Densities Of Dilute Solutions Research Articles

Limiting partial molar volumes of solutions of oleic, linoleic, and linolenic acids in cyclohexane and benzene

High-precision vibration densimetry was used to measure (with an error of less than 5 × 10−6 g/cm3) the density of dilute solutions (0≤ x 2 ≤ 0.01 mole fractions) of oleic, linoleic, and linolenic acids in cyclohexane and benzene at 298.15 K. The limiting $$\bar V_2^\infty $$ and excess V 2 , ∞ partial molar volumes of these C18: n fatty acids in the indicated solvents were calculated. Benzene was demonstrated to selectviely influence the volumetric effects of dissolution (V 2 , ∞ ) of the linoleic (n C=C= 2) and linolenic (n C=C = 3) polyunsaturated acids.

Acoustic and volumetric studies of intermolecular interactions in dilute solutions of methanol in aromatic amines

Limiting partial compressibilities and volumes of methanol in pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine and 2,6-dimethylpyridine were calculated from the experimental speeds of sounds and densities of dilute solutions at 298.15 K. The limiting functions were found to be linearly correlated with the association energies of isolated 1:1 complexes of the pyridine derivatives with water. Those association energies are close to the energies for similar complexes with methanol. The results evidence that ortho effect enhances the ability of pyridines to hydrogen bonding with methanol in the same way as with water. The effect consist in changes of hydrogen bond energy, unspecific interactions with a steric hindrance, e.g. between hydrocarbon tail of the alcohol molecule and the methyl group in the ring, and changes in resonance interactions. Stronger hydrogen bonds cause smaller partial molar compressibilities and volumes of the solute, as well as greater negative enthalpies of solution. Importantly, single molecule of water or methanol forms one hydrogen bond with the proton-accepting solvent.

Ionic dissociation of aqueous hydrobromic acid. V. Estimate from refractive index and density measurements

The refractive index of aqueous hydrobromic acid was measured up to 19.6m at 0.25 and 60°C. The density of dilute solutions, 0.0676 to 2.76m, was measured at 25°C to high accuracy. These and supplementary data from the literature yielded apparent molar volumes and refractivities. The latter showed the shallow maximum at low concentrations (less than 1.5m) and the gentle linear decline with increasing concentrations, characteristic of strong electrolytes up to about 8 m. The abrupt decline of the apparent molar refractivity with increasing concentrations is interpreted in terms of the association of hydrobromic acid. The apparent molar volumes can also be interpreted, though only quantitatively, in these terms. The results are related to the previously obtained proton nmr data, concerning the extent of association.

XXV.—On the Compressibilities of Dilute Solutions of certain Inorganic Salts

The experiments to be described in this communication were undertaken with the purpose of obtaining values of the compressibility of certain salts, the volume of dilute solutions of which is less than the volume of the constituent water. The densities of such solutions, chiefly hydroxides, sulphates, and carbonates, are discussed by MacGregor in a series of papers published in the Transactions of the Royal Society of Canada; and Kohlrausch includes several of them in his paper on the density of dilute solutions.