Further Improvement in Preparation Experiment of Ferrous Hydroxide
LIU Xi-Peng1, CHEN Ao1, GAO Cheng2**
1. College of Chemistry Chemical Engineering, China West Normal University, Nanchong 637009, China; 2. College of Chemistry, Jilin Normal University, Siping 136000, China
Abstract In the current textbooks, when preparing of ferrous hydroxide, a gray-green precipitate appears first, which then turns into a reddish-brown precipitate, with no white precipitate observed. The explanation for the formation of the gray-green precipitate is vague, and the amount of reagents required for the experimental reaction is not quantified. This study explores the principle of the preparation of ferrous hydroxide. A simple oxygen-isolated reaction device is designed using a syringe and a test tube, and the optimal amounts of reagents for the preparation of ferrous hydroxide are quantitatively determined to be 1.0 mL of 0.10 mol/L ferrous sulfate solution and 5.0 mL of 8.00 mol/L sodium hydroxide solution. The experimental results have demonstrated that the true cause of the formation of gray-green precipitates during the preparation of ferrous hydroxide is the hydration reaction between ferrous hydroxide and water, as well as the aggregation state resulting from its own sedimentation. The improved experiment is simple to operate, the white precipitate has a long preservation time, the reproducibility rate is high, and it is convenient for classroom demonstration.
LIU Xi-Peng, CHEN Ao, GAO Cheng. Further Improvement in Preparation Experiment of Ferrous Hydroxide[J]. Chinese Journal of Chemical Education, 2025, 46(11): 94-97.
