Measurement determining density

The extent of dissociation at a given temperature can be determined by measuring the density of the vapour. Since anhydrous sulphuric acid is less volatile than hydrogen chloride, ammonium sulphate does not readily sublime on heating some ammonia is evolved to leave the hydrogensulphate ... 

Density. Measurement of density is widely used in the sugar industry to determine the sugar concentration of symps, Hquors, juices, and molasses. The instmment used is called a hydrometer or a spindle. When it is graduated in sucrose concentration (percent sucrose by weight), it is called a Brix hydrometer or a Brix spindle. Brix is defined as the percent of dry substance by hydrometry, using an instmment or table caUbrated in terms of percent sucrose by weight in water solution. Hydrometers are also graduated in °BaumH, stiU in use in some industries. The relationship between °BaumH and density, ing/cm, is °Baumn Baum e = 145(1 — 1/d). 

Percentage compaction usually is used to measure soil density in a fill situation. Generally, the maximum Proctor specific weight (dry, Ib/ft ), determined by a standard laboratory test, is set up as the standard for the soil. Normally, 90-100% compaction is specified. 

Other methods for estimating the volume percentage of the interphases in a composition have been proposed, too, for example, measurements of density variations [76, 77], volume of compressed sample [78], the dielectric constant [77], etc. The important thing is that the interphase thickness determined in one way or another is an effective value dependent upon the conditions and type of the experiment by which it was determined [51]. 

Findings with PDU. Work with the PDU largely paralleled the bench-scale reactor tests there was one important addition—extensive three-phase fluidization studies. As was mentioned, the PDU is equipped with a traversing gamma-ray density detector that is capable of measuring bed density to within dbO.Ol specific gravity units. Thus, we could measure and correlate fluidized bed expansion as a function of liquid and gas velocities and physical properties, and could also determine the... 

The best way to determine the type of unit cell adopted by a metal is x-ray diffraction, which gives a characteristic diffraction pattern for each type of unit cell (see Major Technique 3 following his chapter). However, a simpler procedure that can be used to distinguish between close-packed and other structures is to measure the density of the metal we then calculate the densities of the candidate unit cells and decide which structure accounts for the observed density. Density is an intensive property, which means that it does not depend on the size of the sample (Section A). Therefore, it is the same for a unit cell and a bulk sample. Hexagonal and cubic close packing cannot be distinguished in this way, because they have the same coordination numbers and therefore the same densities (for a given element). 

All crystal structures are derived from the 14 Bravais lattices. The atoms in a unit cell are counted by determining what fraction of each atom resides within the cell. The type of unit cell adopted by a metal can be determined by measuring its density. 

Depth of EB penetration The depth of penetration of energetic electrons into a material at normal angle of incidence is directly proportional to the energy of the electrons and inversely proportional to the density of the material [49,50]. The depth is expressed as a product of penetration distance and the density of the material (i.e., 1 g/cm = 1 cm X 1 g/cm ). The radiation energy and thus the type of electron accelerator to be used are dependent on the required penetration depth, the density of the irradiated material, and the chosen irradiation system. If one measures the density (d) in gram per cubic centimeter (g/cm ) and the layer thickness (T) in millimeter (mm), one can determine the radiation energy ( ) necessary for optimal homogeneity from [40] ... 

Furche, F., Ahlrichs, R., Weis, P., Jacob, C., Gilb, S., Bierweiler, T. and Kappes, M.M. (2002) The structures of small gold cluster anions as determined by a combination of ion mobility measurements and density functional calculations. Journal of Chemical Physics, 117, 6982-6990. 

The purpose of this compilation is to tabulate the densities of compounds, hence only minimal description of experimental methods used to measure the density of liquids or solids appears. Detailed descriptions of methods for density determination of solids, liquids and gases, along with appropriate density reference standards, appear in a chapter by Davis and Koch in Physical Methods of Chemistry, Volume VI, Determination of Thermodynamic Properties [86-ros/bae],... 

The principal experimental method used to measure the density of a solid is determination of the mass of liquid displaced by a known mass of solid. It is essential that the solid have no appreciable solubility in the liquid, that all occluded air be removed from the solid and that the density of the displacement fluid be less than that of the solid lest the solid float. Densities of crystalline solids also can be determined from the dimensions of the unit cell. Davis and Koch discuss other methods for measuring the density of liquids and solids such as hydrostatic weighing of a buoy and flotation methods. 

