Pycnometry liquid

The methods depicted in Sections Pycnometry , Liquid Intrusion and Capillary Condensation of Gases (Gas Adsorption) require so called bulk samples, where the amount of probe molecule is in the mmol to /rmol range. When the thickness of films or fibers becomes very small, reliable measnrements cannot be carried out, due to the limit of absolute detection. In addition, these methods give only averaged information over the whole loaded samples, and no local deviation or heterogeneity, such as that across the film thickness, can be detected. For such purposes, methods utilizing 3-D imaging have become recently available (Jinnai et al., 2000 Koster et al., 2000). 

The three most common ways of obtaining true density measurements are gas pycnometry (gas displacement), liquid displacement, and flotation in a liquid. These three techniques have been compared based on accuracy, ease of use, and instrumentation [63], and the results are summarized in Table 4. Gas pycnometry will be discussed in this section because of its wide use and ease of operation. 

Flotation in liquid Simple operation Inexpensive Demonstrates density distribution Accurate to 4 significant figures More time consuming than gas pycnometry Density vs. temperature curve suggested for each liquid Sample should be insoluble in liquid... 

In pycnometry, the sample is weighted in a calibrated pycnometer before and after this is filled with a liquid of known density. The volume of the sample and thus its mass is determined. Powders may be used, and it is often advantageous to... 

In this model, the buoyant mass is then the sum of the buoyant mass of the three components, assuming that these are independent of the mass of solvent occupied in the solvation shell. Thus, the mass of the adsorbed shell can be calculated if information about the mass and density of the core particle and the density of the macromolecule and solvent are known. Photon correlation spectroscopy, electron microscopy, flow FFF, or other sizing techniques can readily provide some independent information on the physical or hydrodynamic particle size, and pycnometry can be used to measure the densities of the colloidal suspension, polymer solution, and pure liquid. 

The bulk density of materials was measured by Hg pycnometry from independent measurements of the mass and the volume of monolithic samples. The geometrical volume of the sample is determined fi om the weight difiference between a flask (calibrated volume) filled up with mercmy and the same flask filled up with the sample and mercury. As mercury is a non-wetting liquid and as no pressure is exerted, mercury does not enter in the porosity of the sample or crush it. 

Bulk density is easily measured from the volume occupied by the bulk solid and is a strong function of sample preparation. True density is measured by standard techniques using liquid or gas pycnometry. Apparent (agglomerate) density is difficult to measure directly. Hink-ley et al. [Int. J. Min. Proc., 41, 53-69 (1994)] describe a method for measuring the apparent density of wet granules by kerosene displacement. Agglomerate density may also be inferred from direct measurement of true density and porosity by using Eq. (21-96). 

Using simple, classical pycnometry, Etzler and Fagundus (1983) have measured the density of water and some other liquids inside the pores of a silica gel with an average pore diameter of 140 A. With acetone and methanol, the observed densities were close to the values reported for bulk liquids however, for water a value of 0.966 g/cm was obtained (compared to a bulk value of 0.997 g/cm at 25°C), i.e. 3% lower than the bulk value. 

For liquids at ambient conditions, one can obtain a reasonably accurate density simply by weighing a known volume of the liquid. For rough work, one can use something as simple as a volumetric flask for more precise work, calibrated volumes (known as pycnometers) are used. One can easily obtain 1% accuracy, and careful pycnometry can obtain 0.1%. 

The true density is thus a property of the material and is independent of the method of determination. In this respect, the determination of the true density can be determined using three methods displacement of a liquid, displacement of a gas (pycnometry) or floatation in a liquid. These methods of measuring true density have been evaluated by Duncan-Hewitt and Grant (1986). They concluded that, whereas liquid displacement was tedious and tended to underestimate the true density, displacement of a gas was accurate but needed relatively expensive instrumentation. As an alternative, the floatation method was found to be simple to use and inexpensive. Although more time consuming than gas pycnometry, it was accurate using relatively simple instrumentation. 

Density is another physical constant which is not very sensitive to impurities. Although the densities of liquids can be determined with very high accuracy by pycnometry, the measurement of density is not suitable for the detection of impurities occurring in micro amounts. 

Any of the three particle densities defined above should not be confused with bulk density of materials, which includes the voids between the particles in the volume measured. The different values of particle density can be also expressed in a dimensionless form, as relative density, or specific gravity, which is simply the ratio of the density of the particle to the density of water. It is easy to determine the mass of particles accurately but difficult to evaluate their volume because they have irregular shapes and voids between them. The apparent particle density, or if the particles have no closed pores also the true density, can be measured by fluid displacement methods, that is, pycnometry, which are in common use in industry. The displacement can be carried out using either a liquid or a gas, with the gas employed normally being air. Thus, the two known techniques to determine true or apparent density, when applicable, are liquid pycnometry and air pycnometry. 

