G. E. McLaurin

PVT Properties of Water. II. Virial Coefficients in the Range 150°–450°C without Independent Measurement of Vapor Volumes

The equation of state of steam has been determined at 25° intervals from 150° to 450°C by measuring the mass of water injected into a high‐temperature vessel as a function of pressure. The observations have been analyzed by a new method that does not require an independent volume of the vessel and are reported as the second and third virial coefficients and as empirical equations for them. The standard error of the second virial coefficient, taking account of the effects of experimental scatter and of truncation of the virial equation, which are comparable at 450°C, is 3% at 150° and 1% at 450°C. The Stockmayer potential fits the second virial coefficient fairly well, but predicts the wrong form for the third.

Virial Coefficients of Methanol from 150 to 300°C and Polymerization in the Vapor

The second and third virial coefficients of methanol have been determined from 150 to 300°C. At most temperatures the estimated standard error of the second is less than 1%. These values of the second virial coefficient are less negative than results in which the third and higher virial coefficients were neglected. The virial coefficients are interpreted in terms of equilibria between monomer, dimer, and trimer; the enthalpies and entropies of dimerization and trimerization are in line with those found for steam.

PVT properties of water - VII. Vapour densities of light and heavy water from 150 to 500°C

The density of both H2O and D2O vapour has been measured to a precision of 0.1-0.3 mmol dm-3 or 2-6 μg cm-3 in the range 150-500°C by injecting known volumes of liquid water into a vessel of known volume. The maximum pressure was kept low enough at each temperature that neither adsorption nor capillary condensation in the screw threads of the pressure vessel contributed significantly to the measurements. The densities were analysed to determine the second and third virial coefficient by least squares. A more accurate estimate of the second virial coefficient was obtained by accepting the value of the third virial coefficient so obtained and extrapolating the apparent second virial coefficient, as obtained from the measured densities and the values of the third coefficient, to zero pressure. The second virial coefficient of D2O vapour is significantly less than that of H2O vapour, no doubt because of the differences of the nuclear zero-point and thermal energies.

Second virial coefficient of helium from 0 to 500°C by the two‐temperature gas‐expansion method

Values of the second virial coefficient of helium have been obtained from 0 to 500°C as a by‐product of the determination of the thermal expansion of stainless steel vessels used for measurements of the density of water. The Burnett method was used, usually with the two vessels at different temperatures. Gas expansions were made both from the low‐temperature vessel to the high and from the high to the low. Truncation problems limit the precision of B2 for one set of measurements but the temperature dependence has been found accurately. The other measurements appear free of significant systematic error.

PVT Properties of Water. III. Virial Coefficients of D2O in the Range 150°–500°C

The equation of state of D2O has been determined at 25° intervals from 150° to 500°C by the methods used previously for H2O in which no measurements of the vapor volume are required. The conditions reproduced those used for H2O, and the results were analyzed to give the differences in the second virial coefficient of D2O and H2O to maximum precision. The enthalpy and energy of dimerization is about 20 cal mole−1 lower for D2O than for H2O, and the entropy of dimerization is about 0.03 cal deg−1·mole−1 lower. These values agree qualitatively with other related evidence; a quantitative comparison is not possible at present because the large effects of the quantization of the intermolecular motions, particularly rotational and vibrational, are not known well enough.

The PVT Properties of Water. IV. Liquid Water in the Range 150-350 degrees C, From Saturation to 1 Kbar

The change of density of liquid water has been measured at 25 K intervals from 150 to 350 °C and at 60 bar intervals from near saturation, with the apparatus previously used below 150 °C. The precision falls from ca. 10/106 along isotherms at 150 °C to ca. 100/106 at 350 °C, because of the uncertainties of the thermal expansion of the vessel, which was measured by a gas-expansion method.

Antifreezes act as catalysts for methane hydrate formation from ice.

Contrary to the thermodynamic inhibiting effect of methanol on methane hydrate formation from aqueous phases, hydrate forms quickly at high yield by exposing frozen water-methanol mixtures with methanol concentrations ranging from 0.6-10 wt% to methane gas at pressures from 125 bars at 253 K. Formation rates are some two orders of magnitude greater than those obtained for samples without methanol and conversion of ice is essentially complete. Ammonia has a similar catalytic effect when used in concentrations of 0.3-2.7 wt%. The structure I methane hydrate formed in this manner was characterized by powder X-ray diffraction and Raman spectroscopy. Steps in the possible mechanism of action of methanol were studied with molecular dynamics simulations of the Ih (0001) basal plane exposed to methanol and methane gas. Simulations show that methanol from a surface aqueous layer slowly migrates into the ice lattice. Methane gas is preferentially adsorbed into the aqueous methanol surface layer. Possible consequences of the catalytic methane hydrate formation on hydrate plug formation in gas pipelines, on large scale energy-efficient gas hydrate formation, and in planetary science are discussed.

Refraction halos in the solar system. I. Halos from cubic crystals that may occur in atmospheres in the solar system

It is suggested that halos and other refraction effects caused by crystals of various solids that may occur in their atmospheres might occur on the planets of the solar system and their satellites. The detection of the halos would provide valuable information about the nature and the crystalline form of the solids. The halos caused by the octahedral and cubic crystals of carbon monoxide, carbon dioxide, ice Ic, ammonia, methane, and the structure-I clathrate hydrates of nitrogen, carbon monoxide, carbon dioxide, sulfur dioxide, and methane have been predicted over the range of temperatures that may occur in the atmospheres of the planets.

Single‐crystal EPR study of the thermally accessible 3Bu state of trans‐(CNSSS)22+

(CNSSS)22+(Sb2F11−)2 was successfully doped into single crystals of the isostructural diamagnetic material (CNSNS)22+(Sb2F11−)2 and the EPR spectrum of the thermally accessible electronically excited 3Bu state of the dopant cation was measured as a function of angle in three arbitrary, but crystallographically established, planes of the host crystal. A computer program was used to determine the principal values of g and D, the spin–spin interaction tensor, for the impurity triplet, to locate them within the host lattice and, by inference, to place them on the C2h structure of the trans dication guest. Within experimental error, g and D are coaxial, not a requirement of the dication symmetry. The minimum principal value of g (2.0022) and the intermediate value of D (218 MHz) both lie within less than 2° of the perpendicular to the molecular plane, as expected for a π radical and as required by symmetry. Within the dication plane, the maximum principal values of g (2.0271) and of D (−395 MHz) lie 15° from the CC bond. Classical calculations of the dipolar coupling support these observations and their interpretation in terms of a biradical character of the triplet state in which the unpaired electrons are effectively isolated, one in each ring. Copyright

The PVT properties of water. VI. Deuterium oxide in the range 150-500°C and 0-100 MPa

The density of heavy water has been measured at 11 temperatures from 150 to 500 °C, usually at intervals of 6 MPa but sometimes less, from near saturation to 100 MPa and to a precision of ca. 0.01 % .The H : D and 18O : 16O ratios of the water are 0.000 33 and 0.00590 + 0.00003 respectively.