Temperature, conversion factors measurement

EC 3.2.1.1.). The measuring temperature for reference methods is 30°C. When a result is obtained at a temperature other than 30°C, it should be related to that of the reference method. This can be done by using the reference materials or a temperature conversion factor. 

Integers and exact numbers In multiplication or division by an integer or an exact number, the uncertainty of the result is determined by the measured value. Some unit conversion factors are defined exactly, even though they are not whole numbers. For example, 1 in. is defined as exactly 2.54 cm and the 273.15 in the conversion between Celsius and Kelvin temperatures is exact so 100.000°C converts into 373.150 K. 

Accurate determination of the density or specific gravity of crude oil is necessary for the conversion of measured volumes to volumes at the standard temperature of 15.56°C (60°F) (ASTM D1250 IP 200 Petroleum Measurement Tables). The specific gravity is also a factor reflecting the quality of crude oils. 

For chemical reactions and phase transformations, the energy absorbed or liberated is measured as heat. The principal unit for reporting heat is the calorie, which is defined as the energy needed to raise the temperature of 1 gram of water at l4.5° C by a single degree. The term kilocalorie refers to 1,000 calories. Another unit of energy is the joule (rhymes with school), which is equal to 0.239 calories. Conversely, a calorie is 4.184 joules. The translation of calories to joules, or kilocalories to kilojoules, is so common in chemical calculations that you should memorize the conversion factors. 

In equation (18.1), E1 is the standard potential and is a constant that includes all other potentials, R is the ideal gas constant, T is the temperature, z is the charge carried by ion i to be measured and whose activity is a, F represents Faraday s constant and 2.303 is the logarithmic conversion factor. 

Conversion factors for various pressure units and flow units are given in Table VI.1. Table VI.2 lists values of the ratio d,/do (the density of mercury at a temperature t divided by the density of mercury at 0°C) over the temperature range 0-99°C. Capillary depression corrections for mercury in glass tubes are given in Table VI.3. The complete set of corrections for a pressure measurement is made as follows ... 

It should be noted that TDS meters actually measure electrical conductivity (in pS/cm) and employ a built-in conversion factor. Conductivity in water is by means of ionic motion and increases with temperature, and therefore a reference temperature is normally used (25°C). 

The strength of the bioassay approach is that it directly estimates the fraction of natural DOC that can be used by a natural microbial assemblage under defined conditions. However, there are numerous manipulations of water samples during bioassay incubations, and the effects of these manipulations on the measured parameters are not well known. For example, containment of water samples can rapidly alter microbial population structure. Nutrients, rather than carbon, can be limiting for microbial utilization of DOM. Moreover, there are no standard protocols for bioassay experiments. Different indicators of DOM utilization are measured by different investigators, and many of the measured parameters rely on conversion factors that are also quite variable. The extent of DOM utilization also depends upon the duration and temperature of the bioassay experiment. Despite these shortcomings, the bioassay experiment remains the best approach for estimating the bioavailability of DOM. 

Leakage rates are generally expressed in units of p V throughput (see Equation 2.2 and comments). Mass flow rate (Equation 2.1) and molar flow rates (Equation 2.4) can also be used. Conversion factors for leak rates (qpV leak) and mass flow rates are often given for gases in their standard states (pn, Tn). In practice, the difference between room temperature and Tn is not significant when compared to the uncertainties that can occur in the measurement of leakage. 

The conversion factor for cubic feet to cub ic meters is normally 35.31. However, SCF is measured at 21.1 °C and Nm3 is measured at 0°C. Therefore the conversion factor must be adjusted for temperature. All values are rounded to the nearest four or five significant figures. Gas values are expressed in the stable hydrogen condition 75% ortho, 25% para 4I. 

Discussion of the dipolar relaxation involves two issues first, the average dipolar mobility at a given temperature and degree of conversion, as measured by the frequency of the maximum in the loss factor fmax (or by its reciprocal, the typical dipolar relaxation time xd), and, second, the detailed distribution of relaxation times as measured by the frequency dependence of the permittivity and loss factor. In spite of the clear evidence that the dipolar relaxation is associated with the glass transition... 

The recommended unit for MCD spectroscopy, Aem, is based on the extinction coefficient for differential absorbance of a 1M solution of the solute at a field strength of 1 T. The original 9 ellipicity unit is still sometimes used. The conversion factors are 6 = 32.98 AA, where 9 is expressed in units of mdeg or [0]m = 3298A6m where, [0]m is expressed in units of deg cm -dmol . Room temperature spectral measurements are usually measured in solution, ideally in a solvent which is optically transparent in the 280-1000 nm region. 

The density of a substance is not a fixed, invariant property of the substance its value depends on the pressure and temperature at the time of measurement. For some substances (especially gases and liquids), the volume may be more convenient to measure than the mass, and when the density is known, it provides the conversion factor between volume and mass. For example, near room temperature, the density of liquid benzene (CglTg) is 0.8765 g cm . Suppose that 0.2124 L benzene is measured into a container. The mass of benzene is then the product of the volume and the density ... 

For all the above supported catalyst samples, the activity for benzene conversion was measured at two different temperatures, 200°C and 230°C and is reported in Table-2. For each sample, the activity measured at 200°C is lower than that measured at 230°C. Since hydrogenation of benzene is a reversible and exothermic reaction, it is expected that the conversion will decrease with higher temperature. From Table-1, it is also evident that the conversion at both the temperatures does not follow the metal dispersion sequences. Actually high activity is expected from sample SC-2 having high dispersion of nickel, but here lower activity is obtained. This abnormal result may be explained by considering two factors, one acidity of the catalyst sample and the other, crystallite size of nickel. 

Kirste and Lehnen2 determined the Z average of the square radius of gyration, Rg, z of the long chain, in the limit of zero concentration, using the classical interpolation formula (15.5.3) see also Fig. 15.1. (The more adequate formula (15.5.4) was unknown to them.) In an earlier experiment, they also measured the Z average of the square radius of gyration, °Rg,z< of the same chains in the quasi-Brownian state this is the state in which polydimethyl-siloxane chains are found when dispersed in dilute solution in bromo-cyclohexane at temperature T (29 °C). The authors quoted above obtained °Rg,z — 125.44 nm2, i.e. an equivalent area 5, 2(°/ g,z) = 250.88 nm2. From this value, we get the conversion factor [see (15.2.1)]... 

In DTA it must be remembered that although the ordinate is conventionally labeled AT, the output from the AT thermocouple will in most instances vary with temperature, and the measurement recorded is normally the emf. output, E, [the conversion factor, b, in the equation AT = bE is not constant since b = /(r)]. A similar situation occurs with other sensor systems. 

Because the carbon monoxide content of the gas was so low, approaches to equilibrium could not be calculated accurately for runs at nearly complete conversion and low space velocity. One other factor that also makes this calculation difficult is the presence of a hot spot within the catalyst bed, which indicates that the reaction may occur in a narrow zone. Temperature profiles were measured in selected runs (Figure 8). The gas compositions for these runs correspond to equilibrium at the temperatures measured near the bottom (exit) of the catalyst bed, which is what would be expected. 

A variety of units are used in the literature for thermal properties, and this can be a nuisance when different sets of results have to be compared, or when values from an older publication are being used for ealculations. Prior to the adoption of the SI system, the two most eommon units for thermal conductivity were the cal. cm s C and the BTU in ft h F. There are two units of length in the imperial unit, because area is measured in square feet and thickness in inches, and this inconsistency is a potential pitfall for the unw ary. A self-consistent conductivity unit, the BTU ft h F, is obtained if the temperature gradient is measured in F ft instead of F in. but this is not as common. For diffusivity the e.g.s, unit is the cm s and the imperial unit is the ft h. The SI unit for conductivity is the W niK. and the unit for diffusivity is the m" s. For polymers it is more convenient to use a submultiple of the diffusivity unit, the mm" s. because this eliminates a factor of 10 Conversion factors arc given in Table 1. 

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