Effect of Silica Flour in Dow Corning High Vacuum Grease on Gas Chromatographic Retention Volumes

1961 ◽  
Vol 33 (11) ◽  
pp. 1625-1626 ◽  
Author(s):  
E. D. Smith
Keyword(s):  
High Vacuum ◽  
Chromatographic Retention ◽  
Retention Volumes

ADSORPTIVE AND GAS CHROMATOGRAPHIC PROPERTIES OF VARIOUS CATIONIC FORMS OF ZEOLITE X

1964 ◽  
Vol 42 (10) ◽  
pp. 2340-2350 ◽  
Author(s):  
H. W. Habgood
Keyword(s):  
Ionic Radius ◽  
Adsorption Process ◽  
Divalent Cations ◽  
Chromatographic Retention ◽  
Monovalent Cations ◽  
Zeolite X ◽  
Heats Of Adsorption ◽  
Quadrupole Interactions ◽  
Silver Compound ◽  
Retention Volumes

Gas chromatographic retention volumes for O2, N2, CH4, C2H6, C3H8, C4H10, C2H4, and C3H6 have been measured over a range of temperatures between 25 and 400 °C, on columns of the following ion-exchanged forms of zeolite X: Li+, Na+, K+, Mg++, Ca++, Ba++, and Ag+. In addition, for AgX zeolite, full isotherms have been determined for O2, N2, C2H6, and C2H4; and for NaX zeolite, isotherms for C2H6 and C2H4. The gas chromatographic retention volumes agree well with the isotherms in the case of NaX but are significantly low for AgX, presumably as the result of at least a portion of the adsorption process being slow. The heats of adsorption on NaX agree well with literature values for O2, N2, CH4, and C2H6 but are low for C3H8 and C4H10; further indication of slow processes and hence of a limitation of the g.c. technique. The observations can be correlated qualitatively in terms of the interplay of the following effects: (a) cationic field increases with decreasing ionic radius; (b) shielding of smaller cations is greater—at least in the six-membered oxygen-ring sites; (c) divalent cations, while having greater fields, are only half the number of monovalent cations and tend to be found in less exposed sites; and (d) the polarizing power of silver ion, which also occupies all types of exposed sites, is very strong. The most intense interactions were found with AgX; with ethylene a much stronger complex is formed than has been reported for any other silver compound. The significance of molecular quadrupole interactions on these heteroionic surfaces is shown by the much weaker cationic effects observed with O2 (which has negligible quadrupole moment) than with nitrogen.

Effect of the polymer glass transition on the chromatographic retention volumes

2005 ◽  
Vol 97 (3) ◽  
pp. 793-796
Author(s):  
J. S. Vrentas ◽  
C. M. Vrentas
Keyword(s):  
Glass Transition ◽  
Chromatographic Retention ◽  
Polymer Glass ◽  
Retention Volumes

Tests of the Consistency between Binary Gas Adsorption Isotherms and Binary Chromatographic Retention Volumes

2000 ◽  
Vol 39 (5) ◽  
pp. 1514-1519 ◽  
Author(s):  
Mark J. Heslop ◽  
Bryan A. Buffham ◽  
Geoffrey Mason
Keyword(s):  
Adsorption Isotherms ◽  
Gas Adsorption ◽  
Chromatographic Retention ◽  
Retention Volumes

Surface adsorption at low coverage of n-alkanes on bleached kraft papers using gas chromatography

1987 ◽  
Vol 65 (8) ◽  
pp. 1935-1939 ◽  
Author(s):  
N. Gurnagul ◽  
D. G. Gray
Keyword(s):  
Gas Chromatography ◽  
Free Energy ◽  
Surface Coverage ◽  
Surface Adsorption ◽  
Standard Free Energy ◽  
Chromatographic Retention ◽  
Heats Of Adsorption ◽  
Retention Volumes ◽  
Low Coverage ◽  
Entropy Of Adsorption

The adsorption at low surface coverage of a series of n-alkanes on various bleached kraft paper surfaces was measured by gas chromatography. Differences in surface area of the paper samples were readily measured from the gas chromatographic retention volumes. The standard free energy, the enthalpy, and the entropy of adsorption varied linearly with the number of carbon atoms in the n-alkanes. The heats of adsorption were close to the heats of liquefaction, indicating the non-specific interactions of the hydrocarbons with the bleached kraft surfaces. The London component of the surface free energy was estimated from the gas chromatographic results to be 47.9 mN/m.

