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An improved technique has been developed for the determination of the electrical conductivity of reactive molten salts and has been applied to cryolite. The method employs a platinum cell with two concentric hemispherical electrodes. This cell is maintained a fixed distance below the surface of the molten salt which is held in a larger platinum container. Errors from lead resistance have been eliminated by measuring with a Kelvin double bridge (Thomson bridge) and polarization difficulties have been minimized by extrapolation of the nearly linear plot of resistance vs. frequency−1/2 to infinite frequency. Conductivities of molten potassium chloride, sodium chloride, and lithium cloride were determined with a quartz dip‐cell. Best values for the conductivities (ohm−1cm−1) at 1000°C were: cryolite 2.80; potassium chloride 2.65; sodium chloride 4.17; and lithium chloride at 700°C, 6.14. Densities (g/ml), measured by a platinum sinker, were found to follow these equations from the melting points to 1080°C : potassium chloride 1.964–0.574ċ10−3 t; sodium chloride 1.969–0.524ċ10−3 t; cryolite 3.032–0.937ċ10−3 t. The logarithm of equivalent conductance (A) changed linearly with reciprocal absolute temperature (T). Best values for the activation energy for conductance (kcal/mole) (calculated as 2.303 times 1.986 cal/mole deg times slope of log A vs. 1/T) were: cryolite 4.48; potassium chloride 3.32; sodium chloride 3.04; lithium chloride 1.70. Maintaining the fused cryolite in contact with an atmosphere of argon as compared with room air had a negligible effect upon the measured conductivity values for cryolite.

The electrical conductivities at 1000°C, expressed as per cent of the cryolite value, for cryolite containing 10 weight per cent of the following substances are: sodium fluoride 112, calcium fluoride 96, aluminum fluoride 91, and alumina 83. For pure sodium fluoride at 1000°C, conductivity is 5.52 ohm−1cm−1, compared to 2.80 ohm−1cm−1 for cryolite. Molar conductance decreases linearly with mole per cent sodium fluoride, aluminum fluoride, alumina, or calcium fluoride addition to cryolite. The activation energy for conductance, calculated from a plot of the Arrhenius equation, is about 4.3 kcal/mole for the systems of cryolite with sodium fluoride, aluminum fluoride, and alumina, as well as for pure sodium fluoride, but is slightly higher for the cryolite‐calcium fluoride system. This value agrees reasonably with the 4.48 kcal/mole for pure chryolite. Densities in these systems change linearly with temperature, that for pure sodium fluoride following the equation 2.567–0.610×10−3 t . The stability of the complex normalNaF·×Na3AlF6 is indicated by a density maximum.

THE deposition of active agents onto adsorbentshas been employed widely to provide catalysts of increased activity, improved stability, greater selectivity, more convenient physical form, and lower cost (11). The development of a simple method for measuring surface areas of porous materials (1) provided a basis for correlating information on the action of adsorbents in this application. This work was undertaken to examine the relation of adsorbent area to catalyst activity for molybdena impregnated onto activated alumina as a catalyst for the dehydrocyclization of n-heptane to toluene. This reaction was reported with a variety of catalysts prepared in diverse manners on a number of supports (4, 5, 7, 9, 14, 15). investigation of the reaction mechanism indicates that an initial dehydrogenation is followed by cyclization and further dehydrogenation (S, 17, 18). Carbon skeleton rearrangement can take olace on a chromia-alumina catalyst (10). MATERIALS, APPARATUS, AND ANALYSISThe activated aluminas were products of the Aluminum Ore Company. The activated alumina F series analyzed: 2% loss on ignition, 0.1% Na20, 0.1% Si02, 0.05% FeA, and 0.7% Cl.The activated alumina H series analyzed: 4% loss on ignition, 0.1% Na»0, 7% Si02, 0.2% Fe203, '.3% CaO, 0.2% MgO, and 0.3% S03. Activated aluminas of the H series have one and a half to three times the surface area and pore volume, and more uniform pore widths as determined by sorption, than do those of the F series. Molybdena was obtained as Baker's Analyzed ammonium molybdate: 83% MoOs, 0.01% SO,, all other reported impurities less than 0.01%. Ammonia was Baker's Analyzed (meeting A.C.S. standards). The n-heptane, supplied by Westvaco Chlorine Products Company, had boiling point 98,42 °C., freezing point -90.65°C ., d^°0 .68371 gram per ml., and 21.38766. Tank hydrogen passed over hot copper and dried with activated alumina was used for catalyst reduction.Catalysts were prepared as follows: Ammonium paramolybdate was dissolved in distilled water (0.5 ml. per gram of alumina in the completed catalyst), and the quantity of concentrated ammonia necessary to convert the paramolybdate to the normal molybdate was added. The solution was boiled and the alumina added immediately wdth vigorous stirring. The excess water was removed by drying at 70-90°C. under overhead heat, with occasional stirring. "When the alumina appeared dry, in 4-6 hours, the sample was calcined 16 hours at 500°C.