Measurements of vapor pressures and boiling points, over the range 47 to 780 millimeters of mercury and above ah>out 12° C, were made on 52 purified hydrocarbons. The apparatus consisted of an electricaUy heated boiler, a vapor space with a vertical reentrant tube containing a platinum thermometer having a resistance of 25 ohms, and a condenser. Measurements of the temperature of the liquid-vapor equilibrium were made at 20 fixed pressures maintained automatically. The values of the fixed pressures were determined by calibration of the apparatus with water by using the vapor pressure-temperature tables prepared at the National Bureau of Standards.The experimental data on the hydrocarbons were correlated, the method of least squares being used, with the three-constant Antoine equation for vapor pressures, log P=A-B/(C+t) or t=B/(A-Iog P)-C. Experimental data, together with the values of the three constants of the Antoine equation, applicable over the range of measurement, are reported for 30 paraffin, 4 alkylcyclopentane, 10 alkylcyclohexane, and 8 alkylbenzene hydrocarbons.

Values are presented for the following thermodynamic properties: The heatcontent function, (HO -Ho 0) / T, the free-energy function, (FO -Ho 0) / T,lthe entropy, So, the heat content, HO-Hoo, and the heat capacity, C" 0, for O2 (gas) to 5,000 oK, Hz (gas) to 5,000 oK, H20 (gas) to 3,000 oK, N2 (gas) to 5,000 oK, C (solid, graphite) to 1,500 oK, C (solid, diamond) to 1,200 oK, CO (gas) to 5,000 oK, CO2 (gas) to 3,500 oK, and CH. (gas) to 1,500 oK; the standard entropy, So, for H 2 0 (liq) at

No abstract

A method is described for determining analyt ically OJ' graphically, from appropriate time-temperature freezin g and melting curves obtained 011 hydrocarbons, the freezing point of a given substance, and within certain wide limits, the freezi ng point of that substance for zero impuri ty (liq uid-solublc, solid-insoluble).

It is shown t hat in normal coo rdi nate calculati ons of t he vibrations of moleculcs it is so metimes adva ntagco lls to calculatc the kin etic-e ncrgy matrix, r at her t ha n t he l'?ciprocal k inetic-energy m atri x. E xp li cit formulas are give n fo r t he elemen ts of the klllCtlC-energy matrix. Illustrative calculalions are given for p ropane, toluene, a nd ethy lbenzene . A se mi e mpiri cal assig nm e nt of t he v ibration frequencies of ethylbe nezene is made on t he basis of these calculations and the spectroscopi c data.