Browsing by Author "BAIRD, JK"

Now showing 1 - 2 of 2

DIAPHRAGM DIFFUSION CELL - A CLOSED FORM SOLUTION TO THE TRANSPORT-EQUATION AND ITS APPLICATION TO THE DETERMINATION OF THE CONCENTRATION-DEPENDENCE OF THE HCL-H2O INTERDIFFUSION COEFFICIENT
(1992)
CHEN, JS
;
CLUNIE, JC
;
BAIRD, JK
;
ROSENBERGER, F
;
應用化學系
In a thermodynamically non-ideal solution, the interdiffusion coefficient D(c) of a two-component system is a function of the concentration c. Since the mean concentration cBAR in a diaphragm cell remains constant during interdiffusion, we have found it useful to expand D(c) in a Taylor series about cBAR. After truncating the series and substituting the result into the diaphragm cell transport equation, we obtain a Bernoulli ordinary differential equation, which we solve in closed form. This solution is experimentally tested by determining D(c) from diaphragm cell data which we accumulated on aqueous hydrochloric acid at 25-degrees-C. Our results are in qualitative agreement with those of R. H. Stokes, who obtained D(c) from diaphragm cell data by using a graphical method [J. Am. Chem. Soc. 72, 2243 (1950)].
THEORY OF THE TIME-LAG DIFFUSION METHOD FOR THE CASE OF AN OUTGASSING SOLID
(1993-06-01)
BAIRD, JK
;
CHEN, JS
;
應用化學系
;
Department of Applied Chemistry
In the ordinary application of the time-lag method to the measurement of the diffusion coefficient of a gas passing through a plane sheet of an inert solid, the gas is pressurized on one side of the sheet and evacuated on the other. After decay of transients, the cumulative amount, Q(t), of gas diffused through the sheet in time, t, assumes the ''time-lag'' form, Q(t) = A(t - L). Measurements of the slope, A, and the intercept, L, can be used to determine the diffusion coefficient and the solubility of the gas in the solid. We have rederived this law for the case of a solid that is actively evolving this same gas at an arbitrary rate and have used it to predict the rate of outgassing of the solid upon standing. Practical applications of the theory include radioactive decay of minerals, rejection of plasticizers by plastics, and the decomposition of solid rocket propellants.