The product is further concentrated in another auxiliary rectification column before being vaporized and passed through a catalytic furnace to combine any remaining hydrocarbons with oxygen. To recover these rare gases, liquid oxygen from the reboiler of the upper column is first sent to an auxiliary condenser–boiler to increase the concentration of the krypton and xenon. Since the boiling points of krypton and xenon are higher than those of oxygen, these two components in atmospheric air tend to collect in the oxygen product of the double column. Thus, a very large amount of air has to be processed to produce an appreciable amount of these rare gases. The concentrations of krypton and xenon in atmospheric air are quite small. The resulting crude helium and neon are further purified by a series of charcoal adsorption units to provide high-purity neon. Recovery of these gases is accomplished by periodic venting of a small portion of the gas from the dome of the condenser and transfer to a small condenser–rectifier refrigerated with liquid nitrogen from the condenser of the double column. Since helium and neon have boiling points considerably below that of nitrogen, these gases will collect on the nitrogen side of the condenser–reboiler associated with the double-column air separation system. Air-separation plant with auxiliary argon separation column. Applications include phototherapy of the eye, pumping dye lasers, printing, and lithography.įIGURE 10. The excitation mechanisms for these lasers involve electron collisions first populating the ion ground states of the argon and krypton species, with subsequent electron excitation to the upper laser level. Some smaller, lower power versions of the argon ion laser are air cooled and offer lifetimes of 5000 hr. The high-power requirements, which put great demands on the strength of the laser discharge region, limit the lifetime of the high-power versions of these lasers. They are relatively inefficient and consequently require high-input power and water cooling for most units. The size of the laser tubes range from 50 to 200 cm in length, with a separate power supply. These lasers have the capability of producing more than 20 W of continuous power for the largest versions. They were the first lasers to operate in the green and blue regions of the spectrum, and some versions provide ultraviolet output. Silfvast, in Encyclopedia of Physical Science and Technology (Third Edition), 2003 VI.A.2 Argon and Krypton Ion LasersĪrgon and krypton ion lasers were discovered shortly after helium–neon lasers. Krypton difluoride is a powerful oxidizing agent and is capable of oxidizing and fluorinating xenon gas to XeF 6 and gold metal to AuF 5. No other molecular fluoride of krypton is known, so all krypton compounds are derived from KrF 2. Although the first krypton compound to be prepared was described as the tetrafluoride, the properties ascribed to this material have been shown to be those of the difluoride. The heat of atomization for KrF 2 is only 97.8 kJ mol −1 and is substantially less than that of F 2 (157.7 ± 0.4 kJ mol −1), making it a better low-temperature source of fluorine atoms and an aggressive fluorinating agent at even low temperatures. Consistent with its thermodynamic instability, krypton difluoride is a powerful oxidative fluorinating agent and is capable of oxidizing xenon to XeF 6 and gold to AuF 5. The standard enthalpy of formation (derived from calorimetric measurements of the gaseous compound at 93 ☌) is 60.2 kJ mol −1. The KrF 2 molecule has been shown, like XeF 2, to be linear in the gas phase, in the solid state, and in solution. It can, however, be stored for indefinite periods of time at −78 ☌. The simplest of these compounds is KrF 2, a colorless crystalline solid which can be sublimed under vacuum at 0 ☌ but is thermodynamically unstable and slowly decomposes to the elements at ambient temperatures. Krypton is the lightest of the noble gases that forms isolable chemical compounds in bulk amounts. Schrobilgen, in Encyclopedia of Physical Science and Technology (Third Edition), 2003 IV.A Krypton Difluoride Group 8A (or VIIIA) of the periodic table are the noble gases or inert gases: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).Gary J. Inert Gases position in Periodic TableĪnswer: Group 8A - The Noble or Inert Gases. It is a soft, silvery-white, highly reactive metal.Ħ. Acidic substances are usually identified by their sour taste.Īnswer: Sodium is a chemical element with the symbol Na (from Latin natrium) and atomic number 11. A base is a molecule or ion able to accept a hydrogen ion from an acid. Answer: An acid is any hydrogen-containing substance that is capable of donating a proton (hydrogen ion) to another substance.
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