sodium hydroxide . In 1809, the German physicist and chemist Ludwig Wilhelm Gilbert proposed the names Natronium for Humphry Davy's "sodium" and Kalium for Davy's "potassium". The chemical abbreviation for sodium was first published in 1814 by Jöns Jakob Berzelius in his system of atomic symbols, and is an abbreviation of the element's Neo-Latin name natrium , which refers to

2485-463: The exospheres of Mercury and the Moon , and numerous other bodies. Some comets have a sodium tail , which was first detected in observations of Comet Hale–Bopp in 1997. Sodium has even been detected in the atmospheres of some extrasolar planets via transit spectroscopy . Employed in rather specialized applications, about 100,000 tonnes of metallic sodium are produced annually. Metallic sodium

2556-408: The pyroxenes . Bowen's reaction series correctly predicts the order of formation of the most common minerals in volcanic rocks. Occasionally, a magma may pick up crystals that crystallized from another magma; these crystals are called xenocrysts . Diamonds found in kimberlites are rare but well-known xenocrysts; the kimberlites do not create the diamonds, but pick them up and transport them to

2627-558: The sixth most abundant element on Earth and the fourth most abundant metal, behind aluminium , iron , calcium , and magnesium and ahead of potassium. Sodium's estimated oceanic abundance is 10.8 grams per liter. Because of its high reactivity, it is never found as a pure element. It is found in many minerals, some very soluble, such as halite and natron , others much less soluble, such as amphibole and zeolite . The insolubility of certain sodium minerals such as cryolite and feldspar arises from their polymeric anions, which in

2698-562: The tholeiitic , calc-alkaline , and alkaline . Most volcanic rocks share a number of common minerals . Differentiation of volcanic rocks tends to increase the silica (SiO 2 ) content mainly by fractional crystallization . Thus, more evolved volcanic rocks tend to be richer in minerals with a higher amount of silica such as phyllo and tectosilicates including the feldspars, quartz polymorphs and muscovite . While still dominated by silicates, more primitive volcanic rocks have mineral assemblages with less silica, such as olivine and

2769-427: The Earth's current land surface. Volcanic rocks are usually fine-grained or aphanitic to glass in texture. They often contain clasts of other rocks and phenocrysts . Phenocrysts are crystals that are larger than the matrix and are identifiable with the unaided eye . Rhomb porphyry is an example with large rhomb shaped phenocrysts embedded in a very fine grained matrix. Volcanic rocks often have

2840-513: The Egyptian natron , a natural mineral salt mainly consisting of hydrated sodium carbonate. Natron historically had several important industrial and household uses, later eclipsed by other sodium compounds. Sodium imparts an intense yellow color to flames. As early as 1860, Kirchhoff and Bunsen noted the high sensitivity of a sodium flame test , and stated in Annalen der Physik und Chemie : In

2911-621: The TAS diagram are further subdivided by the ratio of potassium oxide to sodium oxide. Additional classifications may be made on the basis of other components, such as aluminum or iron content. Volcanic rocks are also broadly divided into subalkaline, alkaline, and peralkaline volcanic rocks. Subalkaline rocks are defined as rocks in which SiO 2 < -3.3539 × 10 × A + 1.2030 × 10 × A - 1.5188 × 10 × A + 8.6096 × 10 × A - 2.1111 × A + 3.9492 × A + 39.0 where both silica and total alkali oxide content (A) are expressed as molar fraction . Because

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2982-436: The TAS diagram uses weight fraction and the boundary between alkaline and subalkaline rock is defined in terms of molar fraction, the position of this curve on the TAS diagram is only approximate. Peralkaline volcanic rocks are defined as rocks having Na 2 O + K 2 O > Al 2 O 3 , so that some of the alkali oxides must be present as aegirine or sodic amphibole rather than feldspar . The chemistry of volcanic rocks

