Piezometric method

Conventionally, molecular uptake is recorded gravi-metrically [18-20]. Alternatively, for a limited supply of adsorbate, molecular uptake may also be calculated from a knowledge of the time dependence of the pressure (piezometric method [21, 22]) or composition of the gas phase. Changing the sorbate pressure by a step change of the gas volume has proved to be a very efficient method for following fast sorption processes (single step method [23, 24]). The sorption uptake may also be measured volumctrically by mans of a gas burette arrangement [25]. 

Measurement of the transient adsorption or desorption curve for a sample of zeolite crystals exposed to a step change in ambient sorbate concentration (pressure) provides, in principle, a simple and direct method of measuring the intracrystalline diffusivity (D). Such measurements are conveniently carried out by gravimetric, volumetric or piezometric methods. The... 

Sorption Rates in Batch Systems. Direct measurement of the uptake rate by gravimetric, volumetric, or piezometric methods is widely used as a means of measuring intraparticle diffusivities. Diffusive transport within a particle may be represented by the Fickian diffusion equation, which, in spherical coordinates, takes the form... 

Brandani, S., Analysis of the Piezometric Method for the Stucfy of Diflusion in Microporous Solids Isothermal Case, Adsorption, 4, 17 (1998). 

Single-component equilibrium isotherms are commonly measured by gravimetric or piezometric methods (see Fig. 9). An alternative technique based... 

The piezometric method involves following the pressure response in a dosing cell connected to an uptake cell containing a sample of the adsorbent. According to the results reported in the hterature, the piezometric method can be used to accurately measure intracrystalline diffusivities for fast diffusing and strongly adsorbed species such as benzene on NaX [15,16]. Furthermore, it is also claimed to provide the required accuracy needed to study combined intracrystalline processes such as diffusion and first-order reaction [17]. 

The quality of approximation of the initial pvT data is high and the standard deviation 8z ranges from 0.09 to 0.2%. For data [3.66] obtained by the piezometric method, the deviation increased to 0.57%. The calculated and experimental values of Cp and w in the gaseous phase agree, with a deviation of 1%. 

Lagutina L. M. Thermodynamic Study of Difluorochloromethane Using Acoustic and Piezometric Methods. Author s Abstract of Candidate Thesis, MIFI, Moscow, 1967. 

The most widely used method for ionic liquid density measurement is the vibrating-tube densitometer a method which relies on a calibration as a function of temperature and pressure using appropriate reference fluid.For many reported ionic liquids this is not routinely performed and corrections for the case of viscous fluids (i.e., >100 mPas) are often ignored. Despite these factors the densities of ionic liquids measured with vibrating-tube densitometers have a standard uncertainty to within 0.1%. Alternative methods include the calculation of density through speed of sound measurements or piezometric methods. Both approaches are relatively complex technically but present the advantage of providing extra thermodynamic property data. 

---