Diamond

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Rabu, 12 Oktober 2011

http://www.scienceviews.com/geology/minerals.htm

Minerals and Their Uses

Every segment of society uses minerals and mineral resources everyday. The roads we ride or drive on and the buildings we live learn and work in all contain minerals. Below is a selected list of commonly used metallic and nonmetallic minerals, ore minerals, mineral byproducts, aggregates, and rock types that are used to make products we use in our daily life.

Aggregates
Natural aggregates include sand, gravel, and crushed stone. Aggregates are composed of rock fragments that may be used in their natural state or after mechanical processing, such as crushing, washing, or sizing. Recycled aggregates consist mainly of crushed concrete and crushed asphalt pavement.
Aluminum
Aluminum is the most abundant metallic element in the Earth's crust. Bauxite ore is the main source of aluminum. Aluminum is used in automobiles and airplanes (36%), bottling and canning industries (25%), building and electrical (14%) and in other applications (25%). Antimony
Antimony
Antimony is a silvery-gray, brittle semi-metal. It rarely occurs in nature as a native element, but is found in a number of different minerals. Antimony is used principally for flame retardants as well as in ammunition and automotive batteries and as a decolorizing agent in glassmaking.

Asbestos
Asbestos
Asbestos is a class of minerals that can be readily separated into thin, strong fibers that are flexible, heat resistant, and chemically inert. Asbestos minerals are used in fireproof fabrics, yarn, cloth, and paper and paint filler. Asbestos is used to make friction products, asbestos cement pipes and sheets, coatings and compounds, packing and gaskets, roofing and flooring products, paints and caulking, and chemical filters. Fibers are dangerous when breathed, so users must protect against fibers becoming airborne.

Basalt
Basalt
Basalt is an extrusive igneous rock. Crushed basalt is used for railroad ballast, aggregate in highway construction, and is a major component of asphalt.

Barium
Barium
Barium is an element, derived primarily from the mineral barite, and used as a heavy additive in oil-well-drilling mud, paints, rubber, plastic and paper; production of barium chemicals; and glass manufacturing. Beryllium
Beryllium
Beryllium, an element commonly associated with igneous rocks, has industrial and nuclear defense applications and is used in light, very strong alloys for the aircraft industry. Beryllium salts are used in x-ray tubes and as a deoxidizer in bronze metallurgy. The gemstones of beryl, a beryllium mineral, are emerald and aquamarine. Bismuth
Bismuth
Bismuth is used in a number of very different applications. The majority is consumed in bismuth alloys, and in pharmaceuticals and chemicals. The remainder is used in ceramics, paints, catalysts, and a variety of minor applications. Bismuth metal is relatively inert and non-toxic. It has replaced toxic lead in many applications such as plumbing, bullets, birdshot, metal alloys, and soldering. Bismuth compounds are used in stomach-upset medicines (hence the trademarked name Pepto-Bismol), treatment of stomach ulcers, soothing creams, and cosmetics. Boron
Boron
Boron compounds are used for many different purposes in industry and the home. Boron is used to make glass, ceramics, enamels, fiberglass, make water softeners, soaps and detergents. Other uses are in agricultural chemicals, pest controls, fire retardants, fireworks, medicine, and various minor applications. Boron nitride is one of the hardest known substances and is used for abrasives and cutting tools.
Bromine
Bromine, recovered commercially through the treatment of seawater brines, is used in leaded gasoline, fire extinguishers and retardants, well-completion fluids, and sanitary preparations. Bromine is the only liquid nonmetallic element.
Cadmium
Cadmium is used in plating and alloying, pigments, plastics, and batteries. Cadmium is obtained from the ore minerals Sphalerite (Zn,Cd)S and Greenockite (CdS) Calcium
Calcium
The primary use of calcium is not in its silvery-white metal form, but as calcium carbonate. It used in adhesives and sealants, cosmetics, foods, paint, paper, pharmaceuticals, plastics, rubber, for the production of lime, and as crhused stone in construction. Immense quantities of calcium are found in sedimentary rock deposits of gypsum, limestone, and shale. Some common calcium-bearing minerals include apatite (calcium phosphate), calcite (calcium carbonate), dolomite (calcium magnesium carbonate), fluorite (calcium fluoride), and gypsum (calcium sulfate). Calcium metal is produced in Canada, China, France, Russia, and the United States. Total world output is thought to be less than 6,000 metric tons per year. United States consumption of calcium metal is small. On a worldwide basis, more than 100 million metric tons per year of apatite and gypsum are mined, and calcite and dolomite are produced in billions of metric tons per year.
Cement
Cement is used for building materials, stucco, and mortar. Cement is :a mixture of powdered lime, clay, and other minerals that crystallize to form a hard solid when water is added (hydraulic cement) or as a binding material in concrete" (Kesler, 1994). An excellent overview of cement, its chemistry, and properties can be found in MacLaren and White (2003). Chromium
Chromium
Chromium is used in the production of stainless and heat-resistant steel, full-alloy steel, super alloys and other alloys. Chromium is obtained from the ore mineral Chromite (Mg,Fe)(Cr,Al,Fe)2O4
Clays
There are many different clay minerals that are used for industrial applications. Clays are used in the manufacturing of paper, refractories, rubber, ball clay, dinnerware and pottery, floor and wall tile, sanitary wear, fire clay, firebricks, foundry sands, drilling mud, iron-ore pelletizing, absorbent and filtering materials, construction materials, and cosmetics. Cobalt
Cobalt
Half of the consumption of cobalt is used in corrosion- and abrasion-resistant alloys with steel, nickel, and other metals for the production of industrial engines. Other uses of cobalt metal include magnets and cutting tools. Cobalt salts are used to produce a blue color in paint pigments, porcelain, glass, and pottery. Cobalt is obtained from the ore minerals Linneaite (Co3S4), Cobaltite CoAsS, and (Fe,Ni,Co)1-xSx. Copper
Copper
Copper is used in electric cables and wires, switches, plumbing; heating, electrical, and roofing materials; electronic components; industrial machinery and equipment; transportation; consumer and general products; coins; and jewelry.