3053-465: The action of water from the Earth's minerals over eons, and thus sodium and chlorine are the most common dissolved elements by weight in the oceans. Sodium was first isolated by Humphry Davy in 1807 by the electrolysis of sodium hydroxide . Among many other useful sodium compounds, sodium hydroxide ( lye ) is used in soap manufacture , and sodium chloride ( edible salt ) is a de-icing agent and

3124-689: The aquo complexes [Na(H 2 O) n ] , where n = 4–8; with n = 6 indicated from X-ray diffraction data and computer simulations. Direct precipitation of sodium salts from aqueous solutions is rare because sodium salts typically have a high affinity for water. An exception is sodium bismuthate (NaBiO 3 ), which is insoluble in cold water and decomposes in hot water. Because of the high solubility of its compounds, sodium salts are usually isolated as solids by evaporation or by precipitation with an organic antisolvent, such as ethanol ; for example, only 0.35 g/L of sodium chloride will dissolve in ethanol. A crown ether such as 15-crown-5 may be used as

3195-646: The area sell small test-tubes filled up with the coloured earths. This Mauritius location article is a stub . You can help Misplaced Pages by expanding it . Volcanic rock Volcanic rocks (often shortened to volcanics in scientific contexts) are rocks formed from lava erupted from a volcano . Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and metamorphic rocks and constitute an important element of some sediments and sedimentary rocks . For these reasons, in geology, volcanics and shallow hypabyssal rocks are not always treated as distinct. In

3266-428: The ascent from the subterranean depths to the crater of the volcano. It has frequently been verified by observation that freshly emitted lavas contain large crystals borne along in a molten, liquid mass. The large, well-formed, early crystals ( phenocrysts ) are said to be porphyritic ; the smaller crystals of the surrounding matrix or ground-mass belong to the post-effusion stage. More rarely lavas are completely fused at

3337-689: The average person in the United States consumes 3.4 grams per day. The American Heart Association recommends no more than 1.5 g of sodium per day. The Committee to Review the Dietary Reference Intakes for Sodium and Potassium, which is part of the National Academies of Sciences, Engineering, and Medicine, has determined that there isn't enough evidence from research studies to establish Estimated Average Requirement (EAR) and Recommended Dietary Allowance (RDA) values for sodium. As

3408-423: The case of feldspar is a polysilicate. In the universe, sodium is the 15th most abundant element with a 20,000 parts-per-billion abundance, making sodium 0.002% of the total atoms in the universe. Atomic sodium has a very strong spectral line in the yellow-orange part of the spectrum (the same line as is used in sodium-vapour street lights ). This appears as an absorption line in many types of stars, including

3479-476: The causes of their consistent spontaneous separation are yet to be fully clarified. The name "Seven Coloured Earth(s)" is a descriptive—rather than an official—name. Sources report many variations of this name, including "Chamarel Seven Coloured Earths", "Chamarel Coloured Earth(s)", "Coloured Earth", and Terres des Sept Couleurs in French . This phenomenon can also be observed, on a smaller scale, if one takes

3550-520: The context of Precambrian shield geology, the term "volcanic" is often applied to what are strictly metavolcanic rocks . Volcanic rocks and sediment that form from magma erupted into the air are called "pyroclastics," and these are also technically sedimentary rocks. Volcanic rocks are among the most common rock types on Earth's surface, particularly in the oceans. On land, they are very common at plate boundaries and in flood basalt provinces . It has been estimated that volcanic rocks cover about 8% of

3621-433: The crystal. It is clear that after the mineral had crystallized it was partly again dissolved or corroded at some period before the matrix solidified. Corroded phenocrysts of biotite and hornblende are very common in some lavas; they are surrounded by black rims of magnetite mixed with pale green augite. The hornblende or biotite substance has proved unstable at a certain stage of consolidation, and has been replaced by

