Salt, baking soda, and sugar will all act to lower the freezing point of the ice, making it melt quicker than the untouched ice cube. Sand is another common substance that may be seen on the roadway.
One sure-fire way to make the ice in your ice chest last longer is to add a simple household item…salt. Rock salt, to be exact. Much like salt helps freeze ice cream as it churns, it can help the ice in your cooler last longer because salt lowers the freezing point.