Diamond
Diamond
Industrial diamonds are those that can not be used as gems. Large diamonds are used in tools and drilling bits to cut rock and small stone. Small diamonds, also known as dust or grit, are used for cutting and polishing stone and ceramic products.

Diatomite
Diatomite
Diatomite is a rock composed of the skeletons of diatoms, single-celled organisms with skeletons made of silica, which are found in fresh and salt water. Diatomite is primarily used for filtration of drinks, such as juices and wines, but it is also being used as filler in paints and pharmaceuticals and environmental cleanup technologies. Dolomite
Dolomite
Dolomite is the near twin-sister rock to limestone. Like limestone, it typically forms in a marine environment but also as has a primary magnesium component. Dolomite is used in agriculture, chemical and industrial applications, cement construction, refractories, and environmental industries. Feldspar
Feldspar
Feldspar is a rock-forming mineral. It is used in glass and ceramic industries; pottery, porcelain and enamelware; soaps; bond for abrasive wheels; cement; glues; fertilizer; and tarred roofing materials and as a sizing, or filler, in textiles and paper applications.

Fluorite
Fluorite
Fluorite is used in production of hydrofluoric acid, which is used in the pottery, ceramics, optical, electroplating, and plastics industries. It is also used in the metallurgical treatment of bauxite, as a flux in open-hearth steel furnaces, and in metal smelting, as well as in carbon electrodes, emery wheels, electric arc welders, and toothpaste as a source of fluorine. Garnet
Garnet
Garnet is used in water filtration, electronic components, ceramics, glass, jewelry, and abrasives used in wood furniture and transport manufacturing. "Garnet is a common metamorphic mineral that becomes abundant enough to mine in a few rocks" (Kesler, 1994).
Germanium
"Most germanium is recovered as a byproduct of zinc smelting. It is also found in some copper ores" (Kesler, 1994). Applications include use in fiber-optic components, which are replacing copper in long-distance telecommunication lines, as well as in camera lenses and other glasses and infrared lenses. Gold
Gold
Gold is used in dentistry and medicine, jewelry and arts, medallions and coins, and in ingots. It is also used for scientific and electronic instruments, computer circuitry, as an electrolyte in the electroplating industry, and in many applications for the aerospace industry. Granite
Granite
Granite can be cut into large blocks and used as a building stone. When polished, it is used for monuments, headstones, countertops, statues, and facing on buildings. It is also suitable for railroad ballast and for road aggregate in highway construction. Graphite
Graphite
Graphite is the crystal form of carbon. Graphite is used as a dry lubricant and steel hardener and for brake linings and the production of "lead" in pencils. Most graphite production comes from Korea, India, and Mexico. Gypsum
Gypsum
Processed gypsum is used in industrial or building plaster, prefabricated wallboard, cement manufacture, and for agriculture.

