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The heat capacity of solid and liquid formic acid has been measured from 15 to 300°K. The melting point is 281.40°K (0°C=273.10°K). The heat of fusion is 3031 cal. mole-1 and the heat of vaporization at 298.10°K is 4754 cal. mole-1. (1 mole=46.0260 grams.) The vapor pressure at 298.10°K is 4.31 cm of mercury. From the third law of thermodynamics and the calorimetric data the entropy has been calculated. To the value obtained from the calorimetric measurements an entropy of R/2 ln 2, due to the random orientation of hydrogen bonds in the solid which has been predicted by Pauling, has been added. This gives 31.51 cal. deg.-1 mole-1 for the entropy of the liquid at 298.10°K and 47.46 for the entropy of 46.0260 grams of gas, P=4.31 cm, in equilibrium with the liquid at 298.10°K. These are the values that should be used in thermodynamic calculations.

The nature of the uniform field breakdown in argon has been investigated by measuring the formative time lags of breakdown as a function of overvoltage (from about 5 to 100 percent), pressure (150-to 700-mm Hg) and electrode separation (0.3 to 3.0 cm). Formative time lags in argon at a given percent overvoltage are very long compared to the values previously obtained in air and nitrogen. For most values of pressure and electrode separation studied in argon, an overvoltage of 100 percent must be applied before the time lags decrease to the order of ljusec. The results in argon (like those in air and nitrogen) indicate a Townsend buildup before breakdown. For the range of variables studied in argon, the data cannot be accounted for satisfactorily by buildup as a result of metastable action at the cathode, positive ion bombardment of the cathode, or photoelectric emission from the cathode by photons crossing the gap with a velocity close to c. There is a possibility that the results may be explained by a photoelectric effect at the cathode if delays are introduced due to the diffusion of resonance radiation; this conjecture remains to be verified. At this time the positive identification of the effective secondary mechanism in the breakdown of argon cannot be made. The present results indicate the universality of the Townsend buildup before breakdown, but the buildup may proceed by different mechanisms in different gases.

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