Sorption balance

The most simple model uses the gas-phase concentration of the monomer as driving force. Alternatively, if capillary condensation of monomers is to be taken into account, the monomer concentration can be calculated directly from the liquid density. A sorption balance, for example, should be used to measure the constants of Equations (5.4-7) and (5.4-8), because of their dependence on the changing polymer structure formed in the polymerization process. 

There are many examples of second-order analyzers that are used in analytical chemistry including many hyphenated spectroscopic tools such as FTIR-TGA, IR-microscopy, as well as GC-MS, or even two-dimensional spectroscopic techniques. Another hyphenated technique that is being developed for the study of solid-state transitions in crystalline materials is dynamic vapor sorption coupled with NIR spectroscopy (DVS-NIR).26 DVS is a water sorption balance by which the weight of a sample is carefully monitored during exposure to defined temperature and humidity. It can be used to study the stability of materials, and in this case has been used to induce solid-state transitions in anhydrous theophylline. By interfacing an NIR spectrometer with a fiber-optic probe to the DVS, the transitions of the theophylline can be monitored spectroscopically. The DVS-NIR has proven to be a useful tool in the study of the solid-state transitions of theophylline. It has been used to identify a transition that exists in the conversion of the anhydrous form to the hydrate during the course of water sorption. 

The weight of gas adsorbed is sometimes measured, and for this purpose various kinds of microbalance have been used. McBain s sorption balance consists of a delicate helical quartz spring,5 suspending the adsorbing solid the upper end of the spring is fixed, and the lower end observed with a cathetometer. Bradley6 has used a balance with a beam, supported in the centre by a fine horizontal quartz fibre and references to other types of balance are given by McBain.7... 

The experiments are conducted with the help of the sorption balance shown in Figure 1. The sorption balance operates according to the principle developed and described by Losch et al. [3]. 

The main porous structure characteristics (Table 2) were determined on the basis of benzene vapor adsorption isotherms using McBain-Baker sorption balances at 20°C (293 K), i.e., the specific BET surface area (5bht) [39], the surface area of mesopores (5 ,e), and the parameters of the Dubinin-Radushkevich equation (the volumes of the micropores and supermicropores. Woi and W 2, and the characteristic energies of adsorption, E, and o ) 136,37). In addition, the total micropore volume (ZVT, ) and geometric micropore surface area (5J 1168] were calcu-... 

Changes in the structure and hydrophilic properties of the wood cell wall m specimens after the impregnation and ageing procedures samples were studied by the water vapours sorption method. The sorption-desoqjtion isotherms measured on a vacuum sorption balance at 295 K were analysed by the comparative method in combination with the BET method (8). The accessible specific area A (m /g), reflecting swelling capacity, the mass hydrophilicity a (mM/g) and the surface concentration of Ihc hydrophilic centres a (groups/nm ) was determined. 

The design of drying processes is strongly dependent on experiments. The fundamental investigation is the study of the sorption isotherm in a sorption balance. The result... 

The sorption (adsorption or desorption) rate is measured with a sorption balance (spring or electrical) whereas the solid sample is kept in a controlled environment. Assuming negligible surface resistance to mass transfer, the method is based on Pick s diffusion equation. 

Figure 14.13 Principle of a magnetic sorption balance (left conventional apparatus right magnetic suspension balance).

Table l.l Relative humidities at which cement constituents start to take up water vapour, measured on a sorption balance at 20°C using the ramp mode ... 

Dubina, E., L. Wadso and J. Plank (2011). A sorption balance study of water vapour sorption on anhydrous cement minerals and cement constituents . Cement and Concrete Research 41(11) 1196—1204. 

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