Considerations and proposals regarding the determination of the oxygen content of air using steel wool.

Abstract

Steel wool experiment to determine the oxygen content in the atmosphere has been described in many elementary chemistry textbooks, due to it is an extremely simple procedure that gives good results. Just a few grams of steel wool, a graduated cylinder (or cylindrical glass), a water container and a ruler are necessary to check, by means of a simple operation, that the volume percentage of oxygen in the air is approximately 21%. However, the truth is slightly more challenging, since in order to calculate the oxygen content more accurately, the conditions under which the experiment is carried out, namely the relative humidity of the air, the ambient temperature and the atmospheric pressure, must be taken into account. In the present article, the influence of these factors is analysed and a variant of the experiment with a plastic bottle is presented in which, in addition to determining the mole fraction of oxygen in air with an error of less than 5 %, the force exerted by the atmospheric pressure when the chemical reaction takes place in a closed vessel is demonstrated in a rather striking way.