Iridium was discovered in 1803 by the English chemist Smithson Tennant. It was identified from the residue of platinum ore which was dissolved in nitro-hydrochloric acid (also known as aqua regia). Platinum ores are still the main sources today of iridium. The precious metal is likewise obtained as a by-product of mining nickel.

Below are some of the properties of iridium.

General:

• Chemical Symbol: Ir

• Atomic Number: 77

• Category (as an element): Transition Metal

• Group/ Period/ Block (in the Periodic Table): 9/ 6/ d

• Atomic Weight: 192.217 g.mol-1

• Electron Configuration: [Xe] 4f14 5d7 6s2

Physical:

• Density (near room temperature): 22.56 g.cm-3

• Liquid Density (at melting point): 19 g.cm-3

• Melting Point: 2466°C, 4471°F, 2739°K

• Boiling Point: 4428°C, 8002°F, 4701°K

• Heat of Fusion: 41.12 kJ.mol-1

• Heat of Vaporization: 563 kJ.mol-1

Atomic:

• Oxidation States: -3, -1, 0, 1, 2, 3, 4, 5, 6

• Electronegativity: 2.20 (Pauling scale)

• Atomic Radius: 136 picometre

• Covalent Radius: 141±6 picometre

Because of its characteristic of being very brittle, pure iridium is quite difficult – almost impossible, in fact – to machine. Its primary use is as a hardening agent for platinum. High-temperature equipment, such as crucibles, are made from platinum-iridium alloys. Compass bearings, balances and fountain pen tips, on the other hand, are made from osmium-iridium alloys.

Again, iridium is the most corrosive resistant precious metal known. Coupled with its resistance to extremely high temperatures, this special characteristic makes iridium ideal for use in certain parts of aircraft engines. It is also alloyed with titanium to make deep-water pipes.

Other uses of iridium include the following:

1. Electrical contacts for spark plugs (due to its resistance to arc erosion);

2. Computer memory devices;

3. Direct-ignition engine (as a catalyst);

4. Radiotherapy (as a source of radiation);

5. X-ray telescopes.

In 2007, worldwide demand for iridium reached 3,701 kilograms (119,000 troy ounces). Distribution of these were as follows: electrochemical uses (1,100 kilograms); electrical uses (780 kilograms); for catalysis (750 kilograms); and other applications (1,100 kilograms).

Iridium is found at highest concentrations within the Earth’s crust in three specific types of geologic structures: in impact craters, in igneous deposits, and in deposits reworked from either of the first two. The Bushveld igneous complex in South Africa is the largest known primary reserves for iridium in the world. Other important sources of this precious metal are the Sudbury Basin in Canada and the nickel-copper-palladium deposits near Norilsk in Russia. Several smaller iridium reserves are also found in the United States.

Beginning the year 2000, the annual production of iridium is about 3 tonnes (96,500 troy ounces). Its price as of 2007 is 14,667 U.S. dollars per kilogram (440 U.S. dollars per troy ounce).

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On Orientation

There are a number of principles that you have to keep in mind to take advantage of passive solar energy fully. The applications will rely on the specific location and climate you belong to. Orientation refers to the positioning of the home so that you get most of the sun’s rays to heat and minimize the impact for cooling. Shading is vital in managing the natural light and temperature of the home.

Shade can be given by other structural elements. Insulation refers to keeping a warm home during the winter and a cool house during the summer. Thermal mass refers to heat storage during daytime and its release after the sun is gone. The windows will make sure that the home stays comfortable any day of the year. Ventilation refers to maintaining the cool inside the home during extra hot days.

Passive Solar Heating

Passive solar heating belongs to the category of solar space heating. The heating process can be done by orienting the home well so that most of the windows face to the south. The windows should be sized properly too, so that optimal heat gain will be attained. The home has to be insulated to reduce loss of heat. Passive cooling is a kind of solar cooling. The main idea behind passive cooling is to reduce the impact of the sun by orienting the landscape and the house so that you get the most benefits out of cool breezes.

The home also has to be designed to reduce barriers to air paths through the home to let natural ventilation in. You need to use the right type and size of windows to reduce the heat during extra hot days. Landscaping and structural features can be used to make shade. The home also has to be insulated well to keep the right temperature.

On Daylighting

Daylighting is a kind of solar energy lighting. It is described as the use of natural light to illuminate the house. Good daylighting provides the right light to all your rooms, while minimizing costs in utilities and electricity. You can daylight the house well by sizing and positioning the windows so that natural light freely enters the home. You should also use exterior shading that will diffuse the light.

Passive solar energy is considered as a natural and very cost-effective way to maintain your home. You can save so much in the long run and expect to have the right light and temperature inside your home for years to come. Talk to experts on how you can install the right elements.

Modern light fixtures