Precise pressure volume temperature measurements on corrosive gases are dependent on a sensitive yet rugged pressure transducer. A prototype which fulfills the requirements was developed and thoroughly tested. The transducer is a null type instrument and employs a stretched diaphragm, 0.001 in. thick and 1 in. in diameter. A small pressure unbalance displaces the diaphragm and changes the capacitance between the diaphragm and an electrically insulated plate spaced 0.001 in. apart (for ** f). Spherical concave backing surfaces support the diaphragm when excessive pressures are applied and prevent the stresses within the diaphragm from exceeding the elastic limit. Over a temperature range from 25 to 200 ** f and at pressures up to 250 atm, an overload of 300 psi, applied for a period of one day, results in an uncertainty in the pressure of, at most, one millimeter of mercury.

A 6 -- year study of the transport properties of air at elevated temperatures has been completed. This project was carried out under sponsorship of the Ballistic Missile Division of the Air Research and Development Command, U. S. Air Force, and had as its goal the investigation of the transport by diffusion of the heat energy of chemical binding. A significant effect discovered during the study is the existence of Prandtl numbers reaching values of more than unity in the nitrogen dissociation region. Another effect discovered is the large coefficient of thermal diffusion tending to separate nitrogen from the oxygen when temperature differences straddling the nitrogen dissociation region are present. The results of the study, based on collision integrals computed from the latest critically evaluated data on intermolecular forces in air, will be reported in the form of a table of viscosity, thermal conductivity, thermal diffusion, and diffusion coefficients at temperatures of 1000 to 10000 ** f and of logarithm of pressure in atmospheres from ** f to ** f times normal density.