Descriptive diagram of density determination by liquid pycnometry (a) description of pycnometer, (b) weighing, (c) filling to about 1/2 with powder, (d) adding liquid to almost full, (e) eliminating bubbles, and (f) topping and final weighing. 

The apparent density, also called the true density, real density, or absolute density, expressed in kg.m is obtained when the volume measured excludes the pores as well as the void spaces between particles within the bulk sample. Absolute density is determined by pycnometry using water or another Hquid that is expected to fill the pores in the sample, thus removing their volume from the measurement. Sometimes the material is subjected to boiling in the same liquid to ensure pore penetration, and sometimes the sample is evacuated prior to immersion to assist pore filling. However, surface-tension effects and entrapped gases resist the filling of very small pores. Therefore the best method consists in determining the apparent density by hehum pycnometry ... 

The following data were obtained in a liquid pycnometry experiment performed at 20°C mass of pycnometer = 35.827 g mass of pycnometer and powder = 46.402 g mass of pycnometer and water = 81.364 g mass of pycnometer, powder, and water = 89.894 g. If the theoretical density of the solid is 5.605 g/cm, determine... 

Bulk and apparent density Helium pycnometry Mercury porosimetry Liquid displacement Surface energy Thermal analysis tests Tempera ture-progra m med desorption and reaction Calorimetry... 

Although more labor-intensive and less efficient, information on the densification kinetics and densification can also be obtained from density measurements on different individual samples as a function of time for otherwise identical sintering conditions. Bulk density measurements on <92% dense sintered samples containing open porosity can be determined from the measured mass and dimensions of the compact, while Archimedes method works well for closed pore, >92% dense bodies. The density of closed pore samples can also be determined by pycnome-try (e.g., helium pycnometry),, 37 mercury porosimetry, and by the sink-float method (i.e., whereby the buoyancy of the sample is assessed and compared in different density liquids). Density can also be estimated from micrographs using quantitative stereology. 

Two standard methods (mercury porosimetry and helium pycnometry) together with liquid expulsion permporometry (that takes into account only flow-through pores) were used for determination of textural properties. Pore structure characteristics relevant to transport processes were evaluated fiom multicomponent gas counter-current difhision and gas permeation. For data analysis the Mean Transport-Pore Model (MTPM) based on Maxwell-Stefan diffusion equation and a simplified form of the Weber permeation equation was used. 

The temperature dependence of the specific volume of the sample was measured by pycnometry. The results show no discontinuity at OOT. If the OOT is a first-order phase transition like the liquid-gas phase transition, one may expect discontinuity in volume at OOT. However, even if the OOT is a first-order phase transition, it may not necessarily involve a discontinuity in volume because the transition involves only a symmetry change in the liquid-liquid microphase-separated phases. 

Pycnometry is a method designed to determine the precise mass-volume relationships of liquids or solids. The measurement is performed using a device called a pycnometer, a glass bulb fitted with a stopper through which runs a capillary bore. By filling the inside... 

In practice pycnometry can be used to measure the density of liquid polymers by placing them in a cup of known volume and mass. A cover containing a capillary through which the overflow can pass for removal is typically added. Since both the volume of the cup as well as the density of the liquid adhesive are temperature dependent, accurate readings require that temperature be carefully controlled for the test. The standard cup can be filled with a liquid adhesive that is below the desired test. Then the cup and adhesive are heated to the temperature at which the density is to be determined, and the mass is determined after the excess is wiped from the overflow orifice (ASTM-D1875-03 2003). 

Particle density is often determined by some sort of pycnometry. If a liquid is used as the pycnometric fluid, this is mostly done in a so-called density bottle , where the masses are determined of ... 

The film may be removed from the substrate and the density determined by displacement techniques.Pycnometry involves the displacement of a liquid or gas from a container of accurately known volume and the weight of the sample. Density gradient columns utilize a thermal gradient to produce a density gradient in a liquid. The sample will float at a level of the same density fluid. Calibration floats are used to determine the density. Fluids having densities of up to 3.3254 g/cm (methylene iodine solution) are available. The most accurate techniques have been developed to study radiation-induced void formation in metals, and they utilize hydrostatic weighing (in and out of a fluid) of small samples (30 mg) with a microbalance to a precision of 0.04%. 

Pycnometry measurement of the change in weight of a sample of cement paste plus extra water (or oil) additional liquid is added to a constant volume before measurement... 

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