merize seriously during a ten-hour period until 275°was reached.The constants of an equation of state of gaseous isobutene were determined from the data up to the critical density; and the values of the second virial coefficients determined from the experimental data are given from 150 to 275°.

No abstract

No abstract

Several accurate experimental determinations of the heat capacities of gaseous ethane3p4z5 and propane6 at, near, or below room temperature have been made and the problem of the hindered potentials in the two gases has been studied from a number of standpoints. I t seemed desirable to extend the experimental heat capacity measurements over as wide a temperature range as possible in order to test the previously deterniined heights and shape of these barriers and the vibrational assignment chosen for these two molecules.The general method of determining gaseous heat capacities as developed by Bennewitz and S c h~l z e ,~ was adopted for this investigation; certain modifications, to be described in the next section, were made in the interest of greater accuracy and ease of operation. With this adiabatic flow calorimeter, heat capacities were determined over the temperature range, 84--70O0K. with an accuracy of a t least one part in 100. Design and Operation of ApparatusIn the method of Bennewitz and Schulze,? the heat capacity of the gas is obtained in terms of the electrical energy input of a heater which is necessary to maintain a linear temperature gradient along a thin-walled Pyrex tube, placed between two massive brass blocks maintained a t a temperature difference, AT, through which a stream of the gas is flowing with a known velocity.For the general design of the apparatus, the description given by Bennewitz and Schulze? may be consulted. Only changes in design which facilitated the ready assembly of the apparatus, which increased the sensitivity of the calorimeter, and which insured a more convenient manipulation and a more complete drying of the gases will be discussed here.The brass blocks of the apparatus were connected by four symmetrically placed Pyrex glass rods cemented into place by means of sodium silicate and these blocks were bound together by means of a small split brass cylinder secured by several small screws. These blocks were bored off-center (1) Constructed from a portion of a thesis presented to the Graduate Faculty of the University of Texas by Benjamin P. Dailey in partial fulfillment of the requirements for the degree of Doctor of Philosophy, August, 1 Y U (2) Present address: W. D. R .

No abstract