Vapor pressure of ammonia

Cragoe, C. S.; Meyers, Cyril H.; Taylor, Cyril S.

doi:10.6028/nbsscipaper.046

Cited by 11 publications

(15 citation statements)

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“…has been determined in this laboratory by Mr. M. J. Terry from the triple-point to -164"K, and his values could be extrapolated into the supercooled region with sufficient accuracy to give AV, = Vs-VJ. In evaluating (a(A.Y)/aT), it is convenient to use the equation of state in the form of eqn (6),. when Extrapolated values of the second virial coefficient already referred to were used to estimate B' and C'.…”

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Thermodynamics of liquid mixtures of argon and krypton

Davies¹,

Duncan²,

Saville³

et al. 1967

Trans. Faraday Soc.

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The total vapour pressure of liquid mixtures of argon and krypton has been measured over the whole range of composition at 11577°K (the triple-point of krypton) and at 103.94"K from an argon mole fraction of 4 . 4 to unity. The volume increase VE on mixing per mole has also been determined (at 11577°K). The excess Gibbs energy GE of mixing per mole has been evaluated, and for a given mixture is only about half that estimated from earlier experimental studies of this system. For the equimolar solution, GE is 20.06 cal at 11577"K, and 19.71 cal at 103-94°K. VE is negative, and has an unsymmetrical dependence on mole fraction.The experimental @ has been compared with values calculated from statistical theories of solutions. Theories based on the " two-liquid" or "refined average potential" model predict GE values too high by a factor of about 2. The calculated values are relatively little affected by the choice of intermolecular energy parameters or by the precise form of the intermolecular potential adopted. Values calculated on the " three-liquid " or " separate interaction " model are in much closer agreement with experiment. None of the ways of calculating VE at present available is satisfactory when applied to the argon+krypton system. A possible reason for the unsymmetrical variation of VE with composition is briefly considered.Details are given of a simple but efficient low-temperature fractionating column.Experimental studies have been made in this laboratory of the thermodynamic properties of a number of binary liquid systems composed of simple molecules, with the object of obtaining information suitable for testing statistical theories of solution. In all of the systems investigated, however, one or sometimes both of the components has consisted of diatomic molecules or of simple polyatomic molecules like methane. When there has been disagreement between the observed and calculated thermodynamic functions (which has frequently been the case), it has been difficult to know how far this has been because the theoretical treatment makes assumptions which are not necessarily valid when diatomic and polyatomic molecules are involved, as, e.g., that the interaction energy of a pair of molecules is a function only of their separation and not of their mutual orientation, that the pure liquids conform to the law of corresponding states, and that the partition function of a diatomic or polyatomic molecule for rotational degrees of freedom is the same for the pure liquid and for the solution. It has therefore been desirable to study the simplest possible binary liquid mixtures, viz., those consisting of two rare gases. The liquid ranges of the rare gases are such that they limit to two the number of such systems which can be investigated over the whole range of composition, viz., argon + krypton and krypton + xenon. An accurate study of either of these, however, is experimentally more difficult than a similar investigation of the systems already examined, since the vapour pressure of the more volatile component at the...

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Thermodynamics of liquid mixtures of argon and krypton

Davies¹,

Duncan²,

Saville³

et al. 1967

Trans. Faraday Soc.

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“…In comparing the results of different investigators of the specific heats of petroleum fractions, it is apparent that differences exist which cannot be attributed entirely to experimental error and that these data cannot be correlated by any simple relationship to specific gravity and temperature alone, such as proposed by Cragoe (8). However, if these results are compared from the standpoint of the characterization factors of the stocks, it will be noted that the differences of the various investigators follow more or less TLMPUATURC IN ENLI r.wncwmr…”

Section: Specific Heat (Liquid State)mentioning

confidence: 99%

“…On the above basis the following general equation is proposed as an improved correlation of the specific heat data of liquid fractions from varying sources: The coefficient of s in the above equation is similar to that of the Bureau of Standards' equation (8) and is slightly…”

Section: Figlre 5 Hfethod For Estimating Critic4l Pres-sures O F Petmentioning

confidence: 99%

“…From consideration of the data available in 1929 Cragoe (8) concluded that latent heats of vaporization estimated from modifications of Trouton's rule are consistently too high for petrcleum August, 1933 From consideration of the data available in 1929 Cragoe (8) concluded that latent heats of vaporization estimated from modifications of Trouton's rule are consistently too high for petrcleum August, 1933…”

Section: Heat Of S'aporizatioiy At Atmospheric Pressurementioning

confidence: 99%

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Improved Methods for Approximating Critical and Thermal Properties of Petroleum Fractions

Watson¹,

Nelson²

1933

Ind. Eng. Chem.

121

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H E published literature and the files of every petroleum laboratory contain many data on the physical p r o p T erties of petroleum fractions, the value of which is limited by the difficulty of correlating them into relationships of general applicability. Such correlations should permit prediction of difficultly measurable properties from the results of standardized inspections such as the Engler distillation and the specific gravity. I n our present state of knowledge it is necessary to resort to many purely empirical relationships which have no apparent theoretical foundation but are valuable in that they correlate existing data with accuracy and permit its extrapolation with some degree of assurance. The relationships presented below are for the most part of the empirical type based on consideration of the best data available at this time. It is recognized that in some cases they are not entirely Iogical and that in all cases the actual numerical values will be subject to revision as more data are collected. AVERAGE BOILING POINT Several different m e t h o d s of e s t a b l i s h i n g a so-called average boiling point of petroleum f r a c t i o n s have been in m o r e o r l e s s g e n e r a l use.By calculating an integrated a v e r a g e o r d i n a t e of the true boiling point curve, an accurate a v e r a g e boiling point may be o b t a i n e d . This average will be weighted on either a volum e t r i c o r a weight basis, depending on the units in which the distillation curve is plotted. An integrated average of the 100-cc. E n g l e r d i s t i l l a t i o n c u r v e s i m i l a r l y gives a fair approximation to the volumetric a v e r a g e boiling point with a tendency toward higher values than are obtained by averag-, ing a volumetric true boiling point curve.As a basis for the correlation of p h y s i c a l p r o p e r t i e s , part i c u l a r l y the so-called molal p r o p e r t i e s , a volumetrically weighted average boiling point offers a l e s s logical basis than what may be termed the "molal average boiling point." The molal average boiling point is less than the volumetric average because of the fact that the ratio of specific gravity to molecular weight is higher for the low-boiling members of a hydrocarbon series. Thus, in determining the average boiling point from a volumetric distillation curve, the lower boiling fractions should be given increased weighting in proportion to the variation with boiling point of this ratio of specific gravity to molecular weight. I n Figure 1 is presented a curve giving a correction to be subtracted from the volumetric average boiling point of a petroleum fraction in order to obtain an approximation to its molal average boiling point. This correction is expressed as a function of the slope of the 100-cc. Engler distillation curve and becomes zero as the slope of the curve approaches zero, denoting a pure compound. The general form of this curve was derived by plotting the ratio of specific gravity Two new concepts are introduced f o r correlatio...

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“…where is the second virial coefficient. The form chosen for Q was 9 6 Q " we obtain for the entropy, S(p,T) -R[Jtn p + pQpt 9Q/9t] + S°(T), (5) the internal energy, E(p,T) -= RpTt3Q/8t + E°(T), (6) the constant volume heat capacity,…”

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confidence: 99%