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3692-431: The electrolytic production of sodium from a binary salt mixture of NaCl-CaCl 2 and ternary mixture NaCl-CaCl 2 -BaCl 2 . Calcium is only partially miscible with sodium, and the 1–2% of it dissolved in the sodium obtained from said mixtures can be precipitated by cooling to 120 °C and filtering. In a liquid state, sodium is completely miscible with lead. There are several methods to make sodium-lead alloys. One

3763-420: The formation of a surface layer of sodium oxide or sodium superoxide . Though metallic sodium has some important uses, the major applications for sodium use compounds; millions of tons of sodium chloride , hydroxide , and carbonate are produced annually. Sodium chloride is extensively used for anti-icing and de-icing and as a preservative; examples of the uses of sodium bicarbonate include baking, as

3834-404: The ground-mass . Microscopic examination of the phenocrysts often reveals that they have had a complex history. Very frequently they show layers of different composition, indicated by variations in color or other optical properties; thus augite may be green in the center surrounded by various shades of brown; or they may be pale green centrally and darker green with strong pleochroism (aegirine) at

3905-435: The heavier alkali metals potassium, rubidium, and caesium, following periodic trends down the group. These properties change dramatically at elevated pressures: at 1.5  Mbar , the color changes from silvery metallic to black; at 1.9 Mbar the material becomes transparent with a red color; and at 3 Mbar, sodium is a clear and transparent solid. All of these high-pressure allotropes are insulators and electrides . In

3976-517: The longer-lived one being Na with a half-life of around 20.2 milliseconds. Acute neutron radiation, as from a nuclear criticality accident , converts some of the stable Na in human blood to Na; the neutron radiation dosage of a victim can be calculated by measuring the concentration of Na relative to Na. Sodium atoms have 11 electrons, one more than the stable configuration of the noble gas neon . The first and second ionization energies are 495.8 kJ/mol and 4562 kJ/mol, respectively. As

4047-430: The mechanical behaviour of volcanic rocks can help us better understand volcanic hazards, such as flank collapse. Volcanic rocks : Subvolcanic rocks : Plutonic rocks : Picrite basalt Peridotite Basalt Diabase (Dolerite) Gabbro Andesite Microdiorite Diorite Dacite Microgranodiorite Granodiorite Rhyolite Microgranite Granite Sodium Sodium

4118-714: The moment of ejection; they may then cool to form a non-porphyritic, finely crystalline rock, or if more rapidly chilled may in large part be non-crystalline or glassy (vitreous rocks such as obsidian, tachylyte , pitchstone ). A common feature of glassy rocks is the presence of rounded bodies ( spherulites ), consisting of fine divergent fibres radiating from a center; they consist of imperfect crystals of feldspar, mixed with quartz or tridymite ; similar bodies are often produced artificially in glasses that are allowed to cool slowly. Rarely these spherulites are hollow or consist of concentric shells with spaces between ( lithophysae ). Perlitic structure, also common in glasses, consists of

4189-462: The need for large quantities of sodium. A related process based on the reduction of sodium hydroxide was developed in 1886. Sodium is now produced commercially through the electrolysis of molten sodium chloride (common salt), based on a process patented in 1924. This is done in a Downs cell in which the NaCl is mixed with calcium chloride to lower the melting point below 700 °C. As calcium

4260-409: The periphery. In the feldspars the center is usually richer in calcium than the surrounding layers, and successive zones may often be noted, each less calcic than those within it. Phenocrysts of quartz (and of other minerals), instead of sharp, perfect crystalline faces, may show rounded corroded surfaces, with the points blunted and irregular tongue-like projections of the matrix into the substance of

4331-441: The positive charge counterbalanced by electrons as anions ; cryptands permit the isolation of these complexes as crystalline solids. Sodium forms complexes with crown ethers, cryptands and other ligands. For example, 15-crown-5 has a high affinity for sodium because the cavity size of 15-crown-5 is 1.7–2.2 Å, which is enough to fit the sodium ion (1.9 Å). Cryptands, like crown ethers and other ionophores , also have

