The Density and Transition Points of the «-Paraffin Hydrocarbons 179 ing to 8.20 N in sodium hydroxide and 6.92 N in from the dihydrate to anhydrous sodium iodide, sodium iodide, which point marks the transition Pasadena, Calif.

Sept., 1938 cis-AND trans-DECAHYDRONAPHTHALENE 2125 positive particles than negative ones, In a very short time, less than two minutes, only negative particles remained suspended. The positive particles, which could be seen to settle out very rapidly, apparently had all settled out and left only negatively charged particles. Kruyt and DeKadtl* reported that charcoal activated a t 1000° gave positively charged particles, while charcoal activated at 400' gave negatively charged particles. Kolthoff * observed the same relation between particle charge and temperature of activation. Frampton and Gortner" attempted to prepare positively charged charcoal but did not succeed in doing so; they reported only negatively charged particles for charcoal activated a t 1000". Wie-gandI4 reported that lampblack which was collected by being attracted to a negative plate and, therefore, must have had a positive charge, proved to have a negative charge in an aqueous suspension. Further research regarding the charge of "High Temperature Charcoal" will probably clear up this apparent contradiction in the results on the particle charge for such charcoal.A summary of the data obtained for all the charcoals is given in Table IV. Summary Preferential adsorption from benzene-ethanol solutions by charcoals activated at different(12) H. R. Kruyt and G. S. DeKadt, Kolloidchem. Beiheffe, 32, (13) V. L. Frampton and R. A. Gortner, J . Phys. Chem., 41, 567 (14) W. B. Wiegand, Ind. Eng. Chem., as, 953 (1937). 349 (1931). (1937).temperatures and in different gases shows that charcoal can be changed from extremely organophilic charcoal to charcoal approaching in adsorptive properties the hydrophilic adsorbent, silica.The characteristic S-shaped preferential adsorption curves for a series of increasingly hydrophilic charcoals have been plotted, and the points where these curves cross the X-axis, the X o values, are shown to be a measure of the relative organophilic or hydrophilic nature of the charcoals.The organophilic "high temperature charcoal" (activated at temperatures near 1000°), when suspended in water, gave both positively and negatively charged particles. This charcoal gave acid adsorption but no base adsorption. The less organophilic "medium temperature charcoal" (activated a t temperatures near 4OOo), when suspended in water, gave only negatively charged particles. This charcoal gave base adsorption. The "low temperature charcoal" (activated in a highly oxidizing atmosphere below l5Oo), approaching in adsorptive properties hydrophilic silica, when suspended in water, gave only negative particles. This charcoal showed both acid and base adsorption. ANN ARBOR, MICHIGAN RECEIVED MARCH 17, 1938 2.3.

Considerable work has been done in these Laboratories during the last few years on the properties of the cyclic and dicyclic naphthene hydrocarbons. The present paper deals with viscosity measurements on the cis-and trans-iorms of decahydronaphthalene over a range of temperature from -30 to 180°.naphthalene have been measured from -30 to 180°.2. When log is plotted against 1/T straight lines are not obtained and there is evidence that the m-form undergoes some change at 110°.3. An attempt is made to explain the high values of and £vis, and also the effect of cistrans isomerism on these.

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