Electrical sparks

Other oxygen fluorides, O2F2, O4F2, O5F2 and 06p2, are prepared by passing an electric spark through a mixture of O2, F2 and sometimes O3. 

The focus of this section is the emission of ultraviolet and visible radiation following thermal or electrical excitation of atoms. Atomic emission spectroscopy has a long history. Qualitative applications based on the color of flames were used in the smelting of ores as early as 1550 and were more fully developed around 1830 with the observation of atomic spectra generated by flame emission and spark emission.Quantitative applications based on the atomic emission from electrical sparks were developed by Norman Lockyer (1836-1920) in the early 1870s, and quantitative applications based on flame emission were pioneered by IT. G. Lunde-gardh in 1930. Atomic emission based on emission from a plasma was introduced in 1964. 

Flame plating (D-gun) employs oxygen and fuel gas. In this method, developed by the Union Carbide Corporation, the gas mixture is detonated by an electric spark at four detonations per second. The powders, mixed with the gas, are fed under control into a chamber from which they are ejected when detonation occurs. The molten, 14—16-pm particles are sprayed at a velocity of 732 m/s at distances of 5.1—10.2 cm from the surface. The substrate is moved past the stationary gun. 

Dust explosions usually occur in pairs. The first explosion involves dust already in suspension. This jars dust from beams, ledges, etc, creating a second cloud to which the explosion propagates, resulting in a secondary explosion. Dust clouds have been ignited by open flames, electric sparks, hot... 

Emission spectroscopy is the analysis, usually for elemental composition, of the spectmm emitted by a sample at high temperature, or that has been excited by an electric spark or laser. The direct detection and spectroscopic analysis of ambient thermal emission, usually ia the iafrared or microwave regioas, without active excitatioa, is oftea termed radiometry. la emission methods the sigaal iateasity is directiy proportioaal to the amouat of analyte present. 

Hot surfaces and electric sparks are potential ignition sources for carbon disulfide. The ignition temperature depends on specific conditions, and values from 90 to 120°C in air have been reported (2,22). Data on carbon disulfide oxidation and combustion have been summarized (18). Oxidation products ate generally sulfur dioxide [7446-09-5] and carbon dioxide [124-58-9J ... 

The fundamental parameters in the two main methods of achieving ignition are basically the same. Recent advances in the field of combustion have been in the development of mathematical definitions for some of these parameters. For instance, consider the case of ignition achieved by means of an electric spark, where electrical energy released between electrodes results in the formation of a plasma in which the ionized gas acts as a conductor of electricity. The electrical energy Hberated by the spark is given by equation 2 (1), where V = the potential, V 7 = the current. A 0 = the spark duration, s and t = time, s. 

Thermal ignition sources A source that will cause the ignition of a flammable gas, vapor, or dust, such as an electric spark, flame, or hot surface. 

Schlag-versuch, m. impact test, percussion test, -wasser, n. bilge water, -welte, /. striking distance (of an electric spark), spark distance. -werk, n. striking appparatus, specif, rammer signal bell, -wetter, n. pi. fire damp. 

The key to safety in explosives manufacturing is to use isolated high-velocity nitric acid reactors that have only a veiy small hold up at any one time (that is, only a small amount of dangerous material is held up inside the reactor at any time). Units are widely spaced, so any accident involves only small amounts of explosive and does not propagate through the plant. Fire and electrical spark hazards are rigorously controlled, and manpower reduced to the absolute minimum through automation. 

Because combustion is normally initiated by an electric spark, the gasoline engine is also frequently known as a spark-ignition engine. 

Ignition can take place for any flammable mixture within the concentration ranges for the respective LEL and UEL. The conditions for ignition may vary with the specific mixture, the type of oxidant (usually air or pure oxygen), the temperature, and pressure of the system. Ignition may result from electrical spark, static spark, contact with hot surfaces (autoignition) (see Figures 7-48,... 

This chapter describes the basic principles and practice of emission spectroscopy using non-flame atomisation sources. [Details on flame emission spectroscopy (FES) are to be found in Chapter 21.] The first part of this chapter (Sections 20.2-20.6) is devoted to emission spectroscopy based on electric arc and electric spark sources and is often described as emission spectrography. The final part of the chapter (Sections 20.7-20.11) deals with emission spectroscopy based on plasma sources. 

Nitric oxide is the most stable oxide of nitrogen. It decomps above 1000° and will not support combustion below this temp. When mixed with hydrogen, it can be expld by a long duration, intense electric spark (Ref 8). It is very endothermic, its Qf being —21,575cal/g at RT (Ref 5)... 

Perhaps its most undesirable reaction is that with ozone N2O4+03 = N205+02, Under closed vessel conditions, using an electric spark, this reaction is explosive (Ref 33). However, when the reaction occurs in the atm, it proceeds at a slower rate, and effectively works to strip the UV shield of ozone surrounding the earth greatly increasing the possibility of skin cancer (Ref 40)... 

Ignition by Electric Sparks and Its Mechanism of Flame Formation. 26... 

The answer is "NO." In the combustible mixture, an electric spark produces a flame kernel. Initially, its shape is elliptical (like an American football), and then becomes a torus (like an American doughnut). Afterwards, it changes into almost spherical shape, and propagates spherically in the unbumed mixture. This process is formed by the existence of spark electrodes, which is necessary for spark discharge. Spark electrodes lead not only to heat loss from the flame kernel but also a change in the kernel shape. Both affect the minimum ignition energy. 

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