Solid pycnometric density

Thus, there are two limitations of the pycnometric technique mentioned possible adsorption of guest molecules and a molecular sieving effect. It is noteworthy that some PSs, e.g., with a core-shell structure, can include some void volume that can be inaccessible to the guest molecules. In this case, the measured excluded volume will be the sum of the true volume of the solid phase and the volume of inaccessible pores. One should not absolutely equalize the true density and the density measured by a pycnometric technique (the pycnometric density) because of the three factors mentioned earlier. Conventionally, presenting the results of measurements one should define the conditions of a pycnometric experiment (at least the type of guest and temperature). For example, the definition p shows that the density was measured at 298 K using helium as a probe gas. Unfortunately, use of He as a pycnometric fluid is not a panacea since adsorption of He cannot be absolutely excluded by some PSs (e.g., carbons) even at 293 K (see van der Plas in Ref. [2]). Nevertheless, in most practically important cases the values of the true and pycnometric densities are very close [2,7],... 

In order to decide whether the nonstoichiometric phases contain interstitial anions, or vacant cation sites, we compared the pycnometric density with the calculated density for each type of defect. The experimental values agree with the last type of defects, and these solid solutions are represented using Rees s notation by... 

Selected properties of thorium oxide. Thorium oxide is a white, granular, slightly hygroscopic solid with a fluorite structure (lattice constant — 5.5859 0.0005) [18] and an x-ray density of 10.06. The Chemical Rubber Handbook of Chemistry and Physics [19] gives 10.03 as the density of thoria. Foex [20] gives pycnometric densities for thorium... 

After the purification by these methods, incombustible impurities and oxidized forms of carbon in the synthesized powders were assayed. For some samples, the pycnometric density was determined. The efficiency of the methods used to produce pure powders of ultradisperse diamonds was assessed based on these solid-phase parameters (Table 2.1). 

The volume of the solid phase Vp is usually measured by a pycnometric technique, which measures the excluded volume of a pycnometric fluid, whose molecules cannot penetrate the solid phase of PS. A simple example of a pycnometric fluid is helium [55], The pycnometric fluid fill in all void space (pores) accessible to it, and presumably do not adsorb on the surface of PS. In the case of microporous PSs, measurement of the volume accessible for guests with various sizes allows the determination of a distribution of micropores volume vs. the characteristic size of guest molecules. This approach lays the basis of the method of molecular probes. The essence of this method is in the following we have a series of probe molecules with different mean sizes (dl>d2>d3>---). The pycnometric measurements of the excluded volume will give a series The difference A V=Vpi-Vpi(i>j) corresponds to the volume of micropores with pycnometric sizes of d in a range dt[Pg.283]

The apparent density 5 (g/cm3) is usually measured using mercury as a pycnometric fluid. Mercury does not wet most of the solids and, thus, does not penetrate pores until pressure is applied. Mercury is not the only choice highly dispersed powders can serve as a guest fluid with the same penetration properties as well [55], Reciprocal to S is the specific apparent volume of PS, which is equal to the sum of the volumes of the pores and solid phase (e.g., the total volume of a granule shown in Figure 9.17a), and is obviously related to the mass of a PS. Relation between true and apparent density and porosity was considered in Problem 4. 

Except for LiC104, which is stable for some distance above its melting point, no molten salt densities seem to have been measured. Most ambient- temperature measurements are of fairly low accuracy. The most reasonable values have been listed for convenience. These are obtained either experimentally (usually pycnometrically, by displacement of a liquid such as CC14) or calculated from X-ray data. Solids frequently exhibit voids and/or occlude solvent so that reported values may scatter considerably. X-ray values are those for a perfect lattice and thus are only approximate guides to densities of real crystals. Whenever recent data are not available, the evaluation from International Critical Tables has been accepted. 

The weight of solids per unit-volume of suspension, W, entails no difficulty in its determination pycnometric methods, or simply by weighing a given "amount and displacement in a calibrated graduate. 

A study of mioroseotions showed that the alloys containing up to 20% A (CdTe, ZnTe) were single-phase. An increase in the amount of the A B compound was accompanied by an increase in the second phase. The microhardness of the alloys, determined with a PMT-3 instrument, confirmed the results of the microstructural analysis. The microhardness results are given in Table 1. The density of the solid solutions was measured pycnometrically. 

Preparation and properties of the hexahydrate correspond to LiLa(Se04)2 6H20, see p. 504. The pycnometrically determined density is 3.03 g/cm at 25°C. The angle of extinction is 4°. UV spectra of the solid double selenate and of corresponding solutions are compared, G6mez Madrazo et al. [4]. 

From chemical, gravimetric and X-ray structural analysis a complete solid solution Lai jSm B5 was found, usually deviating from stoichiometry towards boron defects. Comparison of pycnometric (measured in toluene) and X-ray densities revealed the existence of metal vacancies. Due to the change in the proportion of the Sm " " and Sm + ions the magnetic susceptibility depends nonlinearly on the La concentration (30% Sm + in SmB to 50% Sm + for 80% LaB ). 

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