A GAS CHROMATOGRAPHIC STUDY OF THE ADSORPTIVE PROPERTIES OF A SERIES OF ACTIVATED CHARCOALS

1959 ◽  
Vol 37 (5) ◽  
pp. 843-855 ◽  
Author(s):  
Henry W. Habgood ◽  
James F. Hanlan
Keyword(s):  
Gas Flow ◽  
Initial Slope ◽  
Chromatographic Retention ◽  
Chromatographic Study ◽  
Apparent Diffusion Coefficients ◽  
Apparent Diffusion ◽  
Retention Volumes ◽  
Carrier Gas Flow ◽  
Different Gases ◽  
Initial Heat

From measurements of the gas chromatographic retention volumes, the initial slopes of the adsorption isotherms of nitrogen and the simpler hydrocarbons on a series of steam-activated coconut charcoals were determined. The initial heats of adsorption were obtained in the usual way from the temperature dependence. It was found for all gases that both the initial slope of the isotherm and the initial heat of adsorption decreased with increasing degree of activation of the charcoal (i.e. with increasing surface area per g). This suggests that the higher affinity for the very small pores in less activated material more than counterbalances the lower total surface.Measurements at several different carrier gas flow rates of the relative band width for the charcoals of least and of greatest activation demonstrated, as might be expected, a greater resistance to mass transfer for the former. However, the apparent diffusion coefficients calculated on the assumption that all transport is by gas phase in the pores were nearly the same for each charcoal and showed relatively little variation among the different gases.

Replication of Wet Objects and Cells

1974 ◽  
Vol 32 ◽  
pp. 102-103
Author(s):  
S. Basu ◽  
D. F. Parsons
Keyword(s):  
Water Vapor Pressure ◽  
High Vacuum ◽  
Polystyrene Latex ◽  
Vacuum System ◽  
Saturated Water Vapor ◽  
Replication Method ◽  
New Methods ◽  
Saturated Water ◽  
Water Vapors ◽  
Intermediate Chamber

We are approaching the invasiveness of cancer cells from the studies of their wet surface morphology which should distinguish them from their normal counterparts. In this report attempts have been made to provide physical basis and background work to a wet replication method with a differentially pumped hydration chamber (Fig. 1) (1,2), to apply this knowledge for obtaining replica of some specimens of known features (e.g. polystyrene latex) and finally to realize more specific problems and to improvize new methods and instrumentation for their rectification. In principle, the evaporant molecules penetrate through a pair of apertures (250, 350μ), through water vapors and is, then, deposited on the specimen. An intermediate chamber between the apertures is pumped independently of the high vacuum system. The size of the apertures is sufficiently small so that full saturated water vapor pressure is maintained near the specimen.

Thin Pyrolytic Graphite Films for Electron Microscope Substrates

1971 ◽  
Vol 29 ◽  
pp. 226-227 ◽  
Author(s):  
George H. N. Riddle ◽  
Benjamin M. Siegel
Keyword(s):  
Vacuum Chamber ◽  
Pyrolytic Graphite ◽  
High Vacuum ◽  
Dark Field ◽  
Ultra High Vacuum ◽  
Graphite Substrate ◽  
Nickel Substrate ◽  
Routine Procedure ◽  
Field Electron Microscopy ◽  
Dark Field Electron

A routine procedure for growing very thin graphite substrate films has been developed. The films are grown pyrolytically in an ultra-high vacuum chamber by exposing (111) epitaxial nickel films to carbon monoxide gas. The nickel serves as a catalyst for the disproportionation of CO through the reaction 2C0 → C + CO2. The nickel catalyst is prepared by evaporation onto artificial mica at 400°C and annealing for 1/2 hour at 600°C in vacuum. Exposure of the annealed nickel to 1 torr CO for 3 hours at 500°C results in the growth of very thin continuous graphite films. The graphite is stripped from its nickel substrate in acid and mounted on holey formvar support films for use as specimen substrates.The graphite films, self-supporting over formvar holes up to five microns in diameter, have been studied by bright and dark field electron microscopy, by electron diffraction, and have been shadowed to reveal their topography and thickness. The films consist of individual crystallites typically a micron across with their basal planes parallel to the surface but oriented in different, apparently random directions about the normal to the basal plane.

A High Voltage Electron Microscopy Study of Sub-Oxide Formation in Vanadium

1971 ◽  
Vol 29 ◽  
pp. 212-213
Author(s):  
R. H. Geiss ◽  
R. L. Ladd ◽  
K. R. Lawless
Keyword(s):  
High Vacuum ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Ultra High Vacuum ◽  
Pure Oxygen ◽  
Pressure Oxidation ◽  
High Voltage Electron Microscopy ◽  
Oxidation Study ◽  
Voltage Electron ◽  
Good Agreement

Detailed electron microscope and diffraction studies of the sub-oxides of vanadium have been reported by Cambini and co-workers, and an oxidation study, possibly complicated by carbon and/or nitrogen, has been published by Edington and Smallman. The results reported by these different authors are not in good agreement. For this study, high purity polycrystalline vanadium samples were electrochemically thinned in a dual jet polisher using a solution of 20% H2SO4, 80% CH3OH, and then oxidized in an ion-pumped ultra-high vacuum reactor system using spectroscopically pure oxygen. Samples were oxidized at 350°C and 100μ oxygen pressure for periods of 30,60,90 and 160 minutes. Since our primary interest is in the mechanism of the low pressure oxidation process, the oxidized samples were cooled rapidly and not homogenized. The specimens were then examined in the HVEM at voltages up to 500 kV, the higher voltages being necessary to examine thick sections for which the oxidation behavior was more characteristic of the bulk.

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