Tungsten light bulb

The electrical uses of mercury include its application as a seal to exclude air when tungsten light bulb filaments are manufactured. Fluorescent light tubes and mercury arc lamps that are used for street lighting and as germicidal lamps also contain mercury. 

High-intensity radiation in the visible region of the spectrum is obtained from a simple tungsten light bulb. This bulb is essentially a black-body emitter and the relative intensity of the wavelengths of light emitted depends on the temperature of the tungsten wire as shown below. 

Scheme 11.4 illustrates some representative halogenation reactions. The reaction in Entry 1 was conducted by slow addition of bromine to excess 2-methylpentane at 60°C, with irradiation from a tungsten light bulb. The reaction in Entry 2 is a typical benzylic bromination, carried out at 125°C with irradiation from a sun lamp. Entries 3 and 4 are examples of NBS bromination using benzoyl peroxide as the initiator. Entry 3 is interesting in that none of the allylic isomer 2-bromo-3-heptene is found. Entries 5 and 6 are examples of chlorination by f-butyl hypochlorite in which the f-butoxy radical is the chain carrier. Note that in Entry 6, both the primary and secondary allylic products are formed. The reaction in Entry 7 uses sulfuryl chloride as the halogenation reagent. Note that in contrast to chlorination with CI2 (see p. 1021), the reaction shows selectivity for the benzylic position. 

A thermostatted water bath illuminated by 60-W Tungsten light bulbs (approximately 50-75 pmol photons m s ) for growth of liquid cultures. 

The same properties that make molybdenum metal effective in high temperature furnace appHcations make it useful as support wires for tungsten filaments in incandescent light bulbs and as targets in x-ray tubes. 

Real or gray bodies deviate from these ideal blackbody values by the A-dependent emissivity, but the color sequence remains essentially the same. This mechanism explains the color of incandescent light sources such as flames in a candle, tungsten filament light bulb, flash bulb, carbon arc, limelight, lightning in part, and the incandescent part of pyrotechnics (qv). 

It is widely used by the electronics industry in the manufacture of capacitors, where the oxide film is an efficient insulator, and as a filament or filament support. Indeed, it was for a while widely used to replace carbon as the filament in incandescent light bulbs but, by about 1911, was, itself superseded by tungsten. 

The term plastic is not a definitive one. Metals, for instance, are also permanently deformable and are therefore plastic. How else could roll aluminum be made into foil for kitchen use, or tungsten wire be drawn into a filament for an incandescent, light bulb, or a 100 ton ingot of steel be forged into a rotor for a generator. Likewise the different glasses, which contain compounds of metals and nonmetals, can be permanently shaped at high temperatures. These cousins to polymers and plastics are not considered plastics within the plastic industry or context of this book. 

Langmuir s research on how oxygen gas deteriorated the tungsten filaments of light bulbs led to a theory of adsorption that relates the surface concentration of a gas to its pressure above the surface (1915). This, together with Taylor s concept of active sites on the surface of a catalyst, enabled Hinshelwood in around 1927 to formulate the Langmuir-Hinshelwood kinetics that we still use today to describe catalytic reactions. Indeed, research in catalysis was synonymous with kinetic analysis... 

The lifetime of a tungsten filament in an incandescent light bulb depends a great deed on the grain size of the wire used to make the filament. W-metal powder is pressed into a bar at pressures which ensure that the density is as... 

Small amounts of thorium are used in alloys with tungsten to produce the spiral filaments of light bulbs. Higher temperature generate a brighter light. 

The dark spot on the inside of a burned-out light bulb is tungsten metal that has sublimed (vaporized from the solid) as a consequence of the heating of the tungsten filament to produce white light. 

Cooledge A process for forming tungsten powder into wire, important in the development of the electric light bulb. Developed in 1908. 

The second difference is the gas inside the bulb. Inside a normal light bulb, the gas is usually argon, but the gas inside the quartz halogen bulb is iodine vapour at low pressure, which has the ability to combine chemically with tungsten vapour. When the temperature is sufficiently high, the halogen... 

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