Halite
Halite
Halite (salt) is used in the human and animal diet, primarily as food seasoning and as a food preservation. It is also used to prepare sodium hydroxide, soda ash, caustic soda, hydrochloric acid, chlorine, and metallic sodium, and it is used in ceramic glazes, metallurgy, curing of hides, mineral waters, soap manufacture, home water softeners, highway deicing, photography, and scientific equipment for optical parts.
Iodine
Iodine is used as an antibacterial agent in soaps and cleaning products in restrooms, in iodized salt to prevent goiter, and in first aid boxes as an antiseptic. Iron 
Ore
Iron Ore
Iron ore is used to manufacture steels of various types and other metallurgical products, such as magnets, auto parts, and catalysts. Most U.S. production is from Minnesota and Michigan. The Earth's crust contains about 5% iron, the fourth most abundant element in the crust.

Lead
Lead
Lead is used in batteries, construction, ammunition, television tubes, nuclear shielding, ceramics, weights, and tubes or containers. The United States is largest producer (mainly from Missouri), consumer, and recycler of lead metal. Limestone
Limestone
"A sedimentary rock consisting largely of the minerals calcite and aragonite, which have the same composition CaCO3". Limestone, along with dolomite, is one of the basic building blocks of the construction industry. Limestone is used as aggregate, building stone, cement, and lime and in fluxes, glass, refractories, fillers, abrasives, soil conditioners, and a host of chemical processes. Lithium
Lithium
Batteries made from lithium metal or lithium carbonate are used in smoke alarms, pacemakers, defibrillator machines, many other types of portable medical equipment, and in emergency communications equipment, including computers and cell phones. Magnesium
Magnesium
Magnesium (see dolomite) is used in cement, rubber, paper, insulation, chemicals and fertilizers, animal feed, and pharmaceuticals. Magnesium is obtained from the ore minerals Olivine (Fe,Mg)2SiO4, Magnesite MgCO3, and Dolomite CaMg(CO3)2. Manganese
Manganese
Manganese is essential to iron and steel production. Manganese is obtained from the ore minerals Braunite (Mn,Si)2O3, Pyrolusite MnO2, and Psilomelane BaMn9O18*2H2O.

Mercury
Mercury
Mercury is extracted from the mineral cinnabar and is used in electrical products, electrolytic production of chlorine and caustic soda, paint, and industrial and control instruments (thermometers and thermostats). Mica
Mica
Mica minerals commonly occur as flakes, scales, or shreds. Sheet muscovite (white) mica is used in electronic insulators, paints, as joint cement, as a dusting agent, in welldrilling mud and lubricants, and in plastics, roofing, rubber, and welding rods. Molybdenum
Molybdenum
Molybdenum is used in stainless steels (21%), tool steels (9%), cast irons (7%), and chemical lubricants (8%), and in other applications (55%). It is commonly used to make automotive parts, construction equipment, gas transmission pipes, and as a pure metal molybdenum is used as filament supports in light bulbs, metalworking dies, and furnace parts because of its high melting temperature (2,623°C). Nickel
Nickel
Nickel is vital as an alloy to stainless steel, and it plays a key roll in the chemical and aerospace industries. Leading producers are Canada, Norway, and Russia.