It has also been inferred that differences found between crystallinities measured by density and those from heat of fusion by DSC area determination, as given for polyethylenes in the example of Figure 4 [72], may be related to baseline uncertainties, or not accounting for the temperature correction of AHc. Given that similar differences in crystallinity from density and heat of fusion were reported for isotactic poly(propylene) [43] and polyfaryl ether ether ketone ketone), PEEKK [73], other features of phase structure that deviate from the two-phase model may be involved in the crystallinity discrepancy. 

If transport were infinitely fast, the concentrations c x and c ed of nonadsorbing reacting species would be the same at the interface as in the bulk. The measured current density would solely be determined by the reaction, and would equal the kinetic current density. 

The volume of the unit cell and thus the volume occupied in the crystal by a single repeat unit, can be obtained from the repeat distance and the positions of the diffraction spots on the layer lines. This volume can measure the density of the crystals, that is useful in determining the degree of crystallinity. 

The instrument constant B can be determined by measuring the t in two fluids of known density. Air and water are used by most workers (22). In our laboratory we used seawater of known conductivity and pure water to calibrate our vibrating flow systems (53). The system gives accurate densities in dilute solutions, however, care must be taken when using the system in concentrated solutions or in solutions with large viscosities. The development of commercial flow densimeters has caused a rapid increase in the output of density measurements of solutions. Desnoyers, Jolicoeur and coworkers (54-69) have used this system to measure the densities of numerous electrolyte solutions. We have used the system to study the densities of electrolyte mixtures and natural waters (53,70-81). We routinely take our system to sea on oceanographic cruises (79) and find the system to perform very well on a rocking ship. 

Attempts have been made, using helium, to measure the density of the adsorbed phase 108-110) to try to find out whether the films are to be thought of as gaslike or liquidlike. The volume of the adsorbent was determined before adsorption, and then after a known amount of gas had been adsorbed. It was concluded 109) that the adsorption of helium, although small, was finite, introducing uncertainty in the results. Furthermore, while the concept of density is useful when multilayers are considered, it is not necessarily so at coverages less than unity. 

DENSITY MEASUREMENTS. Helium densities of the extracts were determined so that the gravimetric sorption data could be converted to volume fractions needed to calculate x parameters. The results of these measurements are shown in Table III. The density of the extract was observed to decrease with increasing size of the added alkyl group. These results are qualitatively similar to those of Liotta t al.(14), who studied the effects of O-alkylation on the physical structure of the native Illinois No. 6 coal. 

For direct comparison of explosives, it is frequently convenient to select pj-=1.0g/cc. While the actual vel of a given chge may be measured with present methods with an accuracy of ca 0.1%, the D(pj) curve is seldom known this accurately, owing to fluctuations in density of the chge and exptl error in the evaluation of p. In cast, pressed and liquid expls, it is possible to determine density very accurately, but in loose, granular chges an accuracy better than 2.0% is seldom attained. For this reason the literature frequently shows discrepancies of this magnitude in D pj° and M factor of eq 3.1. Table 3.1... 

The values agree well in position with those of Woldbye (17) (which were for solutions M in sodium nitrate), but our extinction coefficients are consistently about 10% higher than his. In addition, we note a weak maximum for T at 330 m/i and report some information on the spectra in the doublet region. These last measurements were made on filtered 0.04M solutions, using 5 cm. cells. The general absorption curves were obtained by a Cary Model 14 spectrophotometer, but for most of the kinetic studies and analytical measurements, optical densities at selected wave lengths were determined by a DU Beckman spectrophotometer. 

Emulsion Stability. The stability of the emulsions was determined by measuring optical density of the solutions following centrifugation. A 0.2% solution of each spray dried powder was prepared in water and the optical density read at 400 nm in a Coleman spectrophotometer. A 0.16% solution of carrier (gum arabic) was used as a blank. This is based on a carrier to flavor ratio of 4 1. The initial optical density of each solution was read and then the solutions were centrifuged in an lEC International Centrifuge at 500 x g for 5, 10, 15, 30, 45 and 60 min. The optical density was read after each time period. 

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