RANDOM AND SYSTEMATIC-ERRORS IN THERMOPHYSICAL PROPERTY MEASUREMENTS

General procedures are outlined for the simulation and propagation of random and systematic errors in thermophysical property experiments. D ensity second virial coefficients B(T) from sonic velocity and Joule-T homson (J-T) experiments are examined for error propagation where the connecting thermodynamic identity is a differential equation with miss ing boundary conditions. A recent controversy is addressed concerning B(T) at subcritical temperatures for pure hydrocarbon gases from direc t density measurements vs. new sonic velocity data. Sonic velocity res ults are more likely correct with adsorption errors causing the proble m in the density measurements. Two new model consistency tests are dev eloped for checking assumed temperature models in the reduction of son ic velocity and J-T data to B(T). Excellent values of B(T) are then ob tained from either type of data when the original experiments are free of errors. Random errors propagate systematically when the connecting equation is a differential equation. Sonic data must be of high preci sion (+/- 10 ppm) to generate B(T) to +/- 1 cm(3)/mol due to complicat ions in data reduction arising from the temperature model/random error interaction. Except perhaps for adsorption errors, systematic errors in the sonic velocities are unimportant to B(T). J-T data provide prop agation factors near unity with errors in B(T) higher at higher temper ature, unlike sonic velocities.