Phosphate rock
Phosphate rock
Primarily a sedimentary rock used to produce phosphoric acid and ammoniated phosphate fertilizers, feed additives for livestock, elemental phosphorus, and a variety of phosphate chemicals for industrial and home consumers. The majority of U.S. production comes from Florida, North Carolina, Idaho, and Utah. Platinum
Platinum Group Metals (PGMs)
PGM's include platinum, palladium, rhodium, iridium, osmium, and ruthenium. These elements commonly occur together in nature and are among the scarcest of the metallic elements. Platinum is used principally in catalytic converters for the control of automobile and industrial plant emissions; in jewelry; in catalysts to produce acids, organic chemicals, and pharmaceuticals; and in dental alloys used for making crowns and bridges. Potash
Potash
Potash is an industry term that refers to a group of water-soluble salts containing the element potassium, as well as to ores containing these salts (Kesler, 1994). Potash is used in fertilizer, medicine, the chemical industry, and to produce decorative color effects on brass, bronze, and nickel. Pyrite
Pyrite
Pyrite (fools gold) is used in the manufacture of sulfur, sulfuric acid, and sulfur dioxide; pellets of pressed pyrite dust are used to recover iron, gold, copper, cobalt, and nickel.

Quartz
Quartz
Quartz crystals are popular as a semiprecious gemstone; crystalline varieties include amethyst, citrine, rose quartz, and smoky quartz. Because of its piezoelectric properties (the ability to generate electricity under mechanical stress), quartz is used for pressure gauges, oscillators, resonators, and wave stabilizers. Quartz is also used in the manufacture of glass, paints, abrasives, refractories, and precision instruments. Sandstone
Sandstone
Sandstone is used as a building stone, road bases and coverings, construction fill, concrete, railroad ballast, and snow and ice control.

Silica
Silica / Silicon
Silica is used in the manufacture of computer chips, glass and refractory materials, ceramics, abrasives, and water filtration; and is a component of hydraulic cements, a filler in cosmetics, pharmaceuticals, paper, and insecticides; as an anti-caking agent in foods; a flatting agent in paint, and as a thermal insulator. Silver
Silver
Silver is used in photography, chemistry, electrical and electronic products (because of its very high conductivity), fine silverware, electroplated wire, jewelry, coins, and brazing alloys and solders. Strontium
Strontium
Photoluminescent exit signs use a class of newly developed phosphorescent pigments that are based on strontium oxide aluminate chemistry.

Sulfur
Sulfur
Sulfur is of importance to every sector of the world's manufacturing processes, drugs, and fertilizer complexes. Sulfur is used as an industrial raw material through its major derivative, sulfuric acid. Sulfuric acid production is the major end use for sulfur. Most sulfur goes into fertilizer; oil refining is another major use as well as a source of sulfur.

Talc
Talc
The primary use for talc is in the production of paper. Ground talc is used as filler in ceramics, paint, paper, roofing, plastics, cosmetics, and in agriculture. Talc is found in many common household products, such as baby (talcum) powder, deodorant, and makeup. Very pure talc is used in fine arts and is called soapstone. It is often used to carve figurines. Tin
Tin
Tin is used in the manufacture of cans and containers, electrical equipment, and chemicals.

Titanium
Titanium
Titanium is a metal used mostly in jet engines, airframes, and space and missile applications. In powdered form, titanium is used as a white pigment for paints, paper, plastics, rubber, and other materials.
Trona
Trona is used in glass container manufacture, fiberglass, specialty glass, flat glass, liquid detergents, medicine, food additives, photography, cleaning and boiler compounds, and control of water pH. Trona is mined mainly in Wyoming. Tungsten
Tungsten
Tungsten is used in steel production, metalworking, cutting applications, construction electrical machinery and equipment, transportation equipment, light bulbs, carbide drilling equipment, heat and radiation shielding, textile dyes, enamels, paints, and for coloring glass. Uranium
Uranium
Uranium is a radioactive material used in nuclear defense systems and for nuclear generation of electricity. It also used in nuclear-medicine x-ray machines, atomic dating, and electronic instruments. Zeolites
Zeolites
Some of the uses of zeolite minerals include aquaculture (for removing ammonia from the water in fish hatcheries), water softener, catalysts, cat litter, odor control, and removing radioactive ions from nuclear-plant effluent. Zinc
Zinc
Zinc is used as protective coating on steel, as die casting, as an alloying metal with copper to make brass, and as chemical compounds in rubber and paint. Additional uses include galvanizing iron, electroplating, metal spraying, automotive parts, electrical fuses, anodes, dry-cell batteries, nutrition, chemicals, roof gutters, cable wrapping, and pennies. Zinc oxide is used in medicine, paints, vulcanizing rubber, and sun-block lotions. Zirconium
Zirconium
Zirconium is a metal recovered from zircon. "Zircon is used in mineral form in refractory products, where it is valued for its high melting temperature of 2,550°C. Some zircon is processed by chemical leaching to yield elemental zirconium. The best known use for zirconium metal is in nuclear reactors, where zirconium contains the fuel" (Kesler, 1994).

