Properties of molten carboxylates. Part 1.—Electrical conductance and molar volumes of some molten lead and zinc carboxylates

Abstract

The temperature dependences of the molar volumes, densities and electric conductivities of molten lead and zinc carboxylates of even numbered chain length from C6 to CI8 inclusive are reported at temperatures from the melting points to just below the decomposition points. The molar volumes are linear functions of chain length and nearly so of temperature within the interval of measurement. Semilogarithmic plots of specific conductivity against inverse temperature for the zinc soaps are linear and the slopes decrease slightly with increasing chain length, representing enthalpies of about 40 kJ mol-'. A simple model for the system which proposes that the conduction is due to a small concentration of relatively mobile Zn2+ ions is presented.With the lead salts plots of log specific conductivity against inverse temperature show curvature. Attempts to fit the data to the equation K = A exp[ -C/(T-To)]showed non-random deviations. Instead, a dissociation equilibrium in the meit is proposed which reaches completion in the high temperature range. It is proposed that the major current carrier is the lead ion and values of about 15 kJ mol-I are found for its activation energy for mobility. An approximate method is used to estimate A H and AS for the proposed dissociation reaction from the conductivity data. They are found to be about 85 kJ mol-' and 190 J mol-' K-I respectively for all the compounds studied. The high entropy change may indicate considerable aggregation of the undissociated species in the melts.

Short lead(ii) soaps: from weakly fluorescent crystals to strongly phosphorescent and structurally varied vitreous phases. A thermal, structural and spectroscopic study

“…Members with n $ 6 (ref. [21][22][23][24][25][26][27] have been more widely studied because of their interest as mesogens. They present polymesomorphism: an intermediate phase characterized recently as a rotator mesophase, 18,28 followed by a smectic A like (or neat) liquid crystal phase (only members with 6 # n # 12), at a relatively low temperature (around 380 K).…”

“…The shortest members in this study, Pb(C3) 2 and Pb(C4) 2 , 31 show only a melting process to the isotropic liquid (IL) from the crystal phase (SII), and easily form glass states, 27,31 quenched from the isotropic liquid phase (G IL ). In fact, metal acetate systems (pure or their binary mixtures) show a strong tendency to form glasses.…”

Electrical conductance and thermal behaviour of some manganese(II) carboxylates

“…Similar attempts to fit the conductance data of lead and cadmium carboxylates (which also show non-linear Arrhenius plots) to eq. [l] have been unsuccessful (3,4). Instead, a simple dissociation theory has been proposed to explain the conductance behaviour of lead and cadmium carboxylates (3,4).…”

“…[l] have been unsuccessful (3,4). Instead, a simple dissociation theory has been proposed to explain the conductance behaviour of lead and cadmium carboxylates (3,4). Following the model proposed for these bivalent metal carboxylates, it is proposed that manganese carboxylate dissociates according to the scheme where the MnA, and A -ions may be aggregated in the melt.…”

“…The conductance behaviour of these compounds depends crucially on the nature of the metal ion. For example the Arrhenius plots for conductance of sodium and zinc carboxylates (2,3) are linear while those of lead and cadmium (3,4) show curvature. The curvature observed for the lead and cadmium soaps have been interpreted in terms of a simple dissociation equilibrium which is near completion at high temperatures.…”