Argon Separation

Oxygen heterocyclics, 10 567 Oxygen-hydrogen mixtures, 13 770-771 Oxygen impurities, in argon separation,... 

There has been interest in the low radiative background, low quenching argon-hydrogen diffusion flame. The temperature of this flame is too low to prevent severe chemical interferences and therefore the argon-separated air-acetylene flame has been most widely used. The hot nitrous oxide-acetylene flame (argon separated) has been used where atomization requirements make it essential. In all cases, circular flames, sometimes with mirrors around them, offer the preferred geometry. 

FIGURE 10 Air-separation plant with auxiliary argon separation column. 

There are two basic types of argon-purification subsystems in industrial use (1) the catalytic-combustion system as shown in Fig. 6.32 and (2) the adsorption system. The first subsystem adds hydrogen to the argon stream removed from the crude argon separation column. This mixture is compressed to 0.5 MPa and the oxygen is removed by combustion or combination with the hydrogen in a catalytic-combustion furnace. This results in an argon... 

A schematic illustration of a typical inlet apparatus for separating volatile hydrides from the analyte solution, in which they are generated upon reduction with sodium tetrahydroborate. When the mixed analyte solution containing volatile hydrides enters the main part of the gas/liquid separator, the volatiles are released and mix with argon sweep and makeup gas, with which they are transported to the center of the plasma. The unwanted analyte solution drains from the end of the gas/liquid separator. The actual construction details of these gas/liquid separators can vary considerably, but all serve the same purpose. In some of them, there can be an intermediate stage for removal of air and hydrogen from the hydrides before the latter are sent to the plasma. 

Alternatively, ions of any one selected m/z value can be chosen by holding the magnetic field steady at the correct strength required to pass only the desired ions any other ions are lost to the walls of the instrument. The selected ions pass through the gas cell and are detected in the singlepoint ion collector. If there is a pressure of a neutral gas such as argon or helium in the gas cell, then ion-molecule collisions occur, with decomposition of some of the selected incident ions. This is the MS/MS mode. However, without the orthogonal TOF section, since there is no further separation by m/z value, the new ions produced in the gas cell would not be separated into individual m/z values before they reached the detector. Before the MS/MS mode can be used, the instrument must be operated in its hybrid state, as discussed below. 

The solid to be examined must be vaporized in some way. This vaporization can be done by using the heat of the plasma flame or, more usually, the solid is ablated separately and the resulting aerosol is mixed with argon gas and swept into the center of the flame. 

Commercially pure (< 99.997%) helium is shipped directiy from helium-purification plants located near the natural-gas supply to bulk users and secondary distribution points throughout the world. Commercially pure argon is produced at many large air-separation plants and is transported to bulk users up to several hundred kilometers away by tmck, by railcar, and occasionally by dedicated gas pipeline (see Pipelines). Normally, only cmde grades of neon, krypton, and xenon are produced at air-separation plants. These are shipped to a central purification faciUty from which the pure materials, as well as smaller quantities and special grades of helium and argon, are then distributed. Radon is not distributed commercially. 

The U.S. production of argon is summarized in Table 5. Because argon is a by-product of air separation, its production is ca 1% that of air feed. Total 1988 United States consumption of neon, krypton, and xenon was 36,400, 6,800, and 1,200 m, respectively (88). 

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