http://www.chemistryexplained.com/elements/L-P/Nickel.html

NICKEL


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Nickel

Overview

Nickel is the only element named after the devil. The name comes from the German word Kupfernickel, meaning "Old Nick's copper," a term used by German miners. They tried to remove copper from an ore that looked like copper ore, but they were unsuccessful. Instead of copper, they got slag, a useless mass of earthy material. The miners believed the devil ("Old Nick") was playing a trick on them. So they called the fake copper ore Old Nick's copper.
Since then, nickel has become a very valuable metal. The most common use is in the production of stainless steel, a strong material that does not rust easily. It is used in hundreds of industrial and consumer applications. Nickel is also used in the manufacture of many other alloys. An alloy is made by melting and mixing two or more metals. The mixture has properties different from those of the individual metals.
SYMBOL
Ni
ATOMIC NUMBER
28
ATOMIC MASS
58.69
FAMILY
Group 10 (VIIIB)
Transition metal
PRONUNCIATION
NI-kul
Nickel is classified as a transition metal. Transition metals are elements between Groups 2 (metals) and 13 (non-metals) in the periodic table. The periodic table is a chart that shows how chemical elements are related to one another. Nickel is closely related to iron, cobalt, copper, and zinc. These metals are close to nickel in the periodic table.

Discovery and naming

The study of metals was difficult for early chemists. Many metals looked very similar. They also acted very much like each other chemically. Nickel was one of the metals about which there was much confusion.

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Copper miners were confused about nickel and copper because they both occurred in ores with a green tint. But copper ores reacted differently to heat than did nickel ores. This confusion led to the choice for nickel's name.
But cobalt miners were confused too. Some ores of nickel also look like cobalt ores. But these ores did not react chemically in the same way either. Cobalt mine owners called the "misbehaving" ores of nickel "cobalt which had lost its soul."
Swedish mineralogist Axel Fredrik Cronstedt (1722-65) was the first person to realize that nickel was a new element. In 1751, he was given a new mineral from a cobalt mine near the town of Hälgsingland, Sweden. While Cronstedt thought the ore might contain cobalt or copper, his tests produced a surprising result. He found something in the mineral that did not act like cobalt, copper, or any other known element. Cronstedt announced that he had found a new element. He used a shortened version of Kupfernickel for the name of the new element. He called it nickel.

Physical properties

Nickel is a silvery-white metal. It has the shiny surface common to most metals and is both ductile and malleable. Ductile means capable of being drawn into thin wires. Malleable means capable of being hammered into thin sheets. Its melting point is 1,555°C (2,831°F) and its boiling point is about 2,835°C (5,135°F). The density of nickel is 8.90 grams per cubic centimeter.
Nickel is only one of three naturally occurring elements that is strongly magnetic. The other two are iron and cobalt. But nickel is less magnetic than either iron or cobalt.

Chemical properties

Nickel is a relatively unreactive element. At room temperature, it does not combine with oxygen or water or dissolve in most
Nickel samples.
Nickel samples.
acids. At higher temperatures, it becomes more active. For example, nickel burns in oxygen to form nickel oxide (NiO):
It also reacts with steam to give nickel oxide and hydrogen gas:

