The diffusion time measurement of colored gases in closed containers is extremely important for many experiments in chemistry. For example, we used the diffusion time (Δt) of iodine in air –inside a closed container– to calculate the free mean path (λ) of molecules by using the relation λ=(Srms)2/((v)Δt); here, (v) is the average molecular speed of the gas, and Srms can be reasonably estimated to be one-half of the predetermine height that the gas has to reach. The usual method to measure Δt for a vertically upward diffusing gas is by visually estimating its presence at a pre-established height (2Srms). In order to minimize mistakes associated with this method, we designed and built a device around a micro controller (Arduino) to automatically measure Δt. The presence of the gas at a pre-established height is tracked every 0.5 s by automatically measuring the voltage of a light sensor, and the temperature inside the container. This approach minimizes the experimental errors associated with the current methods to measure Δt and the temperature at which diffusion occurs. The device was tested as part of a physical–chemistry experiment that calculates Avogadro’s number. We believe the system is robust enough to be able to measure the diffusion time of other colored gases, by simply applying a few programming changes to the micro controller device.

Measuring the time diffusion of a colored gas in a small enclosed container

251st National Meeting (2016)

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