AbstractThe kinetics of the batch‐wise liquid‐phase oxidation of ferrous sulfate by the organismThiobacillus ferrooxidanshas been studied over a range of temperatures from 20°C to 31°C and in the presence of an abundant supply of oxygen, carbon dioxide, and other nutrients.The rate of oxidation was found to be accurately described by the equation\documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{dS}}{{dt}} = \frac{{\mu _m SX}}{{Y(K + S)}} $$\end{document}wheret= time hr,S= concentration of ferrous ions g Fe++/1., μm= maximum specific growth rate of bacteria, hr−1.Y= mass of bacteria produced per gram of iron oxidized g/g,K= saturation constant, g Fe++/l., andX= concentration of bacteria g/1.The value for the maximum specific growth rate, μm, was found to vary from 0.12 hr−1at 20°C to 0.20 hr−1at 31°C, while the value for the saturation constantKvaried randomly between 1 and 2 g/1.A method has also been described which permitted evaluation of the relevant rate constants μmandKwithout direct knowledge of the bacterial population. This method was found to yield values of μmandKwhich agreed with values determined accurately by a statistical regression analysis of the