Measurement of K_La in a bioreactor can be carried out by sodium sulfite oxidation method, that is, based on the oxidation of sodium sulfite to sodium sulfate in the presence of a catalyst (Cu⁺⁺ or Co⁺⁺). In a typical experiment, a laboratory fermenter was filled with 5 liter of 0.5 M sodium sulfite solution containing 0.003 M Cu⁺⁺ ions and the air was sparged in. After 10 min, the air flow was stopped and a 10 mL sample was taken and titrated. The concentration of sodium sulfite in the sample was found to be 0.20 M. The oxygen uptake rate for this aerated system will work out to be