Sodium lamps

In recent years, concentrated phosphoric acids, which may contain as much as 70% to 75% P2O5 content, have become of great importance to agriculture and farm production. World-wide demand for fertilizers has caused record phosphate production. Phosphates are used in the production of special glasses, such as those used for sodium lamps. 

Lamp types (a) incandescent and tungsten-halogen lamp shapes (b) fluorescent and compact fluorescent lamp shapes (c) typical high-pressure sodium lamp (d) typical metal halide lamp. 

Electrical Niobium is finding growing use in components for high-pressure sodium lamps. 

To express optical rotations in a meaningful way so that comparisons can be made, we have to choose standard conditions. The specific rotation, [a ]D, of a compound is defined as the observed rotation when light of 589.6 nanometer (nm 1 nm = 10-9 m) wavelength is used with a sample pathlength / of 1 decimeter (dm 1 dm = 10 cm) and a sample concentration C of 1 g/mL. (Light of 589.6 nm, the so-called sodium d line, is the yellow light emitted from common sodium lamps.)... 

We wish to test a new type of ceramic tube to the AljOg tube normally used to fabricate high-pressure sodium lamps in order to eompare lamp qualities and life-time operation. Select a method which would produce the desired results and describe how this would be accomplished. Note that the ceramic tube requires both strength and a high melting point. 

In this relationship, a is the observed rotation, d is the path length, s is the concentration of the solution in g solute/mL solution, a is the concentration in g solute/g of solution, and p is the density of the solution. The most commonly used light source is the sodium lamp, which has X = 589 nm. Therefore, designations of a specific rotation are indicated by the use of symbols such as ( + )589-[Co(en)3]3 +. ... 

The first high-intensity sodium lamp was introduced in Europe in 1931. Figure 9.26 shows a schematic view of a sodium lamp it comprises a glass shell containing sodium vapour at low pressure, metal electrodes to generate a current, and neon gas. The pressure inside the tube is at a relatively low pressure of 30 Pa, so some of the sodium evaporates to become a vapour. The inner side of the lamp is coated with the remainder of the metallic sodium as a thin film. 

An electrode is positioned at either end of the tube, and a large voltage applied. When current first passes between the electrodes, the neon is ionized to form a plasma, and starts to glow (as above), which explains why a sodium lamp first emits a pink shade before it glows with its characteristic orange colour. 

Sodium lamps glow pink before orange because of the neon they hold, which kick starts the sodium emission process. 

The lamp above is more properly called a low-pressure sodium lamp. Such lamps are ideal for street and road illumination, but the monochromatic nature of the emission makes seeing in colour impossible. An adaptation which emits a range of colours is the high-pressure sodium-vapour lamp, which is similar to that described above but contains a mixture of mercury and sodium. Such lamps emit a whiter light and are useful for extra-bright lighting in places such as road intersections, car parks and sports stadia. 

Strip lighting in a classroom, hospital, business hall or kitchen is often called fluorescent lighting, although in fact it is a phosphorescent process, as above. Each bulb consists of a thin, hollow glass tube that is sealed at both ends. It contains gas such as helium, argon or krypton, and a drop of liquid mercury (about 0.5 mg of mercury per kilogram of lamp, or 0.5 parts per million). Like the neon and sodium lamps above, the pressure inside the tube is about 30 Pa, so the mercury evaporates to become a vapour. It is the mercury that yields the light, albeit indirectly. 

The refractive index is usually reported as n, where the tiny 25 is the temperature at which the measurement was taken, and the tiny capital D means we ve used light from a sodium lamp, specifically a single yellow frequency called the sodium D line. Fortunately, you don t have to use a sodium lamp if you have an Abbe refractometer. 

To select a specific wavelength because the refractive index varies with the wavelength. Also, the light source used in most commercial refractometers uses ordinary white light and not a sodium lamp. 

Spectroscopy is the study of the absorption and emission of radiation by matter. The most easily appreciated aspect of the absorption of radiation is the colour shown by substances that absorb radiation from the visible region of the spectrum. If radiation is absorbed from the red region of the spectrum, the transmitted or unabsorbed radiation will be from the blue region and the substance will show a blue colour. Similarly substances that emit radiation show a particular colour if the radiation is in the visible region of the spectrum. Sodium lamps, for instance, owe their characteristic orange-yellow light to the specific emission of sodium atoms at a wavelength of 589 nm. 

Figure 2.2 The emission spectra of different spectral lamps (a) a low-pressure sodium lamp (b) a low-pressure mercury lamp (c) a high-pressure sodium lamp (d) a high-pressure mercury lamp.

The specific rotation of a compound, designated as [aj, is defined as the observed rotation, a, when the sample path length Z is 1 dm, the sample concentration C is Ig/mL and light of 599.6 nm wavelength (the D line of a sodium lamp, which is the yellow light emitted from common sodium lamps) is used. 

This means that the D line of a sodium lamp (Z = 599.6 nm) was used for light, that a temperature of 25 °C was maintained and that a sample containing 1.00 g/mL of the optically active morphine, in a 1 dm tube, produced a rotation of 132° in an anti-clockwise direction. 

The flame produced from common salt or a sodium lamp is adjusted to give a maximum of light, the tube T being removed for the time being. 

The specific rotation is defined as [a] = (100 x A)/ (c x /), where A is the observed rotation in degrees, c is the concentration of the optically active substance in grams per 100 ml of solution, and l is the path length in decimeters of the solution through which the rotation is observed. Light from a sodium lamp (596 nm) is commonly used for the measurement. 

Does the blue glow from this mercury lamp correspond to a longer or shorter wavelength than the yellow glow from a sodium lamp ... 

For a particular compound the observed rotation depends on the concentration of the compound, the path length of the sample tube, and the wavelength of the light that is used. Often the yellow light produced by a sodium lamp, called the sodium D line (wavelength = 589 run), is used. The specific rotation, a constant characteristic of each... 

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