Norman O. Smith

Solubility of natural gases in aqueous salt solutions—I: Liquidus surfaces in the system CH4-H2O-NaCl2-CaCl2 at room temperatures and at pressures below 1000 psia

The solubility of methane in water, in aqueous solutions of sodium chloride, calcium chloride, and both sodium and calcium chloride has been determined at room temperatures and at pressures up to 1000 psia by the pressure decline method. The results for water agree with previous published values, but the solubilities in the salt solutions are considerably higher. The data obtained, augmented by other solubility figures from the literature, permit the construction of the liquidus surfaces in the tetrahedral phase model for the system CH4-H2O-NaCl-CaCl2 at fixed temperature and pressure. An orthogonal projection of these surfaces is presented.

Solubility of natural gases in aqueous salt solutions—II: Nitrogen in aqueous NaCl, CaCl2, Na2SO4 and MgSO4 at room temperatures and at pressures below 1000 psia

Abstract The solubility of nitrogen in brine at room temperatures and at pressures below 1000 psia was determined in an effort to understand better the processes controlling intrastratal fluid flow. Solubilities were measured in water, aqueous NaCl, CaCl 2 , Na 2 SO 4 and MgSO 4 solutions by the pressure decline method. The results for water are in satisfactory agreement with those of other investigators. Previously published solubilities for salt solutions are limited to NaCl at low pressure, and are considerably smaller than those found in the present study. The data were used to estimate the invariant liquid compositions for the quaternary system N 2 -H 2 O-NaCl-CaCl 2 at 30°C and a representative pressure of 500 psia, from which the liquidus surfaces in the tetrahedral phase model may be constructed.

Sublimation pressures of solid solutions III. NH4Cl + NH4Br

The total sublimation pressures of ammonium chloride, ammonium bromide, and of ten solid solutions of these salts, covering the entire composition range, have been measured by a static method from 250 to 320°C. The results were fitted to ln P = A − BT −1 + C ln T . The isothermal variation of total pressure with composition indicates that the solids deviate positively from Raoults law. The differences between the “second-law” and “third-law” values for the enthalpy of sublimation for the pure chloride and pure bromide are discussed. Results are presented for the variation with composition, at 550 K, of the enthalpy of sublimation, uncorrected for possible incomplete dissociation in the gas phase.

Sublimation pressures of solid solutions IV. (C6H5)4Si + (C6H5)4Sn, (C6H5)4Si + (C6H5)4Pb, and NH4Br + KBr

The sublimation pressures of the solid solutions in the binary systems (C6H5)4Si + (C6H5)4Sn, (C6H5)4Si + (C6H5)4Pb, and NH4Br + KBr, which show complete miscibility in the solid state, were measured as a function of composition from 453 to 488 K for the tetraphenylmetal mixtures using a differential manometer, and from 543 to 593 K for the third mixture using an isoteniscope. Only (C6H5)4Si and NH4Br are volatile at these temperatures. The results were fitted to ln p = A − BT−1 for the first two mixtures, and to ln p = A − BT−1 + C ln T for the third, and partial enthalpies of sublimation of the volatile component were obtained. The tetraphenylmetal mixtures are nearly ideal. Activity coefficients of both components in NH4Br + KBr were computed assuming the vapor to be completely dissociated into NH3 and HBr. This mixture shows positive deviations from ideality for both components. The results are discussed qualitatively in terms of lattice dimensions, and the effect of possible incomplete dissociation of NH4Br(g) is described.

Thermodynamics of ionic solid solutions. A new treatment of existing distribution data

Excess amounts of two isomorphous salts, which differ with respect to only one ion (the exchanging ions), added to water and equilibrated produce an aqueous solution of the two salts and a solid solution of one salt in the other. The ratio of the two salts in the liquid phase is, in general, different from that in the coexisting solid. Data for twenty-nine such systems, including pairs of double salts (alums and picromerites), and pairs of simple salts, at or near 25°C, have been reviewed. By making the plausible assumption that the activity coefficients of the exchanging ions in the liquid phase are equal, it has been possible to derive the activity coefficients of the salts in the solid phase in addition to the thermodynamic equilibrium constants for the distributions. The interpretation of the data is compared with that of an earlier paper which drew different conclusions and was based on what is shown to be an erroneous premise. Solid solutions of alums are found, for the most part, to be ideal or nearly so. Of nine picromerite solid solutions containing sulfate as the only anion, seven pairs deviate positively from ideality, one deviates negatively, and one shows both positive and negative deviations. Three other picromerite pairs involving exchange of sulfate, selenate, and chromate ions, show only negative deviations. For the pairs [(NH4)2,K2]SO4, (NH4,K)Cl, Ag(Cl,Br), K(Br,Cl), Rb(Br,Cl), (Rb,K)Br, and (Rb,K)Cl the deviations are positive; those for Pb(Cl,Br)2 are negative, and those for Ba(ClO3)2·H2O are both positive and negative. Independent supporting evidence for some of the conclusions is presented.

