Ohm's law, Fick's law, and diffusion samplers for gases

In the diffusion sampler, the coefficient of diffusion of a gas in air and the geometry of the tube were treated separately. The diffusional flux through the tube was calculated using JA = D(A/L)c and for electrical current through a conductor I = E/R where I = current (C/s), E = potential difference (V), and R = resistance (ohms). Resistance to diffusional flux was expressed as L/A. The similarities between Fick's law and Ohm's law were concentrated on; a series of NO/sub 2/ samplers were modified. The total resistance to diffusion of the two tubes in series (L/sup 1//A/sup 1/) was calculated from the relationship: (L/sup 1//A/sup 1/ = L/sub 1/-L/sub 2//A/sub 1/ + L/sub 2//A/sub 2/) where L/sub 1/ and A/sub 1/ are length and cross-sectional area of tube 1, and L/sub 2/ and A/sub 2/ are length and cross-sectional area of tube 2. In all cases A/sub 1/ was 0.713 cm/sup 2/, L/sub 1/ was 7.10 cm, and A/sub 2/ was 0.079 cm/sup 2/. The quantities of NO/sub 2/ captured by the samplers in each of three runs were shown as percent of the amount captured by the unaltered (L/sub 2/=O) samplers. Actual quantities of NO/sub 2/ captured and relative diffusional fluxes predicted from tube dimensions are included. Linear regression analysis comparing experimental values with those predicted from A/sup 1//L/sup 1/ gave the following results for runs 1, 2, 3, and average, respectively: slope 0.995, 1.007, 0.993, and 0.999; intercept -0.07, -1.59, 0.06, and -0.52; correlation 0.999 in all cases. Thus, the results fit the theory well within limits of accuracy of the test systems, and demonstrate that diffusional resistances in series, like electrical resistances, are additive. 1 figure, 1 table. (DP)