Lithium

  Fraser Cain (16th Aug 2006). "Why Old Stars Seem to Lack Lithium". http://www.universetoday.com/2006/08/16/why-old-stars-seem-to-lack-lithium/. I.-Juliana Sackmann and Arnold I. Boothroyd

Lithium

Информация

Иностранные языки

Другие материалы по предмету

Иностранные языки

Сдать работу со 100% гаранией
rmone hypersecretion (SIADH). It was also sometimes prescribed as a preventive treatment for migraine disease and cluster headaches.[53]

The active principle in these salts is the lithium ion Li+. Although this ion has a smaller diameter than either Na+ or K+, in a watery environment like the cytoplasmic fluid, Li+ binds to the hydrogen atoms of water, making it effectively larger than either Na+ or K+ ions. How Li+ works in the central nervous system is still a matter of debate. Li+ elevates brain levels of tryptophan, 5-HT (serotonin), and 5-HIAA (a serotonin metabolite). Serotonin is related to mood stability. Li+ also reduces catecholamine activity in the brain (associated with brain activation and mania), by enhancing reuptake and reducing release. Therapeutically useful amounts of lithium (~ 0.6 to 1.2 mmol/l) are only slightly lower than toxic amounts (>1.5 mmol/l), so the blood levels of lithium must be carefully monitored during treatment to avoid toxicity.

Common side effects of lithium treatment include muscle tremors, twitching, ataxia[54] and hypothyroidism. Long term use is linked to hyperparathyroidism[55], hypercalcemia (bone loss), hypertension, kidney damage, nephrogenic diabetes insipidus (polyuria and polydipsia), seizures[56] and weight gain.[57] Some of the side-effects are a result of the increased elimination of potassium.

There appears to be an increased risk of Ebstein (cardiac) Anomaly in infants born to women taking lithium during the first trimester of pregnancy.

According to a study in 2009 at Oita University in Japan and published in the British Journal of Psychiatry, communities whose water contained larger amounts of lithium had significantly lower suicide rates[58][59][60][61] but did not address whether lithium in drinking water causes the negative side effects associated with higher doses of the element.[62]

 

6.2 Other uses

 

Electrical and electronic uses:

Lithium batteries are disposable (primary) batteries with lithium metal or lithium compounds as an anode. Lithium batteries are not to be confused with lithium-ion batteries, which are high energy-density rechargeable batteries. Other rechargeable batteries include the Lithium-ion polymer battery, Lithium iron phosphate battery, and the Nanowire battery. New technologies are constantly being announced.

Lithium niobate is used extensively in telecommunication products such as mobile phones and optical modulators, for such components as resonant crystals. Lithium applications are used in more than 60% of mobile phones.[63]

Chemical uses:

Lithium chloride and lithium bromide are extremely hygroscopic and are used as desiccants.

Lithium metal is used in the preparation of organo-lithium compounds.

General engineering:

lithium stearate is a common all-purpose, high-temperature lubricant.

When used as a flux for welding or soldering, lithium promotes the fusing of metals during and eliminates the forming of oxides by absorbing impurities. Its fusing quality is also important as a flux for producing ceramics, enamels and glass.

Alloys of the metal with aluminium, cadmium, copper and manganese are used to make high-performance aircraft parts (see also Lithium-aluminium alloys).

Optics:

Lithium is sometimes used in focal lenses, including spectacles and the glass for the 200-inch (5.08 m) telescope at Mt. Palomar.[citation needed]

The high non-linearity of lithium niobate also makes it useful in non-linear optics applications.

Lithium fluoride, artificially grown as crystal, is clear and transparent and often used in specialist optics for IR, UV and VUV (vacuum UV) applications. It has the lowest refractive index and the farthest transmission range in the deep UV of all common materials.

Rocketry:

Metallic lithium and its complex hydrides, such a Li[AlH4], are used as high energy additives to rocket propellants[3].

Lithium peroxide, lithium nitrate, lithium chlorate and lithium perchlorate are used as oxidizers in rocket propellants, and also in oxygen candles that supply submarines and space capsules with oxygen.[64]

Nuclear applications:

Lithium deuteride was the fusion fuel of choice in early versions of the hydrogen bomb. When bombarded by neutrons, both 6Li and 7Li produce tritiumthis reaction, which was not fully understood when hydrogen bombs were first tested, was responsible for the runaway yield of the Castle Bravo nuclear test. Tritium fuses with deuterium in a fusion reaction that is relatively easy to achieve. Although details remain secret, lithium-6 deuteride still apparently plays a role in modern nuclear weapons, as a fusion material.

