Place a coin in dry ice and you’d think there would be no reaction. On the contrary. I don’t quite know what the reaction is and why it happens or why it stops. What has finished happening exactly?
About dry ice:
Dry ice, sometimes referred to as “cardice” (chiefly British chemists), is the solid form of carbon dioxide. It is used primarily as a cooling agent. Its advantages include lower temperature than that of water ice and not leaving any residue (other than incidental frost from moisture in the atmosphere). It is useful for preserving frozen foods, ice cream, etc., where mechanical cooling is unavailable.