Cloud point, definition

Petroleum becomes more or less a plastic solid when cooled to sufficiently low temperatures. This is due to the congealing of the various hydrocarbons that constitute the oil. The cloud point of petroleum (or a product) is the temperature at which paraffin wax or other solidifiable compounds present in the oil appear as a haze when the oil is chilled under definitely prescribed conditions (ASTM D2500, D3117). As cooling is continued, petroleum becomes more solid, and the pour point is the lowest temperature at which the oil pours or flows under definitely prescribed conditions when it is chilled without disturbance at a standard rate (ASTM D97). 

Cloud Point. An empirical cloud point analysis is performed by stirring a sample of fat while it is being cooled until the oil has clouded enough to block a light beam of known intensity. Both cloud point and congeal point values are more closely related to consistency than melting points. A definite relationship exists between the cloud point results and the solid fat index values at 92°F or 33.3°C. Cottonseed oil that has not been winterized or hydrogenated will have a cloud point of 30°F to 38°F or —1.1°C to 3.3°C. Winterized cottonseed salad oil, with the hard fraction removed, will have a cloud point of approximately 22°F to 26°F or —5.6°C to -3.3°C. 

When a uniform mother solution is cooled very slowly, a second phase begins to separate at a definite temperature Tp, which is called the cloud-point temperature or the cloud point. The cloud-point curve refers to Tp plotted against the composition of the mother solution. Since the second phase is infinitesimal in volume at the cloud point, we see from eq 1.11 that the cloud-point curve must satisfy the conditions ... 

The doud point of furfuryl alcohol is determined by dHuting 15 ml of the alcohol witn 30 ml of water and cooling the clear solution until ft becomes definitely doudy. The solution is then diowed to warm up with dirring until it is jud clear. At this poM. cooling produ an immediate cloudiness this temperature is recorded as the cloud point (9). 

Cloud point n. (1) In condensation polymerization, the temperature at which the first turbidity appears, caused by water separation when a reaction mbcture is cooled. (2) In petroleum and other oils, the falling temperature at which the oil becomes cloudy, from precipitation, of wax or other solid. (3) Point at which a definite lack of clarity (cloudiness) appears when a liquid is... 

Using the experimental data of cloud point measurements for PS/PI pairs given in Table 7.5, obtain an expression for a defined by Eq. (7.2) for each PS/PI pair. Use Eq. (7.4) for the temperature-dependent specific volume of PS, Vpg, and Eq. (7.5) for the temperature-dependent specific volume of PI, Vpj. Convert a (having the units of mol/cm ) to Elory-Huggins interaction parameter x using the definition of molar reference volume, Vref = being the molec-... 

Aqueous solutions of f. show unusual behavior depending on the number of ethylene oxide units for a given alkyl chain, they get turbid at elevated temperatures and have a definite cloud point, which can be used for analytical characterization. They have their optimum surface activity close to this cloud point. 

The intensity of shading at any point represents the magnitude of 1, i.e. the probability of finding the electron at that point. This may also be called a spherical charge-cloud . In helium, with two electrons, the picture is the same, but the two electrons must have opposite spins. These two electrons in helium are in a definite energy level and occupy an orbital in this case an atomic orbital. 

Depending on the application, models of molecular surfaces arc used to express molecular orbitals, clcaronic densities, van dor Waals radii, or other forms of display. An important definition of a molecular surface was laid down by Richards [182] with the solvent-accessible envelope. Normally the representation is a cloud of points, reticules (meshes or chicken-wire), or solid envelopes. The transparency of solid surfaces may also be indicated (Figure 2-116). 

Climate is often viewed as the aggregate of all of the elements of weather, with quantitative definitions being purely physical. However, because of couplings of carbon dioxide and many other atmospheric species to both physical climate and to the biosphere, the stability of the climate system depends in principle on the nature of feedbacks involving the biosphere. For example, the notion that sulfate particles originating from the oxidation of dimethylsulfide emitted by marine phytoplankton can affect the albedo (reflectivity) of clouds (Charlson et ai, 1987). At this point these feedbacks are mostly unidentified, and poorly quantified. 

Under atmospheric conditions flame travel in an unconfined gas cloud precedes as definite flame front at a determinable velocity. For example, where the ignition point is located in the middle of a volume of a gas, the flame front tends to generally proceed as an expanding sphere from the point of origin. Flame... 

Each of these columns of this symmetrical matrix may be seen as representing a molecule in the subspace formed by the density functions of the N molecules that constitute the set. Such a vector may also be seen as a molecular descriptor, where the infinite dimensionality of the electron density has been reduced to just N scalars that are real and positive definite. Furthermore, once chosen a certain operator in the MQSM, the descriptor is unbiased. A different way of looking at Z is to consider it as an iV-dimensional representation of the operator within a set of density functions. Every molecule then corresponds to a point in this /V-dimensional space. For the collection of all points, one can construct the so-called point clouds, which allow one to graphically represent the similarity between molecules and to investigate possible relations between molecules and their properties [23-28]. 

Atoms in crystals cannot be regarded as scattering points the diameter of the electron cloud of an atom is of the same order of size as the distance between the centres of adjacent atoms—in fact, to a first approximation, the atoms in many crystals may be regarded as spheres of definite radius in contact with each other the electron clouds... 

Wavefunctions of electrons in atoms are called atomic orbitals. The name was chosen to suggest something less definite than an orbit of an electron around a nucleus and to take into account the wave nature of the electron. The mathematical expressions for atomic orbitals—which are obtained as solutions of the Schrodinger equation—are more complicated than the sine functions for the particle in a box, but their essential features are quite simple. Moreover, we must never lose sight of their interpretation, that the square of a wavefunction tells us the probability density of an electron at each point. To visualize this probability density, we can think of a cloud centered on the nucleus. The density of the cloud at each point represents the probability of finding an electron there. Denser regions of the cloud therefore represent locations where the electron is more likely to be found. 

Furthermore it remains to be pointed out that many molecules of potential astrophysical interest have been sought in interstellar clouds but have not been found. Some of the notable negative results include cyclic molecules and NO, H2C20 and others. However, at the present time it seems premature to draw definite conclusions since the detection limits are barely below the expected line intensities. We may note that CH4 which is expected to exist in interstellar space (Section IV) has no allowed pure rotational spectrum. However, Dorney and Watson (1972) have shown that a centrifugally induced dipole moment exists which produces a complicated forbidden rotational spectrum in the radio frequency and microwave regions. The particular transitions are very weak and have not yet been observed in the laboratory. 

When transformation of a less stable into a more stable phase occurs, the change does not take place at one moment throughout the whole phase, but proceeds from definite points or growth centres (nuclei). Such nuclei may form spontaneously in a supercooled phase, as is seen, for example, in the cloud formation produced on the cooling of a vapour by adiabatic expansion. The influence of dust particles and of gaseous ions in increasing the number of condensation nuclei, is well known. 

This apparent contradiction leads to the conclusion that a metal lattice is, in the normal ranges of temperature, filled with electrons in much the same way as, in the case of the heavier atoms, the inner energy levels are filled with their electrons this is why the cloud electrons are not normally affected by the relatively small energy increments associated with heating. In other words, in the metal lattice there are definite electron energy levels, which are just as fundamental, and from some points of view just as important, as the energy levels in atoms. This important idea will now be discussed in rather more detail. 

Aerosol particles in the atmosphere usually carry with them some moisture. The amount of water associated with the aerosol depends on the relative humidity. Increasing the relative humidity condenses more water onto the particles, until finally, when the vapor pressure of water exceeds the saturation point, a certain number of particles grows into fog or cloud droplets. Meterologists call these particles condensation nuclei, or simply nuclei. Fogs and clouds are treated as separate systems and are not included in the normal definition of the atmospheric aerosol, even though they represent an assembly of particles suspended in air and thus constitute an atmospheric colloid. The smoothness of the transition from an assembly of aerosol particles to one of cloud elements makes it difficult to define a boundary line between both colloids. Due to the overlap of size ranges of the particles in both systems, any division will be rather arbitrary. 

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