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4402-454: The presence of concentric rounded cracks owing to contraction on cooling. The phenocrysts or porphyritic minerals are not only larger than those of the ground-mass; as the matrix was still liquid when they formed they were free to take perfect crystalline shapes, without interference by the pressure of adjacent crystals. They seem to have grown rapidly, as they are often filled with enclosures of glassy or finely crystalline material like that of

4473-452: The pressure increases. By itself or with potassium , sodium is a desiccant ; it gives an intense blue coloration with benzophenone when the desiccate is dry. In organic synthesis , sodium is used in various reactions such as the Birch reduction , and the sodium fusion test is conducted to qualitatively analyse compounds. Sodium reacts with alcohols and gives alkoxides , and when sodium

4544-561: The product of explosive volcanism. They are often felsic (high in silica). Pyroclastic rocks are often the result of volcanic debris, such as ash , bombs and tephra , and other volcanic ejecta . Examples of pyroclastic rocks are tuff and ignimbrite . Shallow intrusions , which possess structure similar to volcanic rather than plutonic rocks, are also considered to be volcanic, shading into subvolcanic . The terms lava stone and lava rock are more used by marketers than geologists, who would likely say "volcanic rock" (because lava

4615-478: The resultant mechanical behaviour (e.g., Young's modulus, compressive and tensile strength, and the pressure at which they transition from brittle to ductile behaviour ). As for other crustal rocks, volcanic rocks are brittle and ductile at low and high effective confining pressures, respectively. Brittle behaviour is manifest as faults and fractures, and ductile behaviour can either be distributed (cataclastic pore collapse) or localised (compaction bands). Understanding

4686-455: The surface of the Earth. Volcanic rocks are named according to both their chemical composition and texture. Basalt is a very common volcanic rock with low silica content. Rhyolite is a volcanic rock with high silica content. Rhyolite has silica content similar to that of granite while basalt is compositionally equal to gabbro . Intermediate volcanic rocks include andesite , dacite , trachyte , and latite . Pyroclastic rocks are

4757-476: The valve stems are partially filled with sodium and work as a heat pipe to cool the valves. In humans, sodium is an essential mineral that regulates blood volume, blood pressure, osmotic equilibrium and pH . The minimum physiological requirement for sodium is estimated to range from about 120 milligrams per day in newborns to 500 milligrams per day over the age of 10. Sodium chloride , also known as edible salt or table salt (chemical formula NaCl ),

4828-514: Was first produced commercially in the late nineteenth century by carbothermal reduction of sodium carbonate at 1100 °C, as the first step of the Deville process for the production of aluminium: The high demand for aluminium created the need for the production of sodium. The introduction of the Hall–Héroult process for the production of aluminium by electrolysing a molten salt bath ended

4899-453: Was going on while the mass was still creeping forward under the surface of the Earth, the latest formed minerals (in the ground-mass ) are commonly arranged in subparallel winding lines that follow the direction of movement (fluxion or fluidal structure)—and larger early minerals that previously crystallized may show the same arrangement. Most lavas fall considerably below their original temperatures before emitted. In their behavior, they present

4970-480: Was still liquid at the moment of eruption. At this time they were exposed only to atmospheric pressure, and the steam and other gases, which they contained in great quantity were free to escape; many important modifications arise from this, the most striking being the frequent presence of numerous steam cavities ( vesicular structure) often drawn out to elongated shapes subsequently filled up with minerals by infiltration ( amygdaloidal structure). As crystallization

5041-554: Was the making of tetraethyllead and titanium metal; because of the move away from TEL and new titanium production methods, the production of sodium declined after 1970. Sodium is also used as an alloying metal, an anti-scaling agent , and as a reducing agent for metals when other materials are ineffective. Note the free element is not used as a scaling agent, ions in the water are exchanged for sodium ions. Sodium plasma ("vapor") lamps are often used for street lighting in cities, shedding light that ranges from yellow-orange to peach as

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