McBain water adsorption

The results indicate that both NH4,TMA-fl and NH.,K-L are de-aluminated upon fluorination. Strong supporting evidence comes from framework I. R. data where the shifts in band position to higher wave numbers are as much as 20 cm-1. However, there is no evidence of structure stabilization. Also McBain water adsorption data give no indication of surface hydrophobicity. Therefore, it is likely that structure defects are formed in these two zeolites as a result of dealumination and cause low thermal stability. 

To analyze the adsorptive characteristics, water adsorption-desorption on LiChrolut EN adsorbent was studied by an adsorption apparatus with a McBain-Bark quartz scale at room temperature. LiChrolut EN particles have nanopores at/ < 1 nm and narrow mesopores at 1 [Pg.610]

Water adsorption onto a set of samples was studied using an adsorption apparatus with a McBain-Bark quartz scale. After evacuation to 10 Torr for 1-2h, samples were heated at 613 K for 3-4h to a constant weight, then cooled to 293 0.2 K, and adsorption of water vapor was studied at pressure (p) varied in the 0.06-0.999 p/po range. The measurement accuracy was 1 x 10 mg with relative mean error < 5%. 

Two different adsorbents, activated carbon Norit R 0.8 Extra (Norit N.V., The Netherlands) and molecular sieve (type 4A, Merck), were used to study tert-butylbenzene, cyclohexane, and water vapour breakthrough dynamics. Structural parameters of the carbon adsorbent were calculated from benzene vapour adsorption-desorption isotherms measured gravimetrically at 293 K using a McBain-Bakr quartz microbalance, and nitrogen adsorption-desorption isotherms recorded at 77.4 K using a Micromeritics ASAP 2405N analyzer described in detail elsewhere.22,24 Activated carbon Norit has a cylindrical... 

Following crystallization, the solid was separated from the mother liquor by filtration, washed with distilled water, and air dried in an oven at 100 C to remove loosely bound water. Samples of the dried powder were sent routinely to the x-ray laboratory. The fact that we could obtain a strip chart recording of the x-ray powder pattern within 30 minutes was an important factor in the pace of our work. Adsorption evaluations were facilitated by use of multiple, quartz spring, McBain-Bakr balances connected in parallel. As many as 16 adsorbent samples could be evaluated simultaneously. 

In some cases (dyes, etc.) the adsorption of solute in the surface may be so great that a solid film may be formed. The surface tensions of solutions containing hybrid ions may be greater or less than that of water.3 The change of surface tension of a solution with time was found by McBain, Ford, and Mills to be very slow, many days being needed to attain the niaximum effect,... 

Influence of Acid Treatment. The presence of free alkali on the surface of glass and its influence on adsorption and allied phenomena are well known. McBain (17) pointed out the significance of acid treatment of glass vessels to remove the alkali in quantitative treatment of the phenomenon mentioned. The removal of surface alkali caused a marked change in the production of —Az (20). This last effect was studied in Siemens-type vessels, some of which were prewashed with chromic acid and boiling distilled water and dried under vacuum for 24 hours others were used as they were prepared from fresh glass. 

Direct experimental verification of the Gibbs adsorption equation in aqueous solutions is difficult, because physical separation of the monomolecular layer at the water surface is required to compare the concentration differences between the surface layer and the bulk solution. Several attempts have been made on this subject from 1910 to the present day, and although an exact fit has never been obtained, the results show a good agreement with the theory. McBain and co-workers used a suitable microtome to cut off a thin layer of approximately 50-100 4m from the surface of phenol, p-toluidine etc. solutions and verified the Gibbs equation within experimental error in 1932. Later, isotopically labeled solute molecules were employed for this purpose. Beta-emitter molecules, such as 3H, 14C and 35S have also been used and the radioactivity close to the surface measured. Since electrons only travel a short distance, the recorded radioactivity comes from the interface or very near the interface. 

Gibbs s adsorption equation was tested by W. C. McC. Lewis, F. W. Donnan and J. T. Barker, and (in a more satisfactory way) by J. W. McBain and C. W. Humphries and McBain and R. C. Swain,who confirmed it for an air-solution interface. Zawidzki found that the concentration of saponin in the foam of a solution was 1 26 to 1 33 times that in the bulk of the solution there can be no doubt that the concentration is actually greater in the surface layer of a solution than in the interior. Ramsden observed the formation of a solid film on the surface of some solutions and suspensions, and Metcalf the formation of a skin of peptone on a water surface. These phenomena are connected with Gibbs s theory. 

Water vapour adsorption and desorption isotherms were determined gravimetrically at 298 K with the aid of quartz spring balances of the McBain-Bakr type. Prior to measurement each of the microporous carbons was outgassed at 573 K, the other samples at 673 K, for 16 hours to a vacuum of < 10 torr. The adsorbents used in this study are listed in Table I they have all been employed in other related studies and their properties are described elsewhere (ref. 9). 

---