Occurrence in nature

Nickel makes up about 0.01 to 0.02 percent of the Earth's crust. It ranks about 22nd among the chemical elements in terms of abundance in the Earth's crust. Nickel is thought to be much more abundant in the Earth's core. In fact, many experts believe that the core consists almost entirely of iron and nickel.
One argument for this belief is the presence of nickel in meteorites. Meteorites are pieces of rock or metal from space that fall to the Earth's surface. Meteorites often contain a high percentage of nickel.
The most common ores of nickel include pentlandite, pyrrhotite, and garnierite. The element also occurs as an impurity in ores of iron, copper, cobalt, and other metals.
The United States' only nickel mine is located in Riddle, Oregon. In 1996, the mine produced 15,070 tons of nickel. By comparison, Russia produced 230,000 tons of nickel in the same year. Russia is the world's largest producer of nickel Other major nickel producers are Canada (183,059 tons in 1996), New Caledonia (142,200 tons), Australia (113,134 tons), and Indonesia (90,000 tons).
The largest single deposit of nickel is located at Sudbury Basin, Ontario, Canada. The deposit was discovered in 1883. It covers an area 27 kilometers (17 miles) wide and 59 kilometers (37 miles) long. Some experts believe the deposit was created when a meteorite struck the earth at Sudbury Basin.

Isotopes

There are five naturally occurring isotopes of nickel: nickel-58, nickel-60, nickel-61, nickel-62, and nickel-64. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope.
Seven radioactive isotopes of nickel are known also. A radioactive isotope is one that breaks apart and gives off some form of radiation. Radioactive isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive.
One radioactive isotope of nickel has limited use in industry, nickel-63. This isotope has two uses: for the detection of explosives, and in certain kinds of electronic devices, such as surge protectors. A surge protector is a device that protects sensitive electronic equipment like computers from sudden changes in the electric current flowing into them.

Extraction

The method used for making pure nickel metal is a common one in metallurgy. Metallurgy is the art and science of working with metals. Most nickel ores contain nickel sulfide (NiS). These ores are "roasted" (heated in air). Roasting converts the nickel sulfide to nickel oxide:

Ocean Song, by John T. Scott. This sculpture, located in New 
Orleans, Louisiana, is an example of an artistic use of stainless 
steel.
Ocean Song, by John T. Scott. This sculpture, located in New Orleans, Louisiana, is an example of an artistic use of stainless steel.

The nickel oxide is then treated with a chemical that will remove the oxygen from the nickel. For example:

A large amount of nickel is now recycled from scrap metal. Scrap metal comes from old cars, demolition of buildings, appliances like washing machines and stoves, and landfills. The task in recycling scrap metal is to find a way to separate
Nickel-cadmium batteries are used in laptop computers.
Nickel-cadmium batteries are used in laptop computers.
the nickel from other metals in the scrap. This can be done by taking advantage of special properties of nickel. For example, a magnet will remove nickel from scrap, leaving copper behind.

Uses

The most important use of nickel is in making alloys. About 80 percent of all nickel produced in the United States in 1996 was used to make alloys. About two-thirds of that amount went into stainless steel. Stainless steel is common to household appliances (like coffee makers, toasters, and pots and pans), kitchen sink tops and stoves, and medical equipment (X-ray machines, for example). It is also used to make heavy machinery and large containers in which large-scale chemical reactions are carried out. Artists sometimes use stainless steel in sculpture because it does not rust easily. Stainless steel is important to the food and beverage, petroleum, chemical, pharmaceutical (drug), pulp and paper, and textile industries.
Nickel is also used to make the superalloys used in jet engine parts and gas turbines. Superalloys are made primarily of iron, cobalt, or nickel. They also include small amounts of other metals, such as chromium, tungsten, aluminum, and titanium. Superalloys are resistant to corrosion (rusting) and retain their properties at high temperatures.
Nickel is also very popular in the manufacture of batteries. Nickel-cadmium (nicad) and nickel-metal hydride batteries are the most popular of these batteries. They are used in a great variety of appliances, including hand-held power tools, compact disc players, pocket recorders, camcorders, cordless and cellular telephones, scanner radios, and laptop computers.
Nickel is also used in electroplating, a process by which a thin layer of one metal is laid down on top of a second metal.

Electroplating with nickel

N ickel is commonly used in electroplating. Electroplating is the process by which a thin layer of one metal is laid down on top of a second metal. Here is how electroplating is done.
First, the nickel compound to be laid down is dissolved in water. The solution may be nickel chloride (NiCl 2 ), nickel nitrate (Ni(NO 3 ) 2 ), or some other nickel compound.
Second, a sheet of the metal to be electroplated is placed into the solution. Suppose the metal is steel. The steel sheet is suspended in the nickel chloride, nickel nitrate, or other nickel solution.
Third, an electric current is passed through the solution. The current causes nickel to come out of the solution. The nickel is then deposited on the surface of the steel. The longer the current runs, the more nickel is laid down. The thickness of the nickel layer can be controlled by the time the electric current runs through the solution.
Electroplating is used to make metal products with very specific qualities. Steel is strong but tends to corrode easily. Nickel does not corrode as fast as steel. A thin layer of nickel on top of steel protects the steel from corrosion.