Lithium fluoride (highly enriched in the common isotope lithium-7) forms the basic constituent of the preferred fluoride salt mixture (LiF-BeF2) used in liquid-fluoride nuclear reactors. Lithium fluoride is exceptionally chemically stable and LiF/BeF2 mixtures have low melting points and the best neutronic properties of fluoride salt combinations appropriate for reactor use.[clarification needed]

In conceptualized nuclear fusion power plants, lithium will be used to produce tritium in magnetically confined reactors using deuterium and tritium as the fuel. Tritium does not occur naturally and will be produced by surrounding the reacting plasma with a 'blanket' containing lithium where neutrons from the deuterium-tritium reaction in the plasma will react with the lithium to produce more tritium. 6Li + n → 4He + 3H. Various means of doing this will be tested at the ITER reactor being built at Cadarache, France.

Lithium is used as a source for alpha particles, or helium nuclei. When 7Li is bombarded by accelerated protons 8Be is formed, which undergoes spontaneous fission to form two alpha particles. This was the first man-made nuclear reaction, produced by Cockroft and Walton in 1929.

Other uses:

Lithium hydroxide (LiOH) is an important compound of lithium obtained from lithium carbonate (Li2CO3). It is a strong base, and when heated with a fat it produces a lithium soap. Lithium soap has the ability to thicken oils, and it is used to manufacture lubricating greases.

Lithium hydroxide and lithium peroxide are used in confined areas, such as aboard spacecraft and submarines, for air purification. Lithium hydroxide absorbs carbon dioxide from the air by reacting with it to form lithium carbonate, and is preferred over other alkaline hydroxides for its low weight. Lithium peroxide (Li2O2) in presence of moisture not only absorbs carbon dioxide to form lithium carbonate, but also releases oxygen. For example 2 Li2O2 + 2 CO2 → 2 Li2CO3 + O2.

Lithium compounds are used in red fireworks and flares.

The Mark 50 Torpedo Stored Chemical Energy Propulsion System (SCEPS) uses a small tank of sulfur hexafluoride gas which is sprayed over a block of solid lithium. The reaction generates enormous heat which is used to generate steam from seawater. The steam propels the torpedo in a closed Rankine cycle.[65]

 

Figure. 5. The red lithium flame leads to lithium's use in flares and pyrotechnics

 

7. Precautions

 

Due to its alkaline tarnish, lithium metal is corrosive and requires special handling to avoid skin contact. Breathing lithium dust or lithium compounds (which are often alkaline) initially irritate the nose and throat, while higher exposure can cause a buildup of fluid in the lungs, leading to pulmonary edema. The metal itself is a handling hazard because of the caustic hydroxide produced when it is in contact with moisture. Lithium is safely stored in non-reactive compounds such as naphtha.[66]

 

Figure. 6. Lithium ingots with a thin layer of black oxide tarnish

 

7.1 Regulation

 

Some jurisdictions limit the sale of lithium batteries, which are the most readily available source of lithium metal for ordinary consumers. Lithium can be used to reduce pseudoephedrine and ephedrine to methamphetamine in the Birch reduction method, which employs solutions of alkali metals dissolved in anhydrous ammonia.

Carriage and shipment of some kinds of lithium batteries may be prohibited aboard certain types of transportation (particularly aircraft) because of the ability of most types of lithium batteries to fully discharge very rapidly when short-circuited, leading to overheating and possible explosion in a process called thermal runaway. Most consumer lithium batteries have thermal overload protection built-in to prevent this type of incident, or their design inherently limits short-circuit currents. Internal shorts have been known to develop due to manufacturing defects or damage to batteries that can lead to spontaneous thermal runaway.[67]

8. Conclusion

 

As an individual representative of the periodic table of chemical elements Dmitry Ivanovich Mendeleyev, the element has unique chemical and physical properties

Element is of great economic importance and plays a major role in world culture

9. References

 

  1. Fraser Cain (16th Aug 2006). "Why Old Stars Seem to Lack Lithium". http://www.universetoday.com/2006/08/16/why-old-stars-seem-to-lack-lithium/.
  2. I.-Juliana Sackmann and Arnold I. Boothroyd (1995). "Lithium Creation In Giant Stars". Proc. of IAU General Assembly "Lithium Joint Discussion 11", ed. F. Spite and R. Pallavicini, Memorie della Societa Astronomica Italiana 66: 403-412. http://www.cita.utoronto.ca/~boothroy/lijd11.html.
  3. Leonid S. Marochnik, Anwar Shukurov, Igor Yastrzhembsky, (1996). Th

Похожие работы

<< < 1 2 3 4 >