Study on Spontaneous Combustion Risk of Coin Plating Experiment Residue

Abstract

This study examines the risk of spontaneous combustion caused by the residue of the coin plating experiment. In this study, three cases of recent fires due to the unauthorized disposal of the residues left from coin plating experiments in middle and high schools of the Gangwon-do Province (2017～2018) were analyzed and an experiment to recreate the fire was conducted. As a result of the analysis of the three cases of school fires, it was shown that the students who participated in the coin plating experiment wiped the aqueous solution that spilled onto the table during the procedure as well as the residue of the solution inside the beaker with a tissue and disposed of it on the classroom floor or in a plastic trash can along with the coin that was used. If short, 1 h and 18 min, if long, 8 h and 15 min after the tissues with the residues were thrown away in the trash can, a fire broke out. In addition, when the fire experiment was recreated, in a state where 5 g of sodium hydroxide and 5 g of powdered zinc were partially overlapped, 0.25 ml of water was added. After 20 min since the start of the experiment, a fire occurred as the temperature rose to 549 ℃. In particular, when the coin experiment residue was put on toilet paper and dried for 5 min using a hair dryer, a fire occurred as flames started to appear from the residue. Therefore, in order to prevent fires, it is safe to dispose of the residues after conducting the coin plating experiments in waste incinerator machines. Fire safety education must also be enforced upon teachers who are in charge of instructing chemical experiments at school, and science laboratories must be equipped with automatic fire extinguishing facilities, e.g., trash cans that are placed in the classrooms must be made of steel to ensure complete safety.