The metallic chemical elements collectively known as precious metals are called as such because of their extreme rarity and high economic value. Precious metals occur naturally or are by-products of the processing of other less rare metals.
In order of increasing mass abundance (parts per billion), the precious metals are rhenium, rhodium, iridium, ruthenium, osmium, gold, platinum, palladium, and silver. These metals are not radioactive and are mostly used for industrial purposes and for jewelry.
Still, precious metals have some safety issues attached to them:
Rhenium:
Since rhenium is used in very small amounts, its toxicity is virtually unknown. The hazardous property of rhenium halide, for example, may be attributed either to rhenium itself or to the other elements that make up the compound. Another rhenium compound – potassium perrhenate – is known to have a median lethal dose much like that of sodium chloride (commonly known as table salt).
Rhodium:
Although rhodium is inert (being a noble metal, as almost all the other precious metals are), it can be reactive, especially if used as compounds. In its basic form, however, rhodium is not known to cause any harm.
Iridium:
Iridium, when finely divided, can pose some hazards – it can ignite in air. Apart from this, accidental exposure to a radioisotope of iridium may cause poisoning by radiation, burns, and even death.
Ruthenium:
Three conditions may be associated with exposure to ruthenium: it can stain the skin; it may accumulate in bones; and it may increase the risk of cancer. Ruthenium tetroxide, a yellow, diamagnetic tetrahedral ruthenium compound, is highly toxic and volatile; it may explode if it comes into contact with combustible materials.
Osmium:
Osmium, like iridium, can ignite spontaneously in air when in finely divided form. The compound osmium tetroxide, in particular, is highly volatile and is extremely toxic if accidentally inhaled, ingested, or comes into contact with the skin.
Gold:
Gold, in its elemental form, does not cause irritation and is not toxic even when ingested. In fact, it is used as a component in some alcoholic drinks and as a food additive. However, ionic chemical compounds of gold (example, gold chloride) can be extremely harmful to the kidneys and liver.
Platinum:
Findings by the U.S. federal agency CDC reveal that exposure to platinum salts, on the short term, may cause nose, throat, and eye irritation. Long-term exposure to these compounds, on the other hand, may cause skin and respiratory allergies.
Palladium:
Palladium in bulk metallic form is completely inert. The same can’t be said though of the metal in finely divided form, which can readily ignite in air.
Silver:
Silver compounds (example, colloidal silver), when absorbed into the body, may cause argyria, a condition characterized by the bluish-gray pigmentation of the skin, mucous tissues, and the eyes. While the condition is not really harmful to one’s health, it is often permanent. Otherwise, silver per se is not at all toxic.
It certainly is important to know that each of the precious metals has possible health hazards so that first-time handlers can take the necessary precautions.
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In the periodic table of elements, rhenium is found as a third-row transition metal in group 7. Known to be one of the rarest precious metals in the Earth’s crust, rhenium has an average concentration of 1 part per billion. It is obtained mainly as a by-product of the refinement of two other chemical elements – copper and molybdenum.
Rhenium was discovered as a trace element in the mineral columbite and in platinum ores. Three German chemists – Otto Berg and the couple Walter Noddack and Ida Tacke – made the discovery in 1925. This find made rhenium the last identified naturally occurring precious metal with stable isotopes. Actually, naturally occurring rhenium is composed of 2 stable isotopes and 26 unstable ones.
Following is a list of some of the properties of rhenium:
General:
• Chemical Symbol: Re
• Atomic Number: 75
• Category (as an element): Transition Metal
• Group/ Period/ Block (in the Periodic Table): 7/ 6/ d
• Atomic Weight: 186.207 g.mol-1
• Electron Configuration: [Xe] 4f14 5d5 6s2
Physical:
• Density (near room temperature): 21.02 g.cm-3
• Liquid Density (at melting point): 18.9 g.cm-3
• Melting Point: 3186°C, 5767°F, 3459°K
• Boiling Point: 5596°C, 10105°F, 5869°K
• Heat of Fusion: 60.43 kJ.mol-1
• Heat of Vaporization: 704 kJ.mol-1
Atomic:
• Oxidation States: 7, 6, 5, 4, 3, 2, 1, 0, -1
• Electronegativity: 1.9 (Pauling scale)
• Atomic Radius: 137 picometre
• Covalent Radius: 151±7 picometre
• Ionization Energies: 760 kJ.mol-1 (first), 1260 kJ.mol-1 (second), 2510 kJ.mol-1 (third)
Rhenium is silvery-white in appearance. It is the third element (after tungsten and carbon) with the highest melting point and the fourth densest (after platinum, iridium, and osmium). Commercially, rhenium is traded in powder form. Its principal application is in the making of certain parts of jet engines. Here, the metal is added to high-temperature nickel-based superalloys.
