Eutectic ice is ice made from salted water, which does not melt readily — the refrigeration medium of insulated transport before mechanical cooling took over. A eutectic solution freezes and melts at a single, constant temperature lower than pure water’s: the salt-water plates in a refrigerated container freeze overnight and then hold the load at a steady chill through the day’s deliveries, melting slowly at their eutectic point. The phase-change physics gives a long, flat temperature plateau — ideal for keeping food cold without power. Dairy rounds, fish vans, and railway catering all ran on eutectic plates in their day. Mechanical refrigeration has largely replaced them, but the principle survives in gel packs and passive cold-chain boxes. Salted ice, melting stubbornly at a fixed point, carrying the cold chain on chemistry.