What was the function of adding salt to harvested ice during early thermal regulation attempts?

Creating colder mixtures capable of preserving goods for longer durations

In the primitive stages of moving perishables over distances, before engineered cooling existed, innovators utilized natural materials like packed snow or ice harvested in winter. To maximize the thermal effectiveness of this naturally sourced cooling agent, a specific additive was employed: salt. The chemical reaction between salt and ice resulted in a mixture that reached temperatures significantly below the standard melting point of pure water ice. This lowered temperature threshold meant that the preservation environment created by the mixture was substantially colder, allowing perishable goods, such as locally produced meat or fish, to remain unspoiled for extended periods while traveling towards urban markets, thereby directly improving the duration of preservation.