Other uses of rhenium are as follows:
1. As catalysts in making lead-free, high-octane gasoline.
2. As filaments in making ion gauges, mass spectrographs, and photoflash lamps.
3. As electrical contact materials, due to its high resistance to arc corrosion and wear.
4. As catalysts for hydrogenation of fine chemicals, because of its high resistance to chemical poisoning from phosphorus, sulfur, and nitrogen.
5. As treatment for liver cancer, because of its radioactive isotopes.
Rhenium resources are identified in several countries, which include Chile, Peru, Armenia, Mexico, Russia, Canada, Kazakhstan, and Uzbekistan. The estimated total resource from these eight countries is 6,000 tonnes (6 million kilograms).
The United States alone, on the other hand, has an estimated total resource of 5,000 tonnes (5 million kilograms). These are identified in the states of Arizona, Miami, and Utah. But in spite of these significant resources, the U.S. continues to import a big part of its total consumption of the precious metal from some of the countries mentioned above.
Since rhenium and its compounds are used in very small amounts, very little is known about their toxicity. So far, only a few rhenium compounds have been tested for toxicity, and these include rhenium trichloride and potassium perrhenate.
The price of rhenium is about 250 U.S. dollars per troy ounce (about 8,300 U.S. dollars per kilogram).
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2012 is less than two years away, but for the past few years it has been spawning a wide range of 2012 doomsday theories. Below is a quick rundown of some of them.
• Geomagnetic reversal. Erroneously called polar shift, this involves the reversal of the earth’s magnetic field, with magnetic north becoming magnetic south and vice-versa.
• Nbiru Collision. Proponents of this theory claim that a large planetary object (variously refered to as Nbiru or Planet X) will collide with or narrowly miss Earth. This idea has actually been proposed for over a decade and was only recently linked with 2012 doomsday theories.
• Galactic alignment. In 2012, the sun, Earth and galactic equator will come into alignment, which may doomsday prophets believe will cause chaos on our world, possibly leading to mass extinctions.
More and more homes, offices and devices are now relying on solar power as people are becoming more aware of the potential dangers of other unnatural sources of power. It is important that you know more about the idea to determine if it is the best option for you. Solar power can render several benefits for the long term. You can take advantage of the features by choosing the right type and maximizing the effect right in your own home.
About Solar
Solar power is described as the creation of electricity straight from the sun. The generation can be direct with the use of PV or photovoltaics or indirect via CSP or concentrating solar power. CSP is done by using the energy of the sun to focus and boil water which will eventually create solar power. Solar power has the capacity to give more than 1000 times the total world energy consumption back in 2008. However, solar power only comprised 0.02% of the total in 2008.
If solar power will be used double every 2 to 3 years, it can become the dominate source of energy for the century. The biggest solar power plants, are concentrating solar thermal plants, although new multi-megawatt photovoltaic plants have also been created. More and more countries are investing in the bigger photovoltaic power stations, like Germany and Portugal.
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Terrestrial solar power is a predictable and intermittent source of energy, which means even though solar power is not readily available all the time, people can still predict it using a certain degree of accuracy when the energy source will or will not be available. A number of technologies, like the solar thermal concentrators, include an element of thermal storage, such as molten salts.
These come in the form of heat and are considered as store spare solar energy that can readily be made available overnight or at times when solar power is not available to create electricity. Orbital solar power collection also avoids the intermittent use, although satellite launching and beaming of the gathered power are required to get antennas on Earth. The enhanced intensity of the sunlight over the atmosphere also tends to boost the generation efficiency.
About Solar Energy
Solar energy, heat and radiant light that emanates from the sun have been controlled by humans beginning the ancient periods using a wide range of evolving technologies. Solar radiation, together with secondary solar-powered resources like biomass, wind, wave and hydroelectricity are accountable for majority of the available renewable energy on Earth. Only a small fraction of the available solar energy is utilized.
Solar powered electrical generation depends on photovoltaics and heat engines. The uses of solar energy are only limited by human ingenuity. Some of the other uses of solar energy include space cooling and heating via solar architecture, solar hot water, solar cooking, potable water via distillation and disinfection, daylighting and high temperature process heat for industrial functions. Solar panels are one of the most effective and basic ways to gather solar energy.
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