Lowest temperature

Fuel-air mixtures at or around stoichiometric concentration have the lowest autoignition temperature, lowest minimum ignition energies, and highest burning velocities. 

Technology/ICI temperatures—lowest total manufacturing cost 33 2001... 

In order to cool the melt from high 0 = 0) to low temperatures (lowest temperature = 20), P is increased according to the cooling schedule (16-18)... 

Ignition temperature—Lowest temperature at which a substance can catch fire and continue to burn. 

Brittle point, brittle temperature Lowest temperature at which a material withstands an impact test under standardized conditions. 

FIG U RE 11.3 In situ IR spectra of methanol adsorbed over 5% V205/Ti02 during methanol oxidation as a function of temperature (lowest temperature on top 100,200, 225, 250, 275, and 300°C) (From Burcham, LJ. and Wachs, I.E. Catal. Today 1999, 49, 467-484. With permission.)... 

Lowest operating temperature Lowest ambient temperature. Vehicle/plant overnight storage. Chill factor on exposed equipment. Fuel quality/waxing temperature. 

Below the temperature of the lowest experimental datum, standard-state fugacities were obtained by simple extrapolation. Uncertainties assigned to these fugacities are largest when the fugacities are smallest, for two reasons (1) the extrapolation... 

At temperatures above those corresponding to the highest experimental pressures, data were generated using the Lyckman correlation all of these were assigned an uncertainty of 5% of the standard-state fugacity at zero pressure. Frequently, this uncertainty amounts to one half or more atmosphere for the lowest point, and to 1 to 5 atmospheres for the highest point. 

Flash point. The flash point of a liquid is the lowest temperature at which it gives off enough vapor to form an ignitable mixture with air. The flash point generally increases with increasing pressure. 

Nevertheless, this type of analysis, usually done by chromatography, is not always justified when taking into account the operator s time. Other quicker analyses are used such as FIA (Fluorescent Indicator Analysis) (see paragraph 3.3.5), which give approximate but usually acceptable proportions of saturated, olefinic, and aromatic hydrocarbons. Another way to characterize the aromatic content is to use the solvent s aniline point the lowest temperature at which equal volumes of the solvent and pure aniline are miscible. 

The pour point is the lowest temperature at which an oil can still pour while it is cooled, without agitation, under standardized conditions. The pour point of paraffinic bases is linked to the crystallization of n-paraffins. The pour point of naphthenic bases is related to a significant viscosity increase at low temperatures. This property can be improved by additives. 

For a free energy of fonnation, the preferred standard state of the element should be the thennodynamically stable (lowest chemical potential) fonn of it e.g. at room temperature, graphite for carbon, the orthorhombic crystal for sulfiir. 

Many substances exist in two or more solid allotropic fomis. At 0 K, the themiodynamically stable fomi is of course the one of lowest energy, but in many cases it is possible to make themiodynamic measurements on another (metastable) fomi down to very low temperatures. Using the measured entropy of transition at equilibrium, the measured heat capacities of both fomis and equation (A2.1.73) to extrapolate to 0 K, one can obtain the entropy of transition at 0 K. Within experimental... 

In an ideal Bose gas, at a certain transition temperature a remarkable effect occurs a macroscopic fraction of the total number of particles condenses into the lowest-energy single-particle state. This effect, which occurs when the Bose particles have non-zero mass, is called Bose-Einstein condensation, and the key to its understanding is the chemical potential. For an ideal gas of photons or phonons, which have zero mass, this effect does not occur. This is because their total number is arbitrary and the chemical potential is effectively zero for tire photon or phonon gas. 

Figure C2.17.10. Optical absorjDtion spectra of nanocrystalline CdSe. The spectra of several different samples in the visible and near-UV are measured at low temperature, to minimize the effects of line broadening from lattice vibrations. In these samples, grown as described in [84], the lowest exciton state shifts dramatically to higher energy with decreasing particle size. Higher-lying exciton states are also visible in several of these spectra. For reference, the band gap of bulk CdSe is 1.85 eV.

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