Discharge tubes

Used (particularly He, Ar) to provide an inert atmosphere, e.g. for welding, and in electric light bulbs, valves and discharge tubes (particularly Ne). Liquid He is used in cryoscopy. The amounts of He and Ar formed in minerals by radioactive decay can be used to determine the age of the specimen. Xe and to a lesser extent Kr and Rn have a chemistry the other noble gases do not form chemical compounds. 

In a vacuum discharge tube, neon glows reddish orange. 

If photons of light of a suitable wavelength (usually ultraviolet or x-rays) impinge on a metal surface, electrons are emitted. This effect is photoelectric (or photovoltaic) and can be used to start a flow of electrons in a discharge tube. 

By use of a piezoelectric device, as in a gas lighter, a small spark containing electrons and ions can be produced. If the spark is introduced into the gas in a discharge tube, it will provide the extra initial electrons and ions needed to start a continuous discharge. A plasma torch is frequently lit (started) in this fashion. 

Other Arsenic Hydrides. Diarsine [15942-63-9] AS2H4, occurs as a by-product in the preparation of arsine by treatment of a magnesium aluminum arsenide alloy with dilute sulfuric acid and also may be prepared by passing arsine at low pressure through an ozonizer-type discharge tube (19). Diarsine is fairly stable as a gas but quite unstable (above — 100°C) in condensed phases. The for diarsine is +117 4 kJ/mol (28 1 kcal/mol) and... 

D. s-Aaetyl-2(3B)-oxaaolone. The crude mixture of 3-acety1 4- and 5-chloro-2-oxazolidinone from Step C is placed in a 2-L, three-necked flask equipped with a thermometer, sealed mechanical stirrer, and gas discharge tube. The material is heated to 120°C with stirring, and the temperature is then slowly increased to 150 C and held there until the evolution of gas ceases (Note 10). The cooled, black reaction mixture is distilled at 20 nm. The fractions boiling up to 150°C are collected and redistilled through a 50-cm X 3-cm Vigreux column fitted with a variable take-off head. There is obtained 140-172 g (55-68%) of product, bp 108-112°C (24 mm), which solidifies, rap 35-37°C (Note 11). 

AbfuhningS gang, kanal, m. excretory passage or duct efferent duct, -rohr, n. discharge tube or pipe. 

Fig. 14-4. An electric discharge tube, very low pressure. Electrons travel from the negative electrode to the positive electrode some of them pass through the triangular hole to produce a triangular spot on the fluorescent screen.

Fig. 14-5. An electric discharge tube with deflection electrodes.

Fig. 15-1. The spectrum of light emitted by a hydrogen discharge tube.

Hydrogen discharge Tube emiTs 1 tghT crt special frequencies only... 

Fig. 15-2. Contrast between the continuous spectrum of a hot tungsten ribbon and the line spectrum of a hydrogen discharge tube.

Disaccharides, 424 Discharge tube, 239, 255 Disproportionation, 361 Dissociation, 179 constant of HF, 361 Dissolving rate, 164 Distillation, 70 Disulfur dichloride, 103 Divalent, 282... 

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