Temperature, absolute reduced

Dew-point Temperature (DPT). DPT is the temperature at which the condensation of water vapor in a space begins for a given state of humidity and pressure as the temperature is reduced. It is the temperature corresponding to saturation (100% rh) for a given absolute humidity at constant pressure. 

To a solution of 112 (2.0 g, 43.0 mmol) in 50 mL of dry THF at -65°C was added a solution of 111 (4.45 g, 34.0 mmol) in 100 mL of absolute ethanol containing 5 mL of acetic acid cooled to - 65°C in one portion. After stirring for 15 min., dry triethylamine (4.8 g, 510 mmol) was added. The reaction continued for 24 h with slow warming to room temperature before reducing the volume to 10 mL. The crude 113 was brought to pH 10 with potassium carbonate. The aqueous solution was continuously extracted with chloroform, dried (K2CO3), evaporated onto neutral alumina, placed on a column of neutral alumina (50 g) and eluted with chloroform. The solvent was evaporated and the residue crystallized from ethanol to yield 113 (2.86 g 55%). The yellow solid had a mp = 72.5-73.8°C. 

Figure 12-15 is a compressibility chart for natural gas based on pseudo-reduced pressure and temperature. The reduced pressure is the ratio of the absolute operating pressure to the critical pressure, P and the reduced temperature is the ratio of the absolute operating temperature to the critical temperature, T, for a pure gas or vapor. The pseudo value is the reduced value for a mixture calculated as the sum of the mol percentages of the reduced values of the pure constituents. 

A 2-1. three-necked flask is mounted on a steam bath and fitted with a reflux condenser, a separatory funnel, and an efficient sealed stirrer. In the flask is placed 600 cc. of absolute alcohol, and to this is added gradually 46 g. (2 gram atoms) of clean sodium cut into small pieces.1 The sodium ethoxide solution is stirred and cooled to room temperature, after which 267 g. (260 cc., 2.05 moles) of ethyl acetoacetate (Note 1) is added slowly through the separatory funnel. The reflux condenser is then replaced by a short still head, and the alcohol is removed by distillation at approximately room temperature and under the pressure of a water pump. When approximately half the alcohol has been removed, sufficient sodium enolate precipitates so that stirring has to be discontinued. When the residue appears dry (after about two hours) the last traces of alcohol are removed by heating for an hour on the steam bath under a pressure of 2 mm. The flask is allowed to cool to room temperature under reduced pressure. 

Niobium alloyed with germanium becomes a superconductor of electricity that does not lose its superconductivity at 23.2° Kelvin as large amounts of electrical current are passed through it, as do some other superconductive alloys. In the pure metallic state, niobium wires are also superconductors when the temperatures are reduced to near absolute zero (—273°C). Niobium alloys are also used to make superconductive magnets as well as jewelry. 

The results of the distillation tests indicated that boiler operation at pressures near 200 mm Hg absolute reduces boiling temperatures. These lower temperatures should also reduce N0X evolution and decrease the rate of degradation of the materials of construction. 

Frequently, the context of a particular problem requires us to consider the limiting behaviour of a function as the value of the independent variable approaches zero. For example, consider the physical measurement of heat capacity at absolute zero. Since it is impossible to achieve absolute zero in the laboratory, a natural way to approach the problem would be to obtain measurements of the property at increasingly lower temperatures. If, as the temperature is reduced, the corresponding measurements approach some value m, then it may be assumed that the measurement of the property (in this case, heat capacity) at absolute zero is also m, so long as the specific heat function is continuous in the region of study. We say in this case that the limiting value of the heat capacity,... 

As mentioned earlier, proteins are subject to cold denaturation because they exhibit maximal stability at temperatures greater than 0°C. The basis of this effect is the reduction in the stabilizing influence of hydrophobic interactions as temperature is reduced. Recall that the burial of hydrophobic side-chains in the folded protein is favored by entropy considerations (AS is positive), but that the enthalpy change associated with these burials is unfavorable (AH, too, is positive). Thus, as temperature decreases, there is less energy available to remove water from around hydrophobic groups in contact with the solvent. Furthermore, as temperature is reduced, the term [— TAS] takes on a smaller absolute value. For these reasons, the contribution of the hydrophobic effect to the net free energy of stabilization of a protein is reduced at low temperatures, and cold-induced unfolding of proteins (cold denaturation) may occur. 

In Equation (1.3), the volume of the gas becomes zero when the temperature is reduced to -273.15°C, which is the absolute zero temperature. The relation between the Celsius degree and the absolute scale (called Kelvin degree) is given by ... 

In order to achieve the longest shelf life possible, all equipment and packaging which has contact with the product must be absolutely clean in order to reduce bacterial growth to a minimum. The shelf-life of the juice can be increased by pasteurisation at low temperatures which reduces the microbiological count, but does not necessarily produce a sterile product. The flavour of the juice should not be influenced in any way by this treatment. 

Steam distillation is the main commercial extraction procedure for the production of essential oils from almost any type of plant material. Solvent extraction is also used commercially and yields a resinoid, concrete or absolute according to the solvents and techniques used (see Chapter 4). Both steam distillation and solvent extraction are used on a laboratory scale to produce oils and extracts for analysis. Other methods of extraction, such as supercritical fluid extraction (SFE), which uses supercritical CO2 as the extraction solvent, are now being developed and used on both commercial and laboratory scales. The extracts produced by SFE may contain different materials from the steam-distilled oil because of the solvating power of C02 and the lower extraction temperature, which reduces thermal degradation. The C02 extract may therefore have an odour closer to that of the original material and may contain different fragrant compounds. The choice of extraction procedure depends on the nature and amount of material available, and the qualities desired in the extract. Solvent extraction is better suited to small sample amounts or volatile materi-... 

As the temperature is reduced, the lower energy states become more probable until at absolute zero the system occupies the lowest possible energy state. 

The fact that the absolute zero of temperature cannot be attained and that it becomes more and more difficult to approach that temperature suggests that the entropies of all materials at absolute zero are the same. However, this statement must be qualified slightly by adding that the substance must be in its thermodynamically most stable state. For example, many substances are frozen into a metastable glassy state as the temperature is reduced. This state will persist indefinitely because of the slowness with which processes occur at low temperatures. Therefore we must exclude noncrystalline... 

This is the temperature at which a vapor-gas mixture becomes saturated when cooled at a constant total pressure out of contact with a liquid (i.e., at constant absolute humidity). The concept of the dew point is best illustrated by referring to Figure 1.3, a plot of the absolute humidity versus temperature for a fixed pressure and the same gas. If an unsaturated mixture initially at point F is cooled at constant pressure out of contact of Uqnid, the gas saturation increases until the point G is reached, when the gas is fully saturated. The tanperature at which the gas is fully saturated is called the dew point 7],. If the temperature is reduced to an infinitesimal amount below Tj, the vapor will condense and the process follows the saturation curve. 

The term supercritical injection can refer to several different types of processes. There are four classes (note that is reduced absolute temperature andis reduced absolute pressure the subscript inj refers to injection, and env represents the environment) ... 

Hansen firstly determined d for a solvent using the homomorph concept. The energy of vaporisation of a hydrocarbon molecule of the same size and shape as the solvent molecule in question at the same reduced temperature (absolute temperature divided by the critical temperature) is assumed to be that due to dispersion forces existing in the solvent. The difference between the energy of vaporisation of the solvent, AE, and that calculated as the contribution due to dispersion forces, A d, is taken as that due to both polar and hydrogen bonding forces, i.e. ... 

T - absolute temperature, K T - characteristic temperature f - reduced temperature (=T/T )... 

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