Compounds

Some nickel compounds have important uses also. Many of these compounds are used in electroplating. Some are used to make alloys of nickel. Other nickel compounds are used as coloring agents. For example, the compound nickel dimethylglyoxime (C 8 H 14 N 4 NiO 4 ) is used as a coloring agent in paints, cosmetics, and certain kinds of plastics.
Other nickel compounds have somewhat more unusual uses. For example, the compound nickel dibutyldithiocarbamate (Ni[CS 2 N(C 4 H 4 ) 2 ] 2 ) is used as an antioxidant in tires. The rubber in tires reacts with oxygen in the air. When it does so, the rubber gets hard and stiff. The tires begin to break down. An additive like nickel dibutyldithiocarbamate can reduce the rate at which this process occurs. The life of tires is extended.

Health effects

Nickel can pose a health hazard to certain individuals. The most common health problem is called nickel allergy. Some people are more likely to develop nickel allergy than are others. People who are sensitive to nickel may develop a skin rash somewhat like poison ivy. The rash becomes itchy and may form watery blisters. Once a person gets nickel allergy, it remains with him or her forever.
Nickel is present in dozens of products. So it is easy for sensitive people to develop nickel allergy. Perhaps the most common cause of nickel allergy is body piercing. Some people have their ears pierced for earrings, while others have their lips, nose, or other body parts pierced. Inexpensive jewelry placed into these piercings is frequently made of stainless steel. Stainless steel contains nickel. The presence of nickel in a piercing can cause nickel allergy to develop.
Nickel can cause more serious health problems too. For example, people who are exposed to nickel fumes (dust and gas) breathe in nickel on a regular basis. Long term nickel exposure may cause serious health problems, including cancer.

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Read more: http://www.chemistryexplained.com/elements/L-P/Nickel.html#ixzz1ad7zn2w3             Copyright © 2011 Advameg, Inc.

Minggu, 19 Juni 2011

Mengapa bumi itu bundar?

apakah benar bumi itu bundar
nemesis nemesis
Jawaban Terbaik - Dipilih oleh Suara Terbanyak
Bundar adalah salah satu bentuk untuk benda 2 dimensi. Bumi bukan benda 2 dimensi, melainkan 3 dimensi, jadi bentuk bumi tidak bundar. Mungkin maksudmu bulat?

Bentuk bumi sendiri tidak benar2 bulat seperti bola, tapi lebih mirip sebuah telur (kembung di tengah dan agak pepat di ujung2nya). Kalau istilah ilmiahnya: bentuk bumi adalah elipsoida (bentuk 3 dimensi dari elips atau oval atau lonjong).

Kalau ditanya mengapa bumi berbentuk elipsoida, pastinya tidak ada orang yang tahu persis mengapa. Itu mungkin pertanyaan untuk Sang Pencipta. Ada sih teori yang mengatakan bahwa asal muasal terbentuknya bumi adalah dari gas fluid yang kemudian saling berkohesi (mengikat) sehingga secara alamiah membentuk gumpalan seperti bola (tapi bukan benar2 bulat seperti bola).

Tapi yang pasti, manusia sendiri berusaha untuk membuktikan seperti apakah bentuk bumi. Karena pada zaman Yunani Kuno, orang-2 percaya bahwa bentuk bumi adalah datar. Bahkan orang2 dulu juga percaya bahwa bumi adalah pusat peredaran tata surya. Namun semakin maju peradaban, semakin banyak bukti ilmiah bahwa bentuk bumi adalah elipsoida, terlihat dari panjangnya jari2 bumi di bagian katulistiwa (jari2 ekuatorial) yang lebih panjang daripada jari2 bumi di bagian kutub (jari2 polar).
materi referensi:
http://id.wikipedia.org/wiki/Bumi

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