Thermodynamics of ionic solid solutions: II. Discontinuous series: A new treatment of existing distribution data

A method of finding the activity coefficients of salts, anhydrous or hydrated, in binary solid solutions, described in an earlier paper as it applies to continuous series, has been applied to discontinuous series. The salts must differ with respect to only one ion. The method requires isothermal distribution data for equilibria between liquid (aqueous) and solid solutions in the ternary system consisting of the two salts and water. The following salt pairs were used for illustration: K(I/Br) at 0, 15, 25, 35, and 50°C., (NH4/K)SCN at 0, 30, 60, and 90°C., (K/Tl)C103 at 10°C., and (NH4/K)SO3NH2, (NH4/K)Br, (Mg/Co)SO4-7H2O, and (Mn/Cu) SO4.n H2O-all at 25°C. Two kinds of behavior were noted and treated differently: systems in which the two series have the same, and those in which they have different crystal lattices. For two salts, A and B, which have the same lattice, and whose rational activity coefficients, fA and fB, can be described by 2-suffix Margules equations (regular solutions), lnfA=BsxB2 and lnfB=BsxA2 to be partially miscible, Bs>2, but this requirement does not apply if the lattices are different. In each series, distribution constants for the equilibria were also determined. Where possible, the calculated activities of the salts or the Gibbs excess energies of the solid solutions were compared with values reported by others who determined them by other methods. All the salt pairs studied show slight or strong positive deviations from ideality.

Competition among aromatic guests for the host tetrakis(4-methylpyridine)nickel(II) isothiocyanate and a basis for the observed selectivity

In continuing attempts to determine the basis for the selectivity shown by the host Ni(4-mepy)4(NCS)2 (1) toward aromatic guests, distribution data between solid and liquid phases are reported for seven ternary systems at room temperature. These consist of1,p-xylene, and each of the following:p-bromotoluene,p-chlorotoluene,p-fluorotoluene,p-dichlorobenzene, benzene, and 4-methylpyridine, as well as the system1-p-chlorotoluene-p-dichlorobenzene. The results, as well as those for five systems already published, have been reviewed and a hierarchy of selectivity developed. After correcting the observed selectivity for inequality of guest vapour pressures the order of decreasing preference is found to bep-bromotoluene >p-dichlorobenzene >p-chlorotoluene > deuterated and protiatedp-xylenes > ethylbenzene > 4-methylpyridine >p-fluorotoluene > toluene > benzene. With the exception of 4-methylpyridine, this is the same as the order of decreasing van der Waals length of the guest molecule and, where known, the order of enthalpy of inclusion. Although longer guest molecules and those with higher vapour pressures are favoured in selectivity, guests with longer molecules are likely to have lower vapour pressures. The activity coefficients of the included guests are calculated assuming that the liquid phases follow Raoults law.

Crystallographic Studies of NH4Cl-NH4Br Solid Solutions

Both ammonium chloride and ammonium bromide undergo a transition, with rise in temperature, from an interpenetrating simple cubic (II) to a face-centered cubic (I) lattice at 183 and 137°C, respectively, and both the low- and high-temperature forms give a complete series of solid solutions. We have determined the lattice constants of the high-temperature solids at about 250° as a function of composition, and redetermined the lattice constants of the low-temperature solids at room temperature. The solutions were made by crystallization from water, followed by stirring in contact with mother liquor for at least three weeks at room temperature. Measurements were made with a Norelco-Philips diffractometer and recorder, with Cu K α radiation. For the high-temperature work, a simple, inexpensive heating apparatus was developed. The only previous data reported for the high-temperature forms are the lattice constants of the pure components given by Bartlett and Langmuir.13

Thermodynamics of ionic solid solutions: III. An addendum

In two earlier papers (C.A. 117:259320(1;121:19411y) the activity coefficients of the salts in binary solid solutions at 25‡C for 38 salt pairs, in which the members of each pair differ with respect to only one kind of ion, were determined. While the activity data are correct, the conclusions regarding deviations from ideality for eight of these pairs, namely those in which there are two moles of replaceable ion per mole of salt, require modification in order to be consistent with ideal entropies of mixing. By changing the formulation of the component salts to one-half of what is usual, the inconsistencies disappear. This half-mole approach, applied to the salt pairs CU1/2(NH4/K)SO4-3H2O, Mg1/2NH4(SO4/ CrO4)-3H2O, Mg1/2NH4(SeO4/SO4)-3H4O, Mg1/2NH4(SeO4/CrO4)-3H4O, Mg1/2 (K/NH4)SeO4-3H2O, (NH4/K)(SO4)1/2, and Ba1/2(ClO3/BrO3)-1/2 H2O shows that these solid solutions exhibit positive, not negative, deviations from ideality at 25‡C. Only the system Pb1/2(C1/Br) still deviates negatively.

Thermodynamic analysis of equilibria between binary liquid and solid solutions in ternary systems. Application to systems in which two guests compete for sites in the same host, tetrakis(4-methylpyridine)nickel(II) isothiocyanate

A thermodynamic analysis is presented of the equilibria between liquid solutions of guest A in guest B and solid solutions of HA in HB, where HA and HB are isomorphous 1:1 compounds of these guests with the host H. (The treatment is applicable whether or not HA and HB are inclusion compounds.) The mole ratio of A to B in the liquid,R1, is generally different from the same ratio in the solid,Rs. Data on many systems have indicated a linear relation between InR1, and InRs, but to date no theoretical basis has been forthcoming. The present analysis shows that this relation is usually sigmoidal in shape but, with certain restrictions, is nearly linear. The slope and intercept are interpreted in terms of the equilibrium constant for the displacement of A from HA by B and the deviations from ideality in the liquid and solid phases. If the deviations from ideality in the liquid phase are known or can be estimated, those for the solid phase can be determined, and thermodynamic equilibrium constants and standard free energy changes for the displacement of A by B calculated. These methods were applied to available data for the following pairs of guests with the host Ni(4-mepy)4(NCS)2:p-xylene with each ofp-dibromobenzenp-xylene-d6,p-xylene-d10,p-bromotoluene,p-chlorotoluene,p-dichlorobenzene,p-fluorotoluene, ethylbenzene, toluene, and benzene, and the pairsp-dichlorobenzene/p-chlorotoluene and ethylbenzene/ toluene.