This document provides instructions for determining the amount of dissolved oxygen in a water sample using an iodometric titration method. Key steps include adding excess manganese sulfate and potassium iodide to the water sample, precipitating the manganese ions with sodium hydroxide, dissolving the precipitate with sulfuric acid to liberate oxygen that oxidizes iodide to iodine, and titrating the iodine with a standardized sodium thiosulfate solution. Dissolved oxygen levels between 5-8 mg/L are considered good for aquatic life. The document also lists chemicals needed, apparatus, reaction equations, procedure, and questions about the significance and method.