M.L McGlashan

An improved dilution dilatometer for measurements of excess volumes

Abstract A new design of tilting dilution dilatometer is described. It is easier to calibrate, and easier to load and operate, than previous designs, and has two advantages. No liquid passes through a greased (or any) tap and no tap is opened or closed throughout a series of dilution measurements. There is no possibility of error from diffusion of one liquid into the other, the liquids always being separated by mercury. The new dilatometer has been used to make a series of measurements of the molar excess volume of benzene + cyclohexane at 298.15 K; the results compare well with those of previous measurements.

Thermophysical properties of alkanes from speeds of sound determined using a spherical resonator I. Apparatus, acoustic model, and results for dimethylpropane

Abstract The speed of sound in dimethylpropane between 250 and 323.15 K has been obtained from measurements of the frequencies of the radial modes of a spherical acoustic resonator; the acoustic model and the apparatus are described briefly. The radius of the resonator was obtained from the speed of sound in argon. Perfect-gas heat capacities and second and third acoustic virial coefficients for dimethylpropane have been calculated from the results, and estimates are given for the second and third ( p , V m , T ) virial coefficients.

The Temperature-Jump Effect and the Theory of the Thermal Boundary Layer for a Spherical Resonator. Speeds of Sound in Argon at 273.16K

The theory of the thermal boundary layer at the walls of a spherical acoustic resonator is discussed in detail. For gases at low pressures, the temperature-jump effect is found to make a significant contribution to the resonance frequencies of the radial modes but not to their acoustic losses. Experimental results are reported for argon at 273.16 K and pressures between 15 and 248 kPa, and compared with the theory. These were obtained using the four radial modes with lowest frequency of a spherical resonator with a radius of 60 mm. The thermal accommodation coefficient between argon and the aluminium wall of the resonator was found to be (0.84 ± 0.05). The results suggest that a determination of the gas constant with a fractional imprecision of 1 × 10-5 or better should be possible using a spherical acoustic resonator.

Thermophysical properties of alkanes from speeds of sound determined using a spherical resonator 2. n-Butane

Abstract The speed of sound in gaseous butane between 250 and 320 K has been obtained from measurements of the frequencies of the radial modes of a spherical acoustic resonator. Perfect-gas heat capacities and second and third acoustic virial coefficients have been calculated from the results. Methods of calculating (p, Vm, T) virial coefficients from acoustic results are discussed in detail and values for butane are given.

The international temperature scale of 1990 (ITS-90)

Abstract The International Temperature Scale of 1990 (ITS-90) is introduced, is operationally defined for different ranges from 0.65 K upwards in terms of vapour-pressure thermometry, gas thermometry, platinum resistance thermometry, and optical pyrometry, and is compared numerically and graphically with the IPTS-68 (T68), and also numerically with the EPT-76 (T76).

Chiral discrimination in liquids II. Excess molar enthalpies of {(1 − x)A+ + xA−}, where A denotes fenchone or α-methylbenzylamine

Abstract Small but definite chiral discrimination is revealed by measurements of the excess molar enthalpy H m E of the liquid (+) and (−) enantiomers of fenchone and of α-methylbenzylamine. For fenchone H m E is negative at 303.11 K; for α-methylbenzylamine H m E is positive at 303.11 K and though still positive at 313.11 K appears to be about to change sign and become negative at temperatures above approximately 340 K.

The vapour pressure from 451 K to the critical temperature, and the critical temperature and critical pressure, of cyclohexane

Abstract The vapour pressure of cyclohexane has been measured from 451 K to the critical temperature, and the critical temperature, T 68 c = (553.64 ± 0.03) K, and critical pressure, p c = (4075 ± 2) kPa, have been obtained. The results are compared with those of previous workers both within the same temperature range and at lower temperatures.

Amount of Substance and the mole

The use of the term amount of substance of an elementary entity is expounded. Methods of measurement of the ratio of two amounts of substance are described. The SI unit of amount of substance, the mole, is introduced. Quantities involving amount of substance, including molar mass, molar quantities in general, the Avogadro constant, the molar gas constant, and the Faraday constant, are defined. An historical account is given of the notion of amount of substance and of the unit mole. Some personal views are advanced about the desirability of a new name for amount of substance and for derived quantities.

The vapour pressure, orthobaric volumes, and critical constants of tetramethylsilane

Abstract The vapour pressure and orthobaric molar volumes of tetramethylsilane have been messured from 373 K to the critical temperature, and the critical temperature (IPTS-68: T o = 448.64 K ), critical pressure ( p c = 2821 kPa ), and critical molar volume ( V m c = 361 cm 3 mol −1 ) have been determined.

The (liquid + liquid) critical state of (cyxlohexane + methanol) IV. (T, x)p coexistence curve and the slope of the critical line

Abstract The (T, x)p coexistence curve of {xc-C6H12+(1−x)CH3OH} has been measured within 1.3 K of the critical temperature (Tc ≈ 318.4 K) at constant atmospheric pressure. In addition an estimate of ( ∂T c ∂p ) x = x c near atmospheric pressure has been obtained. The results have been analysed to determine the critical amplitude of the coexistence curve when the critical exponent β is fixed at the value calculated from theory. In addition, it has been shown that mole fraction is a better order parameter for this mixture than mass fraction and that the first symmetric Wegner-correction term is just significant.