Abstract When using KSCN and a small amount of chlorine water to test for Fe2+in the solution,it was observed that the reacted solution appeared yellow instead of the familiar deep red color. Multiple hypotheses were proposed for the possible causes of abnormal phenomena. Through theoretical analysis and a series of comparative experiments,it was found that when chlorine water is insufficient,chlorine gas can only oxidize a portion of Fe2+. Due to the binding of some SCN- by the remaining Fe2+,the concentration of [Fe(NCS)]2+in the resulting solution decreases,resulting in a yellow solution after the experiment. Through experimental exploration and theoretical analysis,it has been confirmed that Fe2+can form coordination ions with SCN-,which do not appear red and have weak stability. The research conclusion can provide a scientific annotation for understanding the discourse of “Fe2+and SCN-not showing red color”in textbooks.
WU Chao-Hui. Experimental Inquiry of Theoretical Prediction and Evidence Reasoning: Reaction Between Ferrous Ion and Thiocyanide[J]. Chinese Journal of Chemical Education, 2026, 47(5): 119-123.
