Argon temperature

Alternately, air condensed at liquid argon temperature contents of the trap swept by a carrier gas onto GC column for determination by FID or a mass spectrometer. 

The x-ray powder diffraction patterns of all the samples were recorded on a Siemens 12 automated diffraction system using Cu radiation. Argon adsorption isotherms were obtained at liquid argon temperatures using an Omnisorp 100 analyzer. Argon adsorption capacities and x-ray diffraction patterns were used to ascertain phase purity. 

Textural characterization. The nitrogen and argon isotherms were obtained at liquid nitrogen and liquid argon temperature by using a Micromeritics ASAP 2010 apparatus (static volumetric technique). Before determination of adsorption-desorption isotherms the samples ( 0.2 g) were outgassed for 16 h at 350 °C under vacuum. 

Fig. 3.10 Derivatogram of a polyester resin in argon Temperature rise 6°C/min sample size 200 mg... 

The cool-down time depends upon the gas and its pressure. We have cooled small exchangers to liquid-nitrogen temperatures and liquid-argon temperatures in less than 30 sec. We expect to cool down special exchangers in substantially less time. We have cooled our hydrogen—nitrogen cascade exchangers in 15 to 20 min. 

The oxygen concentration was monitored principally by hardness tests. Hardness is generally believed to be a better indicator of the extent of interstitial contamination than chemical analysis, which is subject to scatter and inaccuracy because of samphng difficulty. Bend tests (at room and liquid argon temperatures) and room-temperature Olsen cup formabihty tests were conducted to determine the hardness levels at which the materials embrittled. 

The column is swept continuously by a carrier gas such as helium, hydrogen, nitrogen or argon. The sample is injected into the head of the column where it is vaporized and picked up by the carrier gas. In packed columns, the injected volume is on the order of a microliter, whereas in a capillary column a flow divider (split) is installed at the head of the column and only a tiny fraction of the volume injected, about one per cent, is carried into the column. The different components migrate through the length of the column by a continuous succession of equilibria between the stationary and mobile phases. The components are held up by their attraction for the stationary phase and their vaporization temperatures. 

Fender B E F and Halsey G D Jr 1962 Second virial coefficients of argon, krypton and argon-krypton mixtures at low temperatures J. Chem. Phys. 36 1881... 

The energy released when the process under study takes place makes the calorimeter temperature T(c) change. In an adiabatically jacketed calorimeter, T(s) is also changed so that the difference between T(c) and T(s) remains minimal during the course of the experiment that is, in the best case, no energy exchange occurs between the calorimeter (unit) and the jacket. The themial conductivity of the space between the calorimeter and jacket must be as small as possible, which can be achieved by evacuation or by the addition of a gas of low themial conductivity, such as argon. 

Fig. 6.2 Radial distribution function determined from a lOOps molecular dynamics simulation of liquid argon at a temperature of 100K and a density of 1.396gcm. ...

Carbenes are too reactive to be isolated and stored but have been trapped m frozen argon for spectroscopic study at very low temperatures... 

A study of Table 1.1 reveals interesting features as to the mobility of the adsorbed atoms. Thus, for an argon atom on the (100) face, the easiest path from one preferred site S to the next is over the saddle point P, so that the energy barrier which must be surmounted is (1251 — 855) or 396 X 10 J/molecule. Since the mean thermal energy kT at 78 K is only 108 J/molecule, the argon molecule will have severely limited mobility at this temperature and will spend nearly all of its time in the close vicinity of site S its adsorption will be localized. On the other hand, for helium on the... 

As already mentioned, the choice of the supercooled liquid as reference state has been questioned by some workers who use the saturation vapour pressure of the solid, which is measured at the working temperature in the course of the isotherm determination. The effect of this alternative choice of p° on the value of a for argon adsorbed on a number of oxide samples, covering a wide range of surface areas, is clear from Table 2.11 the average value of is seen to be somewhat higher, i.e. 18 OA. ... 

At sufficiently low temperatures the isotherm of argon on high-energy surfaces tends to assume a step-like character (cf. p. 86). 

Fig. 2.22 Adsorption isotherms of argon on graphitized carbon black at a number of temperatures," plotted as fractional coverage 0 against relative pressure p/p°. (Courtesy Prenzlow and Halsey.)...

Fig. 2.24 Adsorption isotherms of argon at 78 K on Spheron-6 carbon black, heated to various temperatures indicated in °C on each isotherm. (After Polley, Schaeffer and Smith. )...

Fig. 4.4 Plot of the logarithm of the Langmuir quotient 0/p( - 0) against 0 for adsorption on H-chabasite at various temperatures." (a) Argon (h) carbon dioxide. (After Barrer and Davies.)...

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