Abstract
The preparation and standardisation of solutions of oxygen are rendered difficult by the normally gaseous nature of this substance and thus special precautions are necessary to ensure accurate and reproducible results. The preparation of oxygen solutions may involve both aeration and deaeration and various techniques are available for the purpose, depending on the oxygen concentration required and the efficiency demanded of the process. For the standardisation of solutions of oxygen a wide range of methods is available involving many different analytical techniques. Three methods have been developed and used in this work, two being chemical and the third gasometric. The chemical methods both include a final potentiometric titration which is carried out automatically using apparatus designed and built for the purpose. A feature of these titrations is the use of a glass electrode as the reference electrode. The standardised solutions of oxygen are studied by polarographic techniques, three different types of instrument being used to obtain data on the degree of reversibility of oxygen at the dropping mercury electrode. It is shown that the first reduction takes place reversibly, while the second is virtually irreversible. Measurements are also made of the concentration-current relationship for each reduction wave. The results obtained are shown to indicate a disproportionation reaction. Measurements are made of the half-wave potentials of each of the two reductions of oxygen, and also of the temperature coefficient of its diffusion current. The diffusion coefficient of oxygen in potassium chloride solution is calculated from the polarographic data.