Volume of fusion

One of the models that can be used to approximately predict the properties of molten salts is called the hole model. The outstanding fact that led to this model is the large volume of fusion (10-20%) exhibited by simple salts on melting (Fig. 5.17). The basic idea of this rather artificial model is that within the liquid salt are tiny volume... 

There is a linear relation between the free volume from sound velocity measurements and the hole volume (from volume of fusion data). 

In Equation (19), the enthalpy and entropy changes refer to values at 1 bar and the volume of fusion is pressure dependent. The main difficulty with the practical application of (19) to partitioning relations is, as discussed earlier, finding appropriate ways of connecting the weight partition coefficient D to its thermodynamic expression K. This requires making assumptions about the relationship between composition and activity of the component REEMgAlSiOg. 

On the left-hand side of Equation (23) the 1 bar enthalpy and entropy of fusion are both temperature dependent, but because of the opposite signs in the equation their temperature dependence tend to cancel one another (Wood and Fraser, 1976, p. 29). This means that AG° can generally be calculated reasonably accurately over a wide temperature range with fixed values of enthalpy (A//f) and entropy (A5 ). However, the volume of fusion ATf is, because of the compressibility of the liquid, rather pressure dependent. Assuming that the pressure dependence is linear. Equation (23) yields... 

Calorimetric and dilatometric studies of fusion are important in the study of the mechanism of melting where the entropy and volume of fusion are important parameters. ... 

Bourova E, Richet P (1998), CJuartz and cristobalite high-temperature cell parameters and volumes of fusion. Geophys Res Let 25 2333-2336... 

Nitrogen and sulphur present. Just acidify 2-3 ml. of the fusion solution with dilute nitric acid, and evaporate to half the original volume in order to expel hydrogen cyanide and/or hydrogen sulphide which may be present. Dilute with an equal volume of water. If only one halogen is present, proceed as in tests (i) or (iii). If one or more halogens may be present, use tests (ii), (iii) or (iv). 

Phosphorus. The presence of phosphorus may be indicated by a smell of phosphine during the sodium fusion. Treat 1 ml. of the fusion solution with 3 ml. of eoneentrated nitric acid and boil for one minute. Cool and add an equal volume of ammonium molybdate reagent. Warm the mixture to 40-50°, and allow to stand. If phosphorus is present, a yellow erystalline precipitate of ammonium phosphomolybdate wUl separate. 

If the amorphous component contributes nothing to the measured property (as with heat of fusion), then Eq. (4.39) reduces to Eq. (4.37). Specific volume is an example of a property which has been extensively used in this way to evaluate 6. 

High temperature is an important requirement for the attainment of fusion reactions in a plasma. The conditions necessary for extracting as much energy from the plasma as went into it is the Lawson criterion, which states that the product of the ion density and the confinement or reaction time must exceed 10 s/cm in the most favorable cases (173). If the coUisions are sufficiently violent, the Lawson criterion specifies how many of them must occur to break even. Conventional magnetic confinement involves fields of as much as 10 T (10 G) with large (1 m ) plasmas of low densities (<10 particles/cm ) and volumes and reaction times of about 1 s. If the magnetic flux can be compressed to values above 100 T (10 G), then a few cm ... 

Many solid substances (camphor, iodine, naphthalene, etc.), are known which are appreciably volatile at ordinary temperatures. Others, such as the metals, are apparently quite fixed, but they probably possess a definite, although very small vapour-pressure, even at ordinary temperatures. Thus, if magnesium is heated to 550° for a few hours in a magnesia boat enclosed in a vacuous tube it sublimes in beautiful crystals on the cool part of the tube. The vaporisation of a solid without previous fusion is called sublimation the vapour-pressure (like the vapour-pressure of a liquid), is definite for each temperature, is independent of i the volume of the vapour space, and increases with rise of temperature. 

Lindemann <8> has made an interesting application of the new theory in the determination of the frequency of atomic vibration, r, from the melting-point. He assumes that at the melting-point, T the atoms perform vibrations of such amplitude that they mutually collide, and then transfer kinetic energy like the molecules of a gas. The mean kinetic energy of the atom will then increase by RT when the liquid is unpolymerised and the fusion occurs at constant volume this is the molecular heat of fusion. 

In section 3.6.3 we mentioned that in growth on a curved face the strain surface free energy os takes the role the lateral surface free energy tr played in the flat surface case, namely that of a barrier to the formation of the first stem. This analogy cannot be made since, in contrast to surface free energy is associated with the deposition of any stem. Therefore and because of its physical origin (the volume strain) it is closely linked with the free energy of fusion. This is... 

The pressure exerted by the radiation escaping from inner portions of the star counteracts the force of gravity, and the balance of the two opposing forces keeps the volume of the star constant as long as hydrogen fusion continues. 

The heat of fusion AHf (obtained from the area under the DSC melting curve) and percentage crystallinity calculated from AHf is found to be linearly dependent on butadiene content, and independent of the polymer architecture. This is shown in Figure 3. Also, the density of the block copolymers was found to be linearly dependent on butadiene content (see Figure 4). The linear additivity of density (specific volume) has been observed by other workers for incompatible block copolymers of styrene and butadiene indicating that very little change in density from that of pure components has occurred on forming the block copolymers.(32) While the above statement is somewhat plausible, these workers have utilized the small positive deviation from the linear additivity law to estimate the thickness of the boundary in SB block copolymers.(32)... 

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