Transpiration, measurement

Thermal conductivity and thermal transpiration measurements provide two additional methods by which information may be obtained on inelastic molecular collisions. Mason and Monchick [146] have derived an expression for the thermal conductivity X of a polyatomic gas that includes a term having an explicit dependence upon the relaxation rates of the internal degrees of freedom. Their expression can be written [147]... 

Malinauskas and co-workers [204, 205] and also Healy and Storvich [206] have derived rotational collision numbers from thermal transpiration measurements, utilizing the theory developed by Mason and co-workers [149]. Values have been obtained for the gases N2, CO, 02, and C02, up to temperatures of 500°K. Collision numbers were also obtained by Healy and Storvick for H2 at 444° and for CH4 and CF4 at 366°K. The latter three cases present difficulties for this technique, and it could only be ascertained that Zr(H2) is greater than 100. For N2, 02, and C02, the values of Zr obtained were in good agreement with those derived from acoustical methods, except that the increase in Zr with increasing temperature appeared more pronounced for the thermal transpiration method. 

Malinauskas et al. [205] derived a rotational collision number for C02, from thermal transpiration measurements, of 1.9 at a nominal temperature of 504°K. 

C, ebulliometric and gas transpiration measurements, measured range 5 5°C, Biddiscombe... 

This study was undertaken to determine the relationships between the rapid growth of vegetation after fire and the seasonal variations of some physiological factors in resprouts compared with unburnt material. Seasonal photosynthesis and transpiration measurements as well as leaf nitrogen content were conducted during the first post-fire year. 

Sampling Samples of mature leaves of both areas were taken in the winter, spring, summer and autumn of the first post-fire year (1987). Fire had occurred in August 1986. Sampling was always carried out at the same time ( 2 p.m.) to avoid diurnal variations in the parameters. Photosyn- -thesis and transpiration measurements were followed by liquid nitrogen freezing of the leaves and laboratory analysis. 

Galvin and Pritchard (60) obtained J//, = 26 1 kcal/mole from transpiration measurements on Hg(CN)2 over the range 200-300° C. Accepting this value at 25° C, and combining with AHf° [Hg(CN)2, c] = 62.5 kcal/mole (143), gives... 

Kline, J. R., C. F. Jordan, and R. C. Rose. 1972. Transpiration measurement in pines using tritiated water as a tracer. Isot. Radiat. Technol. 9(3) 348-350. 

A recent and promising modification of the transpiration method incorporates levitation heating of the specimen as problems associated with specimen + container reactions are thereby avoided. Thus Svyzahineto/. have combined levitation melting with transpiration measurements, using argon as carrier gas, in determinations of the vapour pressure of iron at temperatures around 2275 K, and Mills and Kinoshita have used... 

This point was taken up by Reynolds in a letter addressed to G. G. Stokes, in the latter s capacity as Secretary of the Royal Society [83]. Reynolds pointed out that Maxwell s theory evaluated the effects of thermal transpiration only in circumstances where they were too small to be measured, and complained that Maxwell had misrepresented his own theoretical treat ment of the phenomenon. However, this incipient controversy never developed... 

During the course of exploratory experimentation involved in the preparation of 8-242pU203, some limited oxygen potential measurements over Pu02-X fluorite phase were made at 1750 and 2050 K. The transpiration method was used for this study because, for a given temperature, the composition of the condensed phase can be fixed by appropriate choice of oxygen potential (via H2/... 

A particularly interesting question which remains unanswered is whether dinuclear photoproducts are produced directly from the photoexcited parent molecule or whether they are formed by reaction of free radicals within the solvent cage. In principle this question can be answered by making time-resolved IR measurements on the molecules in the gas phase, where no solvent cage can interfere. Thus, it may transpire that a full understanding of the photolysis of these dinuclear compounds will require complementary experiments in solution and in the gas phase. 

The most significant issue, the occurrence of periodic spikes in hydrocarbon and CO measurements in the gaseous effluent, will require further testing to identify the cause and provide a remedy for the problem (see Figure 4-3). The committee considers this problem to be very serious. Resolution must be obtained before the transpiring-wall SCWO